Species Status Assessment Report for the Central Texas Mussels: DR AF T False Spike (Fusconaia mitchelli) Texas Fatmucket (Lampsilis bracteata) Texas Fawnsfoot (Truncilla macrodon) Texas pimpleback (Cyclonaias petrina) Version 1.0 April 2018 U.S. Fish and Wildlife Service Region 2 Albuquerque, NM This document was prepared by the U.S. Fish and Wildlife Service’s Central Texas Mussel SSA Core Team (Chris Harper, Ben Kahler, Jacob Lewis, Susan Oetker, Gary Pandolfi, Jennifer Servis, and Charrish Stevens) with contributions by Tracy Diver, Kimberly Horndeski, and Clint Robertson. Note about this draft document April 20, 2018 DR AF T This is a preliminary draft document of the U.S. Fish and Wildlife Service. At this time it is intended for the sole purpose of soliciting reviews from expert peer reviewers selected by the Service, from State and Federal partners with expert knowledge of the species and their habitat, and internal review by Department of Interior staff. It is not intended to solicit comment from the public at large. For information contact Chris_Harper@fws.gov.  Draft Central Texas Mussels SSA Report ii April 2018 TABLE OF CONTENTS Chapter 1. Introduction............................................................................................................................. 1 Chapter 2 - Individual Needs ..................................................................................................................... 4 2.A. Central Texas Mussels - General Individual Needs ................................................................. 4 2.A.1 Taxonomy of Central Texas Mussels.................................................................................... 4 2.A.2 Life History of Central Texas Mussels ................................................................................. 5 2.A.3. Resource (Habitat) Needs of Individuals .............................................................................. 6 2.B Species-Specific Needs of Central Texas Mussels ....................................................................... 9 False spike, Fusconaia mitchelli (Simpson, 1895) ............................................................... 9 2.B.2 Texas fatmucket, Lampsilis bracteata ................................................................................ 12 2.B.3 Texas fawnsfoot, Truncilla macrodon ................................................................................ 15 2.B.4 Texas pimpleback, Cyclonaias petrina ............................................................................... 18 2.C T 2.B.1 Summary ..................................................................................................................................... 21 3.A. AF Chapter 3 - Population And Species Needs ............................................................................................ 22 Historical Range and Distribution............................................................................................... 22 3.A.1 False Spike .......................................................................................................................... 22 3.A.2 Texas Fatmucket .................................................................................................................. 24 3.A.3 Texas Fawnsfoot .................................................................................................................. 26 3.A.4 Texas Pimpleback ................................................................................................................ 28 Needs of Central Texas Mussels ................................................................................................. 30 DR 3.B 3.B.1 Population Resiliency ......................................................................................................... 30 Chapter 4 - River Basins And Sections Of Interest ............................................................................... 36 4.A. Major Central Texas Watersheds - General Current Conditions ................................................ 36 Water and Environmental Flows in Texas .................................................................................. 37 4.B Brazos River and Basin ............................................................................................................... 40 4.B.1 LOWER CLEAR FORK OF THE BRAZOS RIVER ........................................................ 41 4.B.2 Upper Brazos River ............................................................................................................. 41 4.B.3 Little River .......................................................................................................................... 42 4.B.4 Middle/Lower Brazos River................................................................................................ 42 4.C Colorado River and Basin ........................................................................................................... 43 4.C.1 Lower Elm Creek ................................................................................................................ 45 4.C.2 Lower Concho River ........................................................................................................... 45 4.C.3 Upper/Middle San Saba River ............................................................................................ 46 4.C.4 Lower San Saba River (and Middle Colorado River) ......................................................... 46 4.C.5 Llano River ......................................................................................................................... 47 4.C.6 Pedernales River ................................................................................................................. 47 4.C.7 Lower Onion Creek ............................................................................................................. 47 4.C.8 Lower Colorado River ........................................................................................................ 48 4.D. Guadalupe River and Basin......................................................................................................... 49 4.D.1 Upper Guadalupe River ...................................................................................................... 50 4.D.2 Lower Guadalupe River (and Lower San Marcos River) ................................................... 50 4.E Trinity River and Basin ............................................................................................................... 52 Lower East Fork of the Trinity River.................................................................................. 53 4.E.2 Middle Trinity River ........................................................................................................... 54 T 4.E.1 Chapter 5 - Current Conditions .............................................................................................................. 55 5.A General current conditions of Central Texas Mussels ................................................................ 55 5.B AF Methodology for Population Resiliency Assessment .................................................................. 55 False Spike .................................................................................................................................. 56 5.B.1 Current Distribution ............................................................................................................. 56 5.B.2 Areas Presumed Extirpated ................................................................................................. 59 5.B.3 Current Conditions .............................................................................................................. 59 5.C Texas fatmucket, Lampsilis bracteata ........................................................................................ 63 Current Distribution ............................................................................................................. 63 DR 5.C.1 5.C.2 Areas Presumed Extirpated ................................................................................................. 68 5.C.3 Current Conditions of Texas Fatmucket ............................................................................. 68 5.C.4 Current Population Resiliency ............................................................................................ 72 5.C.5 Current Species Representation .......................................................................................... 72 5.C.6 Current Species Redundancy .............................................................................................. 72 5.D Texas fawnsfoot .......................................................................................................................... 72 5.D.1 Current Distribution ............................................................................................................. 72 5.D.2 Areas Presumed Extirpated .................................................................................................. 77 5.D.3 Current Conditions ............................................................................................................... 77 5.D.4 Current Population Resiliency ............................................................................................ 81 5.D.5 Current Species Representation .......................................................................................... 81 5.D.6 Current Species Redundancy .............................................................................................. 81 5.E Texas pimpleback ....................................................................................................................... 81 Draft Central Texas Mussels SSA Report iv April 2018 5.E.1 Current Condition ................................................................................................................ 81 5.E.2 Areas Presumed Extirpated ................................................................................................. 86 5.E.3 Current Conditions of Texas Pimpleback ........................................................................... 86 5.E.4 Current Population Resiliency ............................................................................................ 90 5.E.5 Current Species Representation .......................................................................................... 90 5.E.12 Current Species Redundancy .............................................................................................. 90 5.F Summary of current conditions of Central Texas Mussels ......................................................... 90 Chapter 6 - Factors influencing viability ................................................................................................ 91 Increased fine sediment ........................................................................................................... 91 6.A.2 Changes in water quality ......................................................................................................... 92 6.A.3 Altered Hydrology - Inundation .............................................................................................. 92 6.A.4 Altered Hydrology – Flow Loss and Scour............................................................................. 93 6.A.5 Predation, Collection, Disease, and Invasive Species ............................................................. 95 6.A.6 Barriers to fish movement ....................................................................................................... 96 6.A.7 Climate Change ....................................................................................................................... 96 6.A.8 Management Actions ............................................................................................................... 97 6.A.9 Summary ................................................................................................................................. 97 AF T 6.A.1 Chapter 7 - Viability And Future Conditions ........................................................................................ 98 Introduction ................................................................................................................................ 98 7.B. Future Scenarios and Considerations .......................................................................................... 99 DR 7.A 7.B.1 Scenario 1.......................................................................................................................... 103 7.B.2 Scenario 2.......................................................................................................................... 103 7.B.3 Scenario 3.......................................................................................................................... 105 7.B.4 Scenario 4.......................................................................................................................... 105 7.C Viability (Resiliency, Redundancy, and Representation) ......................................................... 113 7.C.1. Scenario 1 .......................................................................................................................... 113 7.C.2. Scenario 2 .......................................................................................................................... 115 7.C.3. Scenario 3 .......................................................................................................................... 118 7.C.4. Scenario 4 .......................................................................................................................... 120 7.D Status Assessment Summary .................................................................................................... 122 7.E SUPPLEMENTARY TABLES AND FIGURES ..................................................................... 124 summary of future population conditions by river basin....................................................................... 124 summary of future population condition by species.............................................................................. 124 Draft Central Texas Mussels SSA Report v April 2018 Appendix A - Literature Cited .................................................................................................................. A-1 Appendix B – Evaluating Causes and Effects of Stressors for Central Texas Mussels Species Status Assessment................................................................................................................................................ B-1 Appendix C - Future Condition Tables for Central Texas Mussels .......................................................... C-1 C.1. False Spike ..................................................................................................................................... C-1 C.1.a Scenario 1 ................................................................................................................................. C-1 C.1.b Scenario 2................................................................................................................................. C-2 C.1.c Scenario 3 ................................................................................................................................. C-3 C.1.d Scenario 4................................................................................................................................. C-4 C.2. Texas Fatmucket ............................................................................................................................ C-5 T C.2.a Scenario 1 ................................................................................................................................. C-5 C.2.b Scenario 2................................................................................................................................. C-7 C.2.c Scenario 3 ................................................................................................................................. C-8 AF C.2.d Scenario 4................................................................................................................................. C-9 C.3. Texas Fawnsfoot .......................................................................................................................... C-10 C.3.a Scenario 1 ............................................................................................................................... C-10 C.3.b Scenario 2............................................................................................................................... C-11 C.3.c Scenario 3 ............................................................................................................................... C-12 C.3.d Scenario 4............................................................................................................................... C-13 DR C.4. Texas pimpleback ........................................................................................................................ C-14 C.4.a Scenario 1 ............................................................................................................................... C-14 C.4.b Scenario 2............................................................................................................................... C-16 C.4.c Scenario 3 ............................................................................................................................... C-17 C.4.d Scenario 4............................................................................................................................... C-18 Appendix D– results by population ....................................................................................................... D-1 D.1 FALSE SPIKE .......................................................................................................................... D-1 D.2 TEXAS FATMUCKET ............................................................................................................ D-4 D.3 TEXAS FAWNSFOOT ............................................................................................................ D-9 D.4 TEXAS PIMPLEBACK ......................................................................................................... D-14 Appendix E - Glossary Of Terms Used In This Document ................................................................. E-1       Draft Central Texas Mussels SSA Report vi April 2018 CHAPTER 1. INTRODUCTION The Species Status Assessment (SSA) framework supports an in-depth review of the species biology and threats, an evaluation of its biological status, and an assessment of the resources and conditions needed to maintain long-term viability (Service 2016, entire). The intent is for the SSA Report to be easily updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment to Listing to Consultations to Recovery (if warranted). As such, the SSA Report will be a living document upon which other documents, such as possible listing rules, recovery plans, and 5-year reviews, would be based for those species warranting protections under the Act, should they become listed. AF T This SSA Report (version 1.0) provides a review of the ecological needs and current condition of four species of freshwater mussels (Family Unionidae) endemic to the central Texas region in the Brazos, Colorado, Guadalupe, and Trinity River basins. This SSA Report will refer to the species collectively as “Central Texas mussels” and individually by common name and by scientific name (i.e., genus and specific epithet), where appropriate. The U.S. Fish and Wildlife Service (Service) is responsible for identifying those species that are in need of protection under the Endangered Species Act of 1973, as amended (Act). The Service will be making a determination on whether these four species of freshwater mussels warrant protections under the Act. DR The false spike (Fusconaia mitchelli) is a petitioned species with a positive 90-day finding under the Act (USFWS 2009, entire). The Service is required to conduct a status review and complete a 12-month finding to determine whether or not listing under the Act is warranted. The Texas fatmucket (Lampsilis bracteata), Texas fawnsfoot (Truncilla macrodon), and Texas pimpleback (Cyclonaias petrina, formerly classified as Quadrula petrina) are all candidate species with warranted 12-month findings under the Act (USFWS 2011, entire). These species have been candidates for listing since 2011. The Service is required to make a final determination of whether these three species warrant listing under the Act. A candidate is a species for which we have on file sufficient information on biological vulnerability and threats to support a proposal to list as endangered or threatened but is precluded by higher priority listing actions. Previous status reviews indicated that these three freshwater mussel species face threats including impoundments, sedimentation, habitat loss, and riverbank destabilization.     Draft Central Texas Mussels SSA Report 1 April 2018 For the purpose of this assessment, we generally define viability as the ability of the Central Texas mussels to sustain populations in natural river systems over time. Using the SSA framework (Figure 1.1), we consider what the species need to maintain viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation (i.e., the 3Rs, Smith et al. 2018, entire). The 3Rs are defined as: Resiliency describes the ability of populations to withstand stochastic disturbance. Generally speaking, populations need abundant individuals within habitat patches of adequate area and quality to maintain survival and reproduction in spite of disturbance. We can measure resiliency based on metrics of population health; for example, birth versus death rates and Figure 1.1 Species Status Assessment Framework population size. Highly resilient (US Fish and Wildife Service 2016). populations are better able to withstand disturbances such as random fluctuations in birth rates (demographic stochasticity), variations in rainfall (environmental stochasticity), or the effects of anthropogenic activities. AF T  Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resiliency, and their distribution (and connectivity), redundancy gauges the probability that the species has a margin of safety to withstand or can bounce back from catastrophic events (such as a rare destructive natural event or episode involving many populations).  Representation describes the ability of a species to adapt to changing environmental conditions over time. Representation can be measured by the breadth of genetic or environmental diversity within and among populations and gauges the probability that a species is capable of adapting to environmental changes. The more representation, or diversity, a species has, the more it is capable of adapting to changes (natural or human-caused) in its environment. In the absence of speciesspecific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat characteristics across the geographical range. DR  To evaluate the biological status of the Central Texas mussels both currently and into the future, we assessed a range of conditions to allow us to consider the species’ resiliency, redundancy, and representation (together, the 3Rs). This SSA Report provides a thorough assessment of biology and Draft Central Texas Mussels SSA Report 2 April 2018 natural history of these species and assesses demographic risks, stressors, and limiting factors in the context of determining the viability and risks of extinction for the species. The format for this SSA Report includes: the resource needs of individuals (Chapter 2), populations and species (Chapter 3); the Central Texas mussels’ historical distribution and a framework for determining the distribution of resilient populations across its range for species viability (Chapter 3); a review of the current, and past management of water resources in Texas generally, and specifically, for each river basin (Chapter 4); determining which of the risk factors affect the species’ viability and to what degree (Chapter 5); reviewing the likely causes of the current and future status of the species (Chapter 6); and concluding with a description of the viability in terms of resiliency, redundancy, and representation (Chapter 7). This document is a compilation of the best available scientific and commercial information and a description of past, present, and likely future risk factors to the Central Texas mussels.   DR   AF T Appendix A includes all references cited, which are available upon request, in portable document format (pdf), from the Austin, Texas Ecological Services Field Office1. Appendix B contains Cause and Effects Tables, which evaluate the stressors to the species historically and into the future. Appendix C contains detailed tables of the results of our analysis, and Appendix D describes the results by population. Finally, Appendix E contains a glossary of terms used in this SSA Report; these terms are indicated in bold text throughout the document.                                                                   1 10711 Burnet Road, Suite 200, Austin, Texas, 78758 or call 512-490-0057 Draft Central Texas Mussels SSA Report 3 April 2018 CHAPTER 2 ‐ INDIVIDUAL NEEDS This chapter reviews the basic biological and ecological information about the four species of Central Texas mussels. This information includes taxonomy, phylogenetic relationships, morphology, and a description of known life history traits, with an emphasis on those life history traits that are important to this analysis. We then outline the resource needs at the level of the individual. Basic information is included about freshwater mussels in general, to the Central Texas mussels in particular, and to individual species where appropriate. 2.A. CENTRAL TEXAS MUSSELS ‐ GENERAL INDIVIDUAL NEEDS   T 2.A.1 TAXONOMY OF CENTRAL TEXAS MUSSELS AF Each of the four species of Central Texas mussels belong to Family Unionidae, also known as the naiads and pearly mussels, a group of bivalve mollusks known to have been in existence for over 400 million years (Howells et al. 1996, p.1) and now representing over 1000 species worldwide and over 300 species in North America (Strayer et al. 2004, p.429). This report follows the most recently published and accepted taxonomic treatment of North American freshwater mussel as provided by Williams et al. (2017, entire) and applies in common to each of the four species of Central Texas mussels assessed in this report. Mollusca Linnaeus, 1758 Bivalvia Linnaeus, 1758 Unionida Gray, 1854 Unionidae Rafinesque, 1820 Ambleminae Rafinesque, 1820 DR PHYLUM CLASS ORDER FAMILY SUBFAMILY Each of the four species of Central Texas mussels, along with approximately 85% of North American mussel species, belongs to the subfamily Ambleminae, members of which generally share the following common characteristics: (1) are typically slow growing and commonly live for more than twenty years, with growth rates typically between 1-5mm/year, depending on conditions (Howells et al. 1996, p.17), (2) are frequently summer breeders (Howells et al. 1996, p. 9), (3) possess either unhooked or axe-head-type glochidia; may brood larvae in either all four or the outer two (lateral) demibranchs (McMahon and Bogan 2001, p. 342), (4) glochidia attach primarily to gills (Barnhart et al. 2008, p. 375), (5) produce and store conglutinates in their mantle to facilitate rapid discharge of glochidia when fish attempt to feed (Barnhart et al. 2008, p. 375) and (6) free glochidia (not attached) may appear in drift, i.e., are exposed to free water prior to host infestation, for hours to weeks (Barnhart et al. 2008, p. 375). Draft Central Texas Mussels SSA Report 4 April 2018 2.A.2 LIFE HISTORY OF CENTRAL TEXAS MUSSELS AF T Freshwater mussels, including the Central Texas mussels, have a complex life history (Figure 2.1) involving an obligate parasitic larval life stage, called glochidia, which are wholly dependent on host fish. As freshwater mussels are generally sessile, dispersal is accomplished primarily through the behavior of host fish and their tendencies to travel upstream and against the current (positive rheotaxis) in rivers and streams. Mussels are broadcast spawners; males release sperm into the water column, which is taken in by the female through the incurrent siphon (the tubular structure used to draw water into the body of the mussel). The sperm fertilizes the eggs, which are held during maturation in an area of the gills called the marsupial chamber. The developing larvae remain in the marsupial chamber until they mature and are ready for release as glochidia, to attach on the gills, head, or fins of fishes (Vaughn and Taylor 1999, p. 913). Glochidia die if they fail to find a host fish, attach to a fish that has developed immunity from prior infestations, or attach to the wrong location on a host fish (Neves 1991, p. 254; Bogan 1993, p. 599). Glochidia encyst (enclose in a cyst-like structure) on the host’s tissue, draw nutrients from the fish, and develop into juvenile mussels weeks or months after attachment (Arey 1932, pp. 214–215). The glochidia will remain encysted for about a month through a transformation to the juvenile stage. Once transformed, the juveniles will excyst from the fish and drop to the substrate. Freshwater mussel species vary in both onset and duration of spawning, how long developing larvae are held in the marsupial gill chambers (gills utilized for holding eggs and glochidia), and which fish species serve as hosts. The mechanisms employed by mussel species to increase the likelihood of interaction between host fish and glochidia vary by species. DR Mussels are generally immobile but experience their primary opportunity for dispersal and movement within the stream as glochidia attached to a mobile host fish (Smith 1985, p. 105). Upon release from the host, newly transformed juveniles drop to the substrate on the bottom of the stream. Those juveniles that drop in unsuitable substrates die because their immobility prevents them from relocating to more favorable habitat. Juvenile freshwater mussels burrow into interstitial substrates and grow to a larger size that is less susceptible to predation and displacement from high flow events (Yeager et al. 1994, p. 220). Adult mussels typically remain within the same general location where they dropped off (excysted) of their host fish as juveniles. Host specificity can vary across mussel species, which may have specialized or generalized relationships with one or more taxa of fish (and in one case, salamanders). Mussels have evolved a wide variety of adaptations to facilitate transmission of glochidia to host fish including: display/mantle lures mimicking fish or invertebrates, packages of glochidia (conglutinates) that mimic worms, insect larvae, larval fish, or fish eggs, and release of glochidia in mucous webs that entangle fish (Strayer et al. 2004, p. 431). Polymorphism of mantle lures and conglutinates frequently exists within mussel populations (Barnhart et al. 2008, p. 383), representing important adaptive capacity in terms of genetic diversity and ecological representation. Freshwater mussels can be long-lived and slow-growing (but see Haag and Rypel 2010, p. 2), and individuals have been estimated to have been decades to centuries old (Strayer et al. 2014, p. 433). In part, because of their long life spans, recruitment is episodic, and populations may be slow to recover from disturbance. Thin-shelled mussels (like Truncilla spp.) often live 4-10 years while thick-shelled mussels (like Quadrula spp.) can live for 20-40 years, or longer (Howells et al. 1996, p.17). Draft Central Texas Mussels SSA Report 5 April 2018 DR AF T Fast-growing species (like Lampsilis spp.) may mature as early as their first year, while slow-growing species (like Quadrula spp.) may take as long as 5-20 years to mature (Haag and Rypel 2010, p. 19), and fast-growing short-lived species may be better adapted to more variable environments and better suited to recovering from high-mortality events than slower-growing longer-lived species that may be better adapted to more stable environments (Haag and Rypel 2010, p. 20). With that said, growth rates and longevity can be expected to vary somewhat within and among populations. Figure 2.1. Generalized freshwater mussel life cycle. (Image courtesy Shane Hanlon, USFWS.) 2.A.3. RESOURCE (HABITAT) NEEDS OF INDIVIDUALS Here we describe general habitat needs common to each of the four Central Texas mussel species. We describe the specific needs of each species in section 2.B (Species-Specific Needs of Central Texas Mussels). The four species of Central Texas mussels generally occur in medium to large streams and rivers and require adequate amounts of flowing water, free of contaminants and water quality impairments and having adequate food supply, with refugia from both high- and low-flow events, appropriate substrate that is generally characterized as stable and free of excessive fine sediment, access to appropriate fish hosts, Draft Central Texas Mussels SSA Report 6 April 2018 and habitat connectivity (i.e., lack of excessive impoundments and barriers to fish passage) (Figure 2.2). The four species of Central Texas mussels are generally not adapted to lentic environments (such as ponds, reservoirs, and impoundments) and, with few exceptions, do not persist and thrive in habitats that are not free-flowing (lotic, such as unimpeded stream and river reaches). Following are the broad categories of habitat needs of the species, which are also summarized in Table 2.1. AF T Flowing water and protection from low-flow (dewatering) events. The four species of Central Texas mussels are adapted to free-flowing rivers and streams (lotic environments). As such, they require unaltered rivers and streams, free from major impoundments and other structures that create a nonflowing (lentic) environment. Free-flowing water provides appropriate oxygenation, nutrition, thermal buffering, and access to fish hosts for reproduction and dispersal. Central Texas mussels require adequate, but not excessive flows which may lead to scouring of suitable substrates. Central Texas mussels generally do not tolerate exposure to a non-watered environment (i.e., a lack of water and increased water and air temperature approaching or exceeding lethal thresholds) and dewatering can lead to reduced reproduction, health, body condition, fitness, and can result in eventual death of stranded mussels. As such, Central Texas mussels require habitats and meso-habitats that provide some minimum flows and protections from dewatering throughout the year. Central Texas mussels do not persist in habitats and meso-habitats that are subject to rapid and frequent dewatering events. DR Water quality. The four species of Central Texas mussels are sensitive to contaminants and water quality impairments and require clean water free from contaminants and water quality impairment. Water quality impairments include the presence of excessive nutrients such as ammonia (NH3), which is highly toxic to aquatic organisms, other chemicals including chlorine (Cl), pollutants including heavy metals (Cu, Cd, Hg), dissolved salts (salinity), and organic contaminants like pesticides and herbicides, and may affect each life stage of freshwater mussels (Cope et al. 2018, p. 452). High-quality water has appropriate oxygenation (expressed as dissolved oxygen, DO), and provides appropriate thermal requirements for the Central Texas Mussels; both elevated and depressed water temperatures also represent water quality impairments. Elevated suspended solids and sediments (expressed as TSS or as turbidity) can also impair water quality with adverse effects to freshwater mussels (Gascho-Landis and Stoeckel 2015, p. 8). Protection from high-flow (scour) events. The four species of Central Texas mussels live in the substrate of the benthic environment (stream bed and bank habitats) and these sediments and cobble are subject to periodic disturbance as the substrate (and any mussels) is scoured and transported downstream to locations that may or may not be suitable. As such, Central Texas mussels require microhabitats (flow refugia) that are naturally protected from scouring high-flow events that may occur during flood conditions. Some examples of flow refugia include boulders, crevices, and bedrock shelves, bends, meanders, undercut banks, eddies, riffles, and living or dead vegetation (i.e., tree roots and coarse woody debris). Central Texas mussels require adequate flows. Excessive flows can result in scouring of substrate, degrading or destroying habitats. Firm and stable substrate. Central Texas mussels live in the substrate of the benthic environment (stream bed and bank habitats) and these sediments and cobble are subject to periodic disturbance as the substrate (and any mussels) are scoured and transported downstream to a location that may or may not be suitable. Sediments including shifting sands and unconsolidated silts generally do not provide appropriate anchoring substrate, and thus appropriate habitat, for Central Texas mussels. Draft Central Texas Mussels SSA Report 7 April 2018 Nutrition and food supply. Adult freshwater mussels, including Central Texas mussels, are filter-feeders, siphoning suspended phytoplankton, zooplankton, rotifers, protozoans, detritus and dissolved organic matter from the water column (Strayer et al. 2004, p. 430) and from sediment; juvenile mussels are capable of using their feet to collect food items from sediments (pedal feeding; Vaughn et al. 2008, pp. 409-411). Glochidia derive what little nutrition they need from their obligate fish hosts. AF T Fish hosts. Central Texas mussels have an obligate parasitic relationship with their respective host fishes. Central Texas mussels cannot successfully reproduce or disperse in the absence of appropriate host fish. Host fish are necessary to facilitate downstream dispersal and represent the only mechanism to achieve upstream dispersal in a free-flowing environment. DR Figure 2.2. Central Texas mussel population needs. Table 2.1. Generalized life history and resource needs of Central Texas mussels. Life Stage Resource Need(s) - Habitat Requirements Gamete ● (broadcast sperm, egg development, to fertilization) ● Glochidium ● (from attachment through excystment) ● Reference(s) High-quality water having an absence of a high total suspended sediment (TSS) load and without toxicants Appropriate water temperature and food availability Gascho-Landis and Stoeckel 2015, p. 8 Cope et al. 2008, p. 454 Galbraith and Vaughn 2009, p. 12 Presence of appropriate host fish (for attachment, encystment and upstream dispersal) High water quality and lack of contaminants Barnhart et al. 2008, p. 372 Draft Central Texas Mussels SSA Report 8 Augspurger et al. 2003, p. 2571 April 2018 ● ● ● (from excystment through maturity) ● ● ● ● Adult ● ● (Maturity) ● ● ● ● Augspurger et al. 2003, pp. 2571, 2574 Augspurger et al. 2003, p. 2569 Cope et al. 2008, p. 456 Flow refuges Appropriate substrate (for burrowing) Dissolved oxygen >3 ppm Appropriate food source Water temperature <40C (104F) Flowing water Adequate dissolved minerals (Ca) to support shell growth AF ● Flow refuges Appropriate substrate (for burrowing) Low salinity Low ammonia levels (below 0.3-0.7 mg/L NH3-N at pH 8) Low levels of copper (and other metals) and other contaminants (chlorine) Dissolved oxygen > 1.3ppm Flowing water T Juvenile and subadult 2.B SPECIES‐SPECIFIC NEEDS OF CENTRAL TEXAS MUSSELS 2.B.1 FALSE SPIKE, FUSCONAIA MITCHELLI (SIMPSON, 1895) 2.B.1. A T AXONOMIC AND M ORPHOLOGICAL D ESCRIPTIONS DR The false spike was originally described as the species Unio mitchelli by Charles T. Simpson in 1895 from the Guadalupe River in Victoria County, Texas (Dall 1896, pp. 5-6). A similar species, Unio iheringi was described as a new species by Berlin H. Wright in 1898 from the San Saba River (a tributary of the Colorado) in Menard County, Texas (Wright 1898, p.93). This taxon was recognized as a form of Unio mitchelli var. iheringi by Simpson in 1914 (pp. 622-3). Strecker (1931) synonymized Unio mitchelli (from the Guadalupe River) and Unio iheringii (from the San Saba River) and treated false spike as Elliptio tamaulipasensis2 and noted it “a variable species with long and short, compressed and inflated forms living in the same stream” and found in the Brazos, Colorado, and Guadalupe systems from locations including the Leon River in Bell and Coryell Counties, Guadalupe River in Comal, Kendall, Kerr and Victoria Counties, Llano River in Mason County, and the San Saba River in Menard County (Strecker 1931, pp. 18-19).                                                                   2 Howells et al. (1996, pp. 127-8) and Howells (2014, pp. 85-86) treated Sphenonaias taumilpana as a synonym of false spike and included the Rio Grande basin of Texas and New Mexico within the historic range of false spike. However, Pfeiffer et al. (2016, p. 285, 289) reject that treatment and instead follow Graf and Cummings (2007, p. 309), who treat Sphenonaias taumilapana is a separate species endemic to the Rio Grande drainage (and distinct from F. mitchelli), “known only from fossil specimens” and having “much larger” shells than F. mitchelli in Central Texas. As such, this report does not include the Rio Grande drainage as part of the historical range of the false spike, Fusconaia mitchelli. Draft Central Texas Mussels SSA Report 9 April 2018 The false spike has been assigned as Quincuncina mitchelli by Turgeon et al. (1988, p. 33) as it was recognized by Howells et al. (1996, p. 127) as Quadrula mitchelli by Haag (2012, p. 71), and as Fusconaia mitchelli by Pfeiffer et al. where it was reported as “an endemic to the Guadalupe, Colorado, and Brazos drainages of Central Texas” (2016, p. 289). The current recognized scientific name for false spike is Fusconaia mitchelli, and this report refers to it as such. The following taxonomic treatment follows Williams et al. (2017, pp. 35, 39). Bivalvia Linnaeus, 1758 Unionida Gray, 1854 Unionidae Rafinesque, 1820 Ambleminae Rafinesque, 1820 Pleurobemini Hannibal, 1912 Fusconaia Simpson, 1900 Fusconaia mitchelli Simpson, 1895 (reassigned from Quincuncina) T CLASS ORDER FAMILY SUBFAMILY TRIBE GENUS SPECIES DR AF The false spike is a medium-sized freshwater mussel (to 132 mm) with a yellow-green to brown, to black, elongate shell, sometimes with greenish rays (Figure 2.3). For a detailed description see Howells et al. 1996 (pp. 127-8) and Howells 2014 (p. 85). Figure 2.3. Adult false spike from the Llano River, Mason County, Texas. (Photo courtesy Gary Pandolfi, USFWS.) Draft Central Texas Mussels SSA Report 10 April 2018 2.B.1. B G ENETIC D IVERSITY Pfeiffer et al. (2016, pp. 287-288; Fig.2, p. 284) presented preliminary information that false spike may be endemic just to the Guadalupe River basin, while false spike from the Colorado and Brazos River basins may be a new species (Fusconaia iheringi), but he stopped short of concluding that F. iheringi should be recognized as a separate species at this time. As such, this report considers all three clades (the Brazos, Colorado, and Guadalupe River basins) as false spike (Fusconaia mitchelli). 2.B.1. C R EPRODUCTION AND F ISH H OST I NTERACTIONS Pfeiffer et al. (2016, p. 287) suggested that, based on closely related species, false spike likely brood eggs and larvae from early spring to late summer and that host fish are expected to be minnows (family Cyprinidae). Howells et al. (1996, pp. 127-8) and Howells (2014, p. 85) report the fish hosts as unknown. AF T Members of the tribe Pleurobemini produce conglutinates (Barnhart et al. 2008, p. 376) and tend to exhibit short-term brooding (tachytictia), that is, they release glochidia soon after the larvae mature (Barnhart et al. 2008, p. 384). Conglutinates may be important in protecting glochidia from some water quality contaminants (Barnhart et al. 2008, p. 375), serving as barriers as glochidia physically encased in conglutinates, rather than free-floating, are not directly exposed to waterborne contaminants (including metals such as copper; Gillis et al. 2008, pp.138, 144). Similar physical protection is also afforded to glochidia when they encyst on host fish. 2.B.1. D A GE AND G ROWTH DR Congeners (Fusconaia spp.) from the southeast United States are reported by Haag and Rypel (2010) to reach a maximum age of 15-51 years (Table 1, pp. 4-6) and members of tribe Pleurobemini ranged from 14-57 years (p. 10). No age at maturity information exists for this species (Howells 2010d, p. 3). 2.B.1. E H ABITAT False spike occurs in larger creeks and rivers with sand, gravel, or cobble substrates, and with slow to moderate flows, and is not known from impoundments, nor from deep waters (Howells 2014, p. 85) (Table 2.2). Draft Central Texas Mussels SSA Report 11 April 2018 Table 2.2. False Spike Life History and Resource Needs Life Stage Resource Needs  Obligate ectoparasite of fish gills. Glochidia through  Specific host fish unknown. host fish attachment Reference Morton et al. 2016, p. 4 Haag 2012, p. 41  Habitat associations remain undescribed, although likely similar to adult needs. Morton et al. 2016, p. 4 Howells et al. 2010, p. 8 of 122 Adults  Large rivers and creeks in flowing water with gravel-cobble substrates, mainly riffle and run mesohabitats. Not known to occur in impoundments or reservoirs. Phytoplankton, algae, and detritus for food. Water temperature <40 º Celsius (104º Fahrenheit). Morton et al. 2016, p. 4 Howells 2014, p. 85 Randklev et al. 2013, p.1819 Randklev et al. 2012, p. 1  AF  T Juveniles -Excystment through sexual maturity 2.B.2 TEXAS FATMUCKET, LAMPSILIS BRACTEATA 2.B.2. A T AXONOMIC AND M ORPHOLOGICAL D ESCRIPTION DR The Texas fatmucket was originally described as the species Unio bracteatus by A.A. Gould in 1855 from the “Llanos River” in “Upper” Texas (p. 228). Simpson (1900, p. 543) placed the species in the genus Lampsilis and noted the species occurred in the Llanos (sic), Guadalupe, and Colorado rivers of Texas. Simpson later recognized the species as Lampsilis bracteata (1914, pp. 73-74). Strecker (1931, p.39) recognized Texas fatmucket as Lampsilis bracteata, and that it was “characteristic of the Guadalupe and Colorado river systems.” The recognized scientific name for Texas fatmucket is Lampsilis bracteata, and this report refers to it as such. The following taxonomic treatment follows Williams et al. (2017, pp. 35, 39). CLASS ORDER FAMILY SUBFAMILY TRIBE GENUS SPECIES Bivalvia Linnaeus, 1758 Unionida Gray, 1854 Unionidae Rafinesque, 1820 Ambleminae Rafinesque, 1820 Lampsilini Ihering, 1901 Lampsilis Rafinesque, 1820 Lampsilis bracteata Gould, 1855 The Texas fatmucket is a small to medium-sized freshwater mussel (to 100 mm) that exhibits sexual dimorphism and has a yellow-green-tan elliptical to subrhomboidal shell with “black or brown rays that broaden near the margin and are often broken.” Females have variable mantle flaps that are used as lures; for a detailed description see Howells et al. 1996 (p. 61) and Howells 2014 (p. 41) (Figure 2.4). Draft Central Texas Mussels SSA Report 12 April 2018 T AF Figure 2.4. Male (left) and female (right) Texas fatmucket from the San Saba River, Menard County, Texas. (Photo courtesy Gary Pandolfi, USFWS.) DR 2.B.2. B G ENETIC D IVERSITY Hannes (2017) investigated species relationships in the genus Lampsilis and found that L. bracteata was a separate and distinct species from L. hydiana (Louisiana fatmucket), a species having a similar appearance but little overlap in range (p. 18). Hannes (2017, p. 8-18) analyzed four L. bracteata specimens (collected from the Llano River in Kimble County and the San Saba River in Menard County p.8) and found that they shared the same haplotype (p. 18) but acknowledges that some genetic diversity may exist and is expressed as “ecophenotypes” (p. 18) with some having more elongate shells, and with variation in mantle lures as described by Howells et al. (2011, pp. 1-3), with individuals from different parts of the Colorado River basin having noticeably different mantle flaps/lures. Given the importance of glochidia attachment in the mussel life cycle, mantle lure polymorphism is an important component of genetic/environmental diversity, adaptive potential, and thus, representation for the Texas fatmucket. Recently, Inoue et al. (2018; pp. 6-7) found that Texas fatmucket in the Guadalupe River basin are more closely related to L. hydiana than to L. bracteata, and are likely a new species. In this report, we include the populations in the Guadalupe River basin in our analysis but acknowledge they are likely not Texas fatmucket. Draft Central Texas Mussels SSA Report 13 April 2018 2.B.2. C R EPRODUCTION AND F ISH H OST I NTERACTIONS Host fishes are known to be members of the Family Centrarchidae (sunfishes) including: bluegill (Lepomis macrochirus), green sunfish (Lepomis cyanellus), Guadalupe bass (Micropterus treculii), and largemouth bass (Micropterus salmoides) (Howells 1997, p. 257; Johnson et al. 2012, p. 148; Howells 2014, p. 41; Ford and Oliver, p. 4). Members of the Lampsilini tribe can expel conglutinates and are known to use mantle lures (Barnhart et al. 2008, p.377) to attract sight feeding fishes that attack and rupture the marsupium, becoming infested by glochidia (p. 380). These species are long-term brooders (bradytictic) (p. 384). 2.B.2. D A GE AND G ROWTH AF T Congeners (Lampsilis spp.) from the southeast United States are reported by Haag and Rypel (2010) to reach a maximum age of 13-25 years (Table 1, p. 4-6) and members of tribe Lampsilini ranged from 4-50 years (p. 10) with a higher growth rate compared to other tribes (p. 15). Louisiana fatmucket (Lampsilis hydinia) has been reported mature at 36.4 mm, and presumably, Texas fatmucket is similar, (Howells 2010, p. 68). No age at maturity information exists for this species (Howells 2010c, p. 3). In the Llano River, recent studies indicate that population structure is 0.5 males to every female (of n=72 sampled), at one sampling location. Additionally, from one sampling location in the San Saba River the sex ratio was 1.3 males per female mussel (of n=87 sampled) (Seagroves and Schwalb 2017, p. 11) During peak reproduction months (February through July) the Llano River showed glochidia viability averaging 80% whereas the San Saba glochidia viability averaged 81% (Seagroves and Schwalb 2016, p. 12). DR 2.B.2. E H ABITAT The Texas fatmucket occurs in flowing streams and rivers of the Edwards Plateau with substrates of “firm mud, stable sand, and gravel bottoms, in shallower waters” sometimes in bedrock fissures or among roots of bald cypress (Taxodium distichum) and other aquatic vegetation (Howells 2014, p. 41) (Table 2.3). Draft Central Texas Mussels SSA Report 14 April 2018 Table 2.3. Life History and Resource Needs of Texas Fatmucket Life Stage Resource Needs Reference Glochidia through host fish attachment  Known host fishes include bluegill, green sunfish, largemouth bass, and Guadalupe bass, while other hosts in the family Centrarchidae possible. Johnson et al. 2012, p. 1 Juveniles -Excystment through ~36 mm  Habitat associations remain undescribed, although likely similar to the needs of adults. Howells 2010a, p. 3 Adults  Bank and pool habitat in moderate to small sized streams in flowing waters. Typically occur in finer substrates of mud, sand, and gravel in relatively shallow waters. Occasionally known to occur in sediment-filled bedrock crevices and fissures. Individuals also documented from aquatic macrophytes (in beds of submerged vegetation) that retain and stabilize suitable substrates. Randklev et al. 2017c, p. 40   T Howells 2010a, p. 3 AF  2.B.3 TEXAS FAWNSFOOT, TRUNCILLA MACRODON 2.B.3. A T AXONOMIC AND M ORPHOLOGICAL D ESCRIPTIONS DR The Texas fawnsfoot was originally described as the species Unio macrodon by Isaac Lea in 1859 from a location near Rutersville, Fayette County, Texas (pp. 154-5); with shell morphology described by Lea (1862, pp. 192-3). Strecker (1931, p. 48) recognized Texas fawnsfoot as Truncilla macrodon and noted “is an abundant shell in the Colorado and Brazos rivers” with “largest examples from Austin and Waco” and that “adult shells from many of the tributary streams average much smaller” and provided locations in the Brazos River in Brazos and Robertson Counties, Colorado River in Burnet, Colorado, Travis (at Austin) and Wharton Counties, Leon River in Coryell County, Aquilla Creek in McLennan County, Bosque River in McLennan County, North Bosque River in McLennan County, and Llano River in Mason County. Howells et al. (1996) included the Trinity River drainage within the range of Truncilla macrodon (p. 143) and Johnson (1999), in an attempt to revise the genus Truncilla, presented T. macrodon as a synonym of fawnsfoot (T. donaciformis) (p. 6) and described difficulty in distinguishing between the two based on shell morphology (pp. 38-41, 64-65). The combining of the two species was not widely accepted, and recent information suggests that Truncilla macrodon may occur in the Trinity River (Randklev et al. 2017a, p. 11). Recent evidence indicates that individuals identified as Truncilla donaciformis in the Trinity River are actually Truncilla macrodon, with the largest Trinity River population occurring in the middle sections near Oakwood, Texas (Randklev et al. 2017a, p. 11; Inoue et al. 2018, p. 6). Thus, this analysis will include Trinity River populations of T. macrodon. Draft Central Texas Mussels SSA Report 15 April 2018 The recognized scientific name for Texas fawnsfoot is Truncilla macrodon, and this report refers to it as such. The following taxonomic treatment follows Williams et al. (2017, pp. 35, 44). CLASS ORDER FAMILY SUBFAMILY TRIBE GENUS SPECIES Bivalvia Linnaeus, 1758 Unionida Gray, 1854 Unionidae Rafinesque, 1820 Ambleminae Rafinesque, 1820 Lampsilini Ihering, 1901 Truncilla Rafinesque, 1819 Truncilla macrodon Lea, 1859 DR AF T Texas fawnsfoot is a small- to medium-sized (60 mm) mussel with a compressed, elongate oval shell that is “dull green, tan, yellow-brown, reddish-brown with patterns of broken rays, often with irregular blotches, inverted [chevrons] or zig-zag markings, sometimes between rays” (Howells 2014, p. 111) (Figure 2.5); for a more detailed description see Howells et al. 1996 (p. 143) and Howells 2014 (p. 111). Figure 2.5. Multiple size individuals of Texas fawnsfoot, Truncilla macrodon, from the Brazos River, Falls County, Texas. (Photo courtesy Mark Fisher, Texas Department of Transportation.) Draft Central Texas Mussels SSA Report 16 April 2018 2.B.3. B G ENETIC D IVERSITY Genetic analysis of haplotype networks of Truncilla species in Texas indicates that there is no gene flow between Texas fawnsfoot populations in the three major river basins in which it occurs: the Colorado, Brazos, and Trinity rivers (Inoue et al. 2018, p. 4). Each of the three basins likely represents ecologically significant units, of a single species. Therefore, this report recognizes Texas fawnsfoot (Truncilla macrodon) as occurring in the Brazos, Colorado, and Trinity River basins of Texas. 2.B.3. C R EPRODUCTION AND F ISH H OST I NTERACTIONS T Host fishes are unknown for the Texas fawnsfoot but assumed to be freshwater drum (Aplodinotus grunniens; Howells 2014, p. 111). Other Truncilla species occurring in Texas, and elsewhere, are known to use freshwater drum and also sauger (Sander canadensis, Percidae; which does not occur in Texas) where they co-occur (Ford and Oliver 2015, p. 8). DR AF Mussels in the genus Truncilla have miniature glochidia and “use molluscivorous freshwater drum as hosts” (Barnhart et al. 2008, p. 373); that is, freshwater drum are infested with glochidia when they consume female mussels with mature glochidia. Freshwater drum is just one of many fish species known to consume freshwater mussels; other species include: American shad, common carp, black carp, smallmouth buffalo, black buffalo, spotted sucker, river redhorse, striped bass, blue catfish, channel catfish, warmouth, bluegill, red-ear sunfish, and lake sturgeon (McMahon and Bogan 2001, p. 385). Most of these species eat adults of smaller mussel species or juveniles of larger mussel species. However, freshwater drum are specially adapted for feeding on larger mussels with large muscular pharyngeal plates that are capable of crushing shells (McMahon and Bogan 2001, p. 385) and can eat adult mussels, including gravid females. Females of Truncilla species are generally small enough to be eaten by molluscivorus fish like freshwater drum (Haag 2012, p. 178) and this strategy of host infestation may limit population size, as reproductively successful females are sacrificed, explaining sex ratios apparently skewed toward males. While this evolutionary strategy seems likely for Texas fawnsfoot, female selfsacrifice and male-skewed sex ratios have not yet been directly observed in this species. Freshwater drum are benthic generalists and are known to consume various insects, worms, and snails, with larger individuals also consuming crayfish and freshwater mussels (Jacquemin et al. 2014, p. 133). Members of the tribe Lampsilini tend to exhibit long-term brooding (bradytictia), that is, they brood larvae over the winter instead of releasing them immediately (Barnhart et al. 2008, p. 384). 2.B.3. D A GE AND G ROWTH Congeners (Truncilla spp.) from the southeast and the Midwest United States are reported by Haag and Rypel (2010) to reach a maximum age of 8-18 years (Table 1, pp. 4-6) and members of the tribe Lampsilini ranged from 4-50 years (p. 10) with a higher growth rate compared to other tribes (p. 15). No age at maturity information exists for this species (Howells 2010c, p. 3). 2.B.3. E H ABITAT Texas fawnsfoot are found in medium- to large-sized streams and rivers with flowing waters and mud, sand, and gravel substrates (Howells 2014, p. 111), and adults are most often found in bank habitats and Draft Central Texas Mussels SSA Report 17 April 2018 occasionally in backwater, riffle, and point bar habitats with low to moderate velocities that appear to function as flow refuges during high flow events (Randklev et al. 2017c, p. 137). While water quality requirements have not been experimentally determined, observations of temperature and dissolved oxygen inhabited by the species are included in Table 2.4. Table 2.4. Life History and Resource Needs of Texas Fawnsfoot Life Stage Resource Needs Reference  Assumed fish host is freshwater drum. Juveniles -Excystment through sexual maturity  Habitat requirements presumed to be similar to adults. AF Adults     Like other Truncilla species, often found in bank habitats with fine and coarse sediment. Occasionally found in backwater or riffle habitats. Dissolved oxygen greater than approximately 4.8 ppm. Water temperature around 24 degrees C. Dudding et al. 2016, pp.1-3 Howells 2010c, pp. 3-5 DR   Dudding et al. 2016, p.3 T Glochidia through host fish attachment 2.B.4 TEXAS PIMPLEBACK, CYCLONAIAS PETRINA 2.B.4. A T AXONOMIC AND M ORPHOLOGICAL D ESCRIPTIONS The Texas pimpleback was originally described as the species Unio petrinus by A.A. Gould in 1855 from the “Llanos River” in Texas (p. 228). Strecker (1931) recognized the species as Quadrula petrina and noted it as “variable in shape and coloration” and being able to “identify even extreme forms by the plications on the posterior slope of the shell” and included locations from the Colorado River and Onion Creek at Austin (Travis County), Guadalupe River at New Braunfels (Comal County) and in Kendall, Kerr (at Kerrville) Counties, in the Llano River in Llano and Mason Counties, in the San Saba River in Runnels County, the South Concho River in Tom Green County, and the Guadalupe River in Victoria County (pp. 27-8). The Texas pimpleback was recently reassigned from Quadrula to Cyclonaias and the Service recognizes the Texas pimpleback as Cyclonaias petrina in Randklev et al. (2017, p. 280). The following taxonomic treatment follows Williams et al. (2017, pp. 35, 37). Draft Central Texas Mussels SSA Report 18 April 2018 CLASS ORDER FAMILY SUBFAMILY TRIBE GENUS SPECIES Bivalvia Linnaeus, 1758 Unionida Gray, 1854 Unionidae Rafinesque, 1820 Ambleminae Rafinesque, 1820 Quadrulini Cyclonaias Pilsbry in Ortmann and Walker, 1922 Cyclonaias petrina Gould, 1855 (reassigned from Quadrula) DR AF T The Texas pimpleback is a small- to medium-sized (to 103 mm) mussel with a subquadrate to suboval and moderately inflated “yellow to tan, brown to black, occasionally with vague green rays or concentric blotches” (Figure 2.4); for a more detailed description refer to Howells (2014, p. 93). Figure 2.4. Texas pimpleback from the San Saba River, McCulloch County, Texas. (Photo courtesy Gary Pandolfi, USFWS.) Draft Central Texas Mussels SSA Report 19 April 2018 2.B.4. B G ENETIC D IVERSITY In a recent phylogenetic analysis, Randklev et al. (2017c) suggested that the Colorado River and Guadalupe River clades of Cyclonaias petrina may be divergent enough to warrant the recognition of a new species (Cyclonaias howmanni), a Guadalupe River endemic (pp. 282, 290) based on both genetic and morphological characteristics, and provide a haplotype network with significant intraspecific diversity for each clade in the Cyclonaias petrina species complex (p. 294). Regardless of whether or not “taxonomic splitting” is warranted, the two clades represent significant genetic and ecological diversity and contribute to the representation of the Texas pimpleback. For the purpose of this report we consider Texas pimpleback representative in both the Colorado and Guadalupe Rivers; however, we recognize preliminary information suggests that the Guadalupe River populations may represent a potentially new and currently undescribed species (Cyclonaias howmanni) rather than Texas pimpleback (Cyclonaias petrina) (FWS files). T 2.B.4. C R EPRODUCTION AND F ISH H OST I NTERACTIONS AF Host fishes are unknown for the Texas pimpleback but assumed to be catfish (Family Ictaluridae - North American Catfishes; Howells 2014, p. 111). Several species of native catfishes overlap in range with the Texas pimpleback including black bullhead (Ameiurus melas), yellow bullhead (Ameiurus natalis), blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), tadpole madtom (Noturus gyrinus), freckled madtom (Noturus nocturnus), and flathead catfish (Pylodictis olivaris) (Thomas et al. 2007, pp. 93-100). Attachment of Texas pimpleback glochidia was reported on yellow bullhead, flathead catfish, and bluegill but metamorphosis was not observed (Howells 2010, p.108). Other species of “Quadrula” that occur in Texas are known to have multiple fish hosts in the Centrarchidae, Clupeidae, Ictaluridae, Percidae, and Poecilidae fish families (Ford and Oliver 2015, p. 7). DR Members of the Quadrula quadrula species complex, like Texas pimpleback, have miniature glochidia and “use molluscivorous catfish hosts” and mantle magazines that allow “storage of a bolus of glochidia for reflexive release” (Barnhart et al. 2008, pp. 373, 379). Additionally, members of the tribe Quadrulini can produce conglutinates (Barnhart et al. 2008, p. 376) and tend to exhibit short-term brooding (tachytictia), that is, they release glochidia soon after the larvae mature (p. 384). Texas pimpleback is reported to be reproductively active between April and August (Randklev et al. 2017c, p. 110). 2.B.4. D A GE AND G ROWTH Congeners (Quadrula spp.; now Cyclonaias) from the southeast United States are reported by Haag and Rypel (2010) to reach a maximum age of 15-72 years (Table 1) and members of tribe Quadrulini ranged from 15-91 years (p. 10). No age at maturity information exists for this species (Howells 2010c, p. 3). 2.B.4. E H ABITAT Texas pimpleback occurs in medium- to large-sized streams and rivers in flowing waters with “mud, sand, or gravel bottoms, or sometimes in gravel-filled cracks in the bedrock, often at depths less than 2 Draft Central Texas Mussels SSA Report 20 April 2018 m” and are “not known from impoundments” (Howells 2014, p. 93). They are also found in riffle and run mesohabitats with flowing water (Randklev et al. 2017c, p. 110) (Table 2.5). Table 2.5 Life History and Resource Needs of Texas Pimpleback Life Stage Resource Needs Glochidia through host fish attachment Reference  Presence of host fish, presumed to be catfishes. Randklev et al. 2017c, p. 110  Flowing waters, primarily pools, and runs, in streams Randklev et al. 2017c, p. of moderate size with substrates of mud, sand, gravel, 110 Howells 2010b, pp. 3-5 and cobble. Occasionally found in fine sediment deposited in bedrock crevices and fissures.  Not reported or known to occur in impoundments. AF Adults T Juveniles  Habitat requirements presumed to be similar to -Excystment adults. through ~45 mm 2.C SUMMARY DR This report considers four species of Central Texas mussels, false spike, Texas fatmucket, Texas pimpleback, and Texas fawnsfoot, all of which belong to the subfamily Ambleminae of the family Unionidae. These four are among the fifteen mussel species added to the list of Texas state threatened species by the Texas Parks and Wildlife Department in 2009. These four species occur in one or more of the following basins in Texas: Brazos River, Colorado River, Guadalupe River, and Trinity River. Species needs for each of the four Central Texas mussels generally include a suitable substrate, adequate but not scouring flows, high-quality water, a refuge from high and low flow events, access to appropriate host fishes, and appropriate nutrition. Draft Central Texas Mussels SSA Report 21 April 2018 CHAPTER 3 ‐ POPULATION AND SPECIES NEEDS This chapter considers the historical distribution and those parameters which are important in assessing the viability of each of the four Central Texas mussel species. First, historical range and species distribution are discussed. Then, the conceptual needs of the species are considered, including population resiliency, redundancy, and representation to support viability and reduce the likelihood of extinction, for each of the Central Texas mussel species. T For the purposes of this assessment, viability is defined as the ability of the species to sustain populations in the wild over time, which in this case is considered to be 50 years. Fifty years represents up to five mussel generations and reflects the approximate forecasting time horizon for water supply planning and human population projections for the State of Texas. This assessment further considers viability for each species following the species status assessment framework based on “the conservation biology principles of representation, resiliency, and redundancy (the 3Rs) to evaluate the current and future conditions of a species” and described by Smith et al. (2018, p. 7). AF 3.A. HISTORICAL RANGE AND DISTRIBUTION 3.A.1 FALSE SPIKE The false spike is native to the Brazos, Colorado, and Guadalupe drainages in central Texas (Howells 2010, p. 4; Randklev et al. 2017c, p. 12; Figure 3.1). It was, in the past, thought to have historically occurred in the Rio Grande based on fossil and subfossil shells (Howells 2010, p. 4), but those specimens have now been attributed to Sphenonaias taumilapana Conrad 1855 (no common name; Randklev et al. 2017c, p. 12; Graf and Cummings 2007, p. 309). DR In the Brazos River basin, historical records document the occurrence of false spike in the Little River system and the Brazos River. The species has been collected from the Leon River, a tributary of the Little River, in Bell County and Coryell Counties (Strecker 1931 pp. 18-19; Randklev et al. 2017c, p. 12) and from the Lampasas River, another tributary of the Little River (Randklev et al. 2017c, p. 12). In the Brazos River, the species has been collected from the boundary of Brazos and Burleson Counties (Randklev et al. 2017c, p. 12). False spike was once considered common wherever it was found; however, beginning in the early 1970s, the species began to be regarded as rare throughout its range, based on collection information (Strecker 1931, pp. 18-19; Randklev et al. 2017c, p. 13). Williams et al. (1993, p.14) noted that false spike was rare throughout its range and ranked it threatened, and Nature Serve (2016, p.1) ranked the species as critically imperiled. Howells (2010, p. 4) indicated that no living populations were known in the previous 30 years. However, in 2011 the discovery of 7 live false spike in the Guadalupe River, near Gonzales, Texas, was the first report of living individuals in nearly four decades (Randklev et al. 2011, p. 17). Draft Central Texas Mussels SSA Report 22 April 2018 T AF DR Figure 3.1 Presumed historical distribution of false spike in the Brazos, Colorado, and Guadalupe River basins of Texas. Draft Central Texas Mussels SSA Report 23 April 2018 3.A.2 TEXAS FATMUCKET The Texas fatmucket once existed with historical populations in at least 16 rivers in the upper Colorado and Guadalupe basins of the east-central portions of the Edwards Plateau ecoregion, known as the “Hill Country” of Central Texas (Figure 3.2). In the Colorado River, it ranged from Travis County upstream approximately 320 kilometers (km) ((200 miles (mi)) to Runnels County. It was also found in many tributaries including the Pedernales, Llano, San Saba, and Concho Rivers, and Jim Ned, Elm, and Onion Creeks (Howells et al. 1996, p. 61). Howells (2004, p. 7) noted that no live unionids (native freshwater mussels) were reported from Elm Creek or from the Colorado River near Ballinger, Texas, in August 2003. T Strecker (1931, p. 39) described Texas fatmucket as being “especially common in the San Saba and Llano rivers” and attaining high densities in the Concho River and notes locations on Cypress Creek (Blanco County), Guadalupe River in Comal (at New Braunfels), Kendall, Kerr Counties, San Saba River in Menard and McCulloch Counties, Llano River in Mason County, Colorado River in Runnels County, and South Concho River in Tom Green County. AF In the Guadalupe River basin, the Texas fatmucket occupied approximately 240 km (150 mi) of the Guadalupe River, from Gonzales County upstream to Kerr County, including the North Guadalupe River, Johnson Creek, and the Blanco River. Strecker (1931, pp. 66–8) reported Texas fatmucket from a lake in Victoria County in the lower Guadalupe River drainage but this is probably a misidentified Louisiana fatmucket, which is known to occur in lakes and impoundments (Howells 2010c, p. 6). A Salado Creek record from Bell County (Strecker 1931, pp. 62–3) is also probably a misidentified Louisiana fatmucket because Texas fatmucket is not known to occur in the Brazos River basin or its tributaries (Howells et al. 1996, p. 61; Howells 2010c, p. 6). DR In the San Antonio River basin, questionable records exist from the Medina River in Bexar County upstream to the City of San Antonio, as well as in the Medina River and Cibolo Creek (Howells et al. 1996, p. 61; Howells 2010c, p. 6). San Antonio River accounts of Texas fatmucket are most likely misidentified Louisiana fatmucket (Lampsilis hydiana). Given extensive mussel survey efforts in the San Antonio River basin over the last 30 years (San Antonio River Authority 2017, p. 1), it is likely that additional records would exist if Texas fatmucket was present in the San Antonio River or its tributaries (Randklev 2018, entire). Therefore, this report does not consider the Texas fatmucket to have historically occurred in the San Antonio River basin. Draft Central Texas Mussels SSA Report 24 April 2018 T AF DR Figure 3.2 Presumed historical distribution of Texas fatmucket in the Colorado and Guadalupe River basins of Texas. Draft Central Texas Mussels SSA Report 25 April 2018 3.A.3 TEXAS FAWNSFOOT T Strecker (1931, p. 48) noted that the Texas fawnsfoot was abundant in both the Brazos and Colorado Rivers, based on the presence of shell material. The Texas fawnsfoot is endemic to the Brazos and Colorado River basins of central Texas (Howells et al. 1996, p. 143; Randklev et al. 2010a, p. 297; Figure 3.3) and was recently reported from the Trinity River (Randklev et al. 2017b, pp. 9-10). Texas fawnsfoot was presumed to have been extirpated from most of its range until recently (Randklev et al. 2017, p. 137) because malacologists working in central Texas from the 1960s-90s found few individuals in few new locations (Howells 2010d, p. 6). Historical records suggest the Texas fawnsfoot inhabited much of the Colorado River basin, from the mainstem Colorado River in Wharton County upstream to the North Fork of the Concho River in Sterling County, and throughout the Concho, San Saba, Llano Rivers and Onion Creek (Howells 2010d, p. 4; Randklev et al. 2010b, p. 24). In the Brazos River, the species occurred from Fort Bend County upstream to the lower reaches of the Clear Fork of the Brazos River in Shackelford County, as well as in the Leon, Little, Navasota, and San Gabriel Rivers, as well as Deer and Yegua Creeks (Howells 2010d, pp. 4–5; Randklev et al. 2010b, p. 24). DR AF Early reports and accounts of Texas fawnsfoot (Truncilla macrodon) from the Trinity River and other East Texas waters were until recently considered to be misidentified fawnsfoot (Truncilla donaciformis; Howells 2010d, p. 4, Howells 2014, pp. 111-2). However, a recent investigation of the Trinity River mussels (Randklev et al. 2017b, pp. 9-11) suggests that the fawnsfoot collected from the Trinity River may actually be Truncilla macrodon (Texas fawnsfoot) rather than Truncilla donaciformis (fawnsfoot) and that the species still occurs in the East Fork of the Trinity River and in middle sections of the mainstem of the Trinity River, generally near Oakwood, Texas. Preliminary phylogenetic studies appear to support the conclusion that Truncilla macrodon, rather than Truncilla donaciformis, is the species that actually occurs in the Trinity River (Inoue et al. 2018, pp. 4-13). Draft Central Texas Mussels SSA Report 26 April 2018 T AF DR Figure 3.3 Presumed historical distribution of Texas fawnsfoot in the Trinity, Brazos, and Colorado River basins of Texas. Draft Central Texas Mussels SSA Report 27 April 2018 3.A.4 TEXAS PIMPLEBACK The Texas pimpleback is endemic to the Colorado and Guadalupe River basins of central Texas (Howells 2002b, p. 3; Figure 3.4). In the Colorado River basin, Texas pimpleback occurred throughout nearly the entire mainstem, as well as numerous tributaries, including the Concho, North and South Concho, San Saba, Llano, and Pedernales Rivers, and Elm and Onion Creeks (Howells 2010e, p. 5; Randklev et al. 2010c, p. 4; OSUM 2011d, p. 1; Randklev et al. 2017b, p. 109). Historical reports of the species in the Brazos and Trinity River basins are misidentified smooth pimpleback (Cyclonaias houstonensis) and western pimpleback (Cyclonaias mortoni; Randklev et al. 2017b, p. 109). DR AF T Within the Guadalupe River basin, the Texas pimpleback occurred throughout most of the length of the Guadalupe and Blanco Rivers (Horne and McIntosh 1979, p. 122; Howells 2010e, p. 5; OSUM 2011d, p. 1; Randklev et al. 2017c, p. 109). In the Guadalupe River, the species ranged from Comal, Guadalupe, Kendall, Kerr, and Victoria Counties (Randklev et al. 2017b, p. 109). Texas pimpleback historically occurred in the Blanco River (Horne and McIntosh 1979, entire), a major tributary of the San Marcos River (Randklev et al. 2017c, p. 109), and several specimens have been reported (San Antonio River Authority 2017a, p. 1; San Antonio River Authority 2017b, pp. 32-4; TIFP and SARA 2017, pp.42-5) from the San Antonio River basin (Salado, San Antonio, and Medina Rivers) but because those specimens are most likely misidentified golden orb (Cyclonaias aurea) and no recent collections of Texas pimpleback have been made from the San Antonio despite significant effort (Randklev et al. 2017c, p. 109, Randklev 2018, SARA 2017a, p. 1), this report does not consider the San Antonio River basin part of the historical distribution of Texas pimpleback. Draft Central Texas Mussels SSA Report 28 April 2018 T AF DR Figure 3.4 Presumed historical distribution of Texas pimpleback in the Guadalupe and Colorado River basins of Texas. Draft Central Texas Mussels SSA Report 29 April 2018 3.B NEEDS OF CENTRAL TEXAS MUSSELS 3.B.1 POPULATION RESILIENCY T For each of the Central Texas mussel species to maintain viability, its populations or some portion thereof must be resilient. Stochastic events that have the potential to affect Central Texas mussel populations include high flow events that result in scour, mobilization of substrates, and burial of mussel beds (these events include flash floods following heavy rains, bank collapse events, etc.), extended droughts and other dewatering events, pollutant discharge events, large-scale depredation events and disease outbreaks, high water temperature and low dissolved oxygen events, golden algae blooms, and accumulations of large amounts of fine sediment. A number of factors influence the resiliency of populations, including occupied stream length, abundance, and recruitment. Influencing those factors are elements of habitat that determine whether mussel populations can grow to maximize habitat occupancy, thereby increasing the resiliency of populations. These factors and habitat elements are discussed below and in the context of the needs of the individual mussel as presented in Chapter 2 of this report (Tables 2.1-2.5). P OPULATION F ACTORS THAT I NFLUENCE R ESILIENCY DR AF Occupied Stream Length – Most freshwater mussels, including the Central Texas mussel species, are found in aggregations, called mussel beds, that vary in size from about 50 to >5000 square meters (m2), separated by stream reaches in which mussels are absent or rare (Vaughn 2012, p. 2). As discussed above, we define a mussel population at a larger scale than a single mussel bed; it is the collection of mussel beds within a stream reach between which infested host fish may travel, allowing for ebbs and flows in mussel bed density and abundance over time throughout the population’s occupied reach. Therefore, resilient mussel populations must occupy stream reaches long enough such that stochastic events that affect individual mussel beds do not eliminate the entire population. Repopulation by infested fish from other mussel beds within the reach can allow the population to recover from these events. We consider populations extending more than 50 miles to be highly resilient to stochastic events because a single event is unlikely to affect the entire population. Populations occupying reaches between 20 and 49 river miles have some resiliency to stochastic events, and populations occupying reaches less than 20 miles have little resiliency (Table 3.1). Note that, by definition, an extirpated or functionally extirpated population occupies a stream length of approximately (or approaching) 0. Table 3.1 Occupied stream length of healthy, moderately healthy, and unhealthy Central Texas mussel populations. Occupied Stream Length Species All Four Central Texas mussel species Healthy ≥ 50 river miles Draft Central Texas Mussels SSA Report Moderately Healthy 49-20 river miles 30 Unhealthy ≤ 19 river miles April 2018 T Abundance – Mussel abundance in a given stream reach is a product of the number of mussel beds and the density of mussels within those beds. For populations of Central Texas mussel species to be healthy (i.e., resilient), there must be many mussel beds of sufficient density such that local stochastic events do not necessarily eliminate the bed(s), allowing the mussel bed and the overall local population within a stream reach to recover from any one event. We measure mussel abundance by the number of beds within the population, and the estimated density of the species within each bed. Mussel abundance is indicated by the number of individuals found during a sampling event; mussel surveys rarely are a complete census of the population, and instead, density is estimated by the number found during a survey event using various statistical techniques. Because we do not have population estimates for most populations of Central Texas mussels, nor are the techniques directly comparable (i.e., same area size searched, similar search time, etc.), we are using the number of individuals captured as an index over time. While we cannot precisely determine population abundance at the sites using these numbers, we are able to determine if the species is dominant at the site or rare, and examine this over time if that data is available. Table 3.2 displays the densities of healthy, moderately healthy, and unhealthy populations of each species. 3.2 Number of mussels per collection event in a single mussel bed of healthy, moderately healthy, unhealthy population, and functionally extirpated populations of Central Texas mussels. AF  Table Number of individuals per sampling event per site Species Found in nearly all available habitats surveyed. More than 100 individuals found per population survey. Unhealthy Found in approx. Found in few 50% of all areas of suitable available habitats habitat. Between surveyed. Between 2 – 25 26 – 99 individuals individuals found found per per population population survey. survey. DR All Four Central Texas Mussel Species Healthy Moderately Healthy Extirpated/ Functionally Extirpated Very few or no live individuals documented during surveys (≤ 1). Reproduction – Resilient Central Texas mussel populations must also be reproducing and recruiting young individuals into the reproducing population. Population size and abundance reflects previous influences on the population and habitat, while reproduction and recruitment reflect population trends that may be stable, increasing, or decreasing. For example, a large, dense mussel population that contains mostly old individuals is not likely to remain large and dense into the future, as there are few young individuals to sustain the population over time (i.e., death rates exceed birth rates and subsequent recruitment of reproductive adults resulting in negative population growth). Conversely, a population that is less dense but has many young and/or gravid individuals may likely grow to a higher density in the future (i.e., birth rates and subsequent recruitment of reproductive adults exceeds death rates resulting in positive population growth). Detection rates of very young juvenile mussels during routine abundance and distribution surveys are extremely low due to sampling bias because sampling for these species Draft Central Texas Mussels SSA Report 31 April 2018 involves tactile searches and mussels < 35 mm are very difficult to detect (Strayer and Smith 2003, pp. 47-48). Evidence of reproduction is demonstrated by repeated captures of small-sized individuals (near the low end of the detectable range size ~35 mm) over time and by observing gravid (with eggs) females during the reproductively active time of year (Table 3.3). Table 3.3 Evidence of reproduction in healthy, moderately healthy, unhealthy, and functionally extirpated populations of Central Texas mussels. Evidence of Reproduction Species Healthy Moderately Healthy Unhealthy Extirpated/ Functionally Extirpated AF T 50% or more 25-50% of sites < 25% of sites No evidence All Four sites with inhabited by inhabited by juveniles suggesting that Central Texas juveniles (< 35 juveniles (< 35 mm) (< 35 mm) and gravid the juveniles or Mussel mm) and gravid and gravid females females present during gravid females Species females present present during the the breeding season are present. Fish during the breeding season and and fish host present in host not known to breeding season fish hosts present in low abundance and/or occur. and fish hosts moderate abundance. ability to disperse is present. reduced. H ABITAT E LEMENTS THAT I NFLUENCE R ESILIENCY DR Substrate – Suitable substrate types vary between species of freshwater mussels, including the Central Texas mussels. All species need stable substrate in which to anchor. Three of the Central Texas mussels occur primarily in riffle habitats made up of sand and gravel and occasionally in boulder and bedrock crevices. One species is more tolerant of finer substrates in shallow bank habitats and can occasionally is found in riffles (see Chapter 2). The substrate needs of the Central Texas mussel species are displayed in Table 3.4. Draft Central Texas Mussels SSA Report 32 April 2018 Table 3.4 Substrate conditions of healthy, moderately healthy, unhealthy, and functionally extirpated populations of Central Texas mussels. Substrate Conditions Texas fatmucket Riffle and run habitats present. Gravel and cobble substrates sufficient to provide lodging habitat. Low levels of excess sediment in the substrate matrix. Riffle and run habitats eroded, unstable, or being buried by mobilized sediments from upstream sources. No suitable habitat present. Bedrock fissures and crevices present. Substrate sufficient in places to provide anchoring while other areas scoured or too heavily filled with sediment. Fissures and crevices obstructed with excess sediment. Relatively high amount of sedimentation and filling of interstitial spaces. No suitable habitat present. Clay, mud, and sand banks present. Stream banks stable and without documentation of erosion. Clay, mud, and sandbanks present. Stream banks mostly stable with some erosion/scouring. Stream unstable and erosion occurring during high flow. Suitable substrate limited isolated locations. No suitable habitat present. Riffle and crevice habitat present. Gravel and cobble substrate sufficient to provide lodging. Riffle and crevice habitat present. Gravel and cobble substrate sufficient to provide lodging with some sediment deposition. Riffles eroded or upstream sediments deposited at high enough level to precluded inhabitation. No suitable habitat present. Bedrock fissures and/or vegetative crevices present. Substrate sufficient to provide anchoring within crevices but not filled with sediment. DR Texas fawnsfoot Riffle and run habitats present. Gravel and cobble substrates sufficient to provide lodging habitat. Very low evidence of excessive sediment in the substrate matrix. Texas pimpleback Unhealthy Extirpated/ Functionally Extirpated T False spike Healthy AF Species Moderately Healthy Flowing Water – Freshwater mussels need water for survival. Some of the Central Texas mussels are more resilient to low-velocity water than others (e.g. Texas fatmucket can persist in temporary pools during times of drought). Lentic waters (lakes or other non-flowing systems) are not suitable for any of the four species. None of the Central Texas mussel species are found to persist or be tolerant of areas that are regularly dewatered. The flowing water needs of the Central Texas mussel species are displayed in Table 3.5. Draft Central Texas Mussels SSA Report 33 April 2018 Table 3.5 Flowing water conditions of healthy, moderately healthy, unhealthy, and functionally extirpated populations of Central Texas mussels. Flowing Water Unhealthy Flowing water present year-round. Water levels sufficient to keep known habitats constantly submerged. No documented habitat exposure. Flowing water present year-round, but water levels approaching low levels. No instances of zero flow days and riffle dewatering not documented. Flowing water not present year-round. Summer records of zero flow days. However, at least some pools stay sufficiently wetted, cool, and oxygenated. Streambed dry or the number of zero flow days high enough to result in dewatered habitats, precluding survival of mussels. Flowing water present year round. No recorded periods of zero flow days. Water levels sufficient to keep known habitats submerged. Flowing water present almost year round. Few instances of zero flow days or minimal exposure of portions of known habitats. Flowing water doesn’t persist. Summer records of zero flow days while pools stay wetted and sufficiently cool and oxygenated. Dry stream bed or zero flow days high enough to preclude survival. Flowing water present year-round and sufficient to maintain water quality. No recorded periods of zero flow days. No documented of dewatered habitats. Flowing water present year-round, but water levels approaching low levels. No instance of zero flow days and stream bank drying deviates from appropriate hydrology, with limited habitat desiccation. Flowing water doesn’t persist annually. Stream banks documented to dry during low flow. Habitat desiccation occurs. Dry stream bed or zero flow days high enough to preclude survival. Flowing water present year-round and sufficient to maintain temperature and dissolved oxygen. No recorded periods of zero flow days. No documented habitat exposure. Flowing water present year-round, but water levels approaching low levels. No instances of zero flow days and riffle dewatering not documented. Zero flow days or riffle dewatering documented within previous decade. Dry stream bed or zero flow days high enough to preclude survival. DR Texas fatmucket Moderately Healthy T False spike Healthy AF Species Texas fawnsfoot Texas pimpleback Extirpated/ Functionally Extirpated Draft Central Texas Mussels SSA Report 34 April 2018 Water Quality – Freshwater mussels, as a group, are very sensitive to changes in water quality parameters such as dissolved oxygen, salinity, ammonia, and pollutants (Chapter 6). Habitats with appropriate levels of these parameters are considered suitable, while those habitats with levels outside of the appropriate ranges are considered less than suitable. The water quality needs of Central Texas mussels are displayed in Table 3.6. Table 3.6 Water quality conditions of healthy, moderately healthy, unhealthy, and functionally extirpated populations of Central Texas mussels. Water Quality Healthy Contaminants known, low dissolved oxygen and temperature extremes documented. Levels not high enough to risk extirpation. Known exposure to contaminants, low dissolved oxygen, and documented cases of excessive water temperatures extremes. Water quality parameters diminished such that exposure threatens mussel survival. AF No known incidence of contaminant spills, low dissolved oxygen, or evidence of exposure extreme high or low temperatures Unhealthy Water quality degradation such that occupancy of otherwise suitable habitat is precluded DR All four Central Texas mussel species Extirpated/ Functionally Extirpated T Species Moderately Healthy       Draft Central Texas Mussels SSA Report 35 April 2018 CHAPTER 4 ‐ RIVER BASINS AND SECTIONS OF INTEREST 4.A. MAJOR CENTRAL TEXAS WATERSHEDS ‐ GENERAL CURRENT CONDITIONS AF T Texas has over 191,000 miles of rivers and streams, seven major estuaries, over one thousand public water bodies, and approximately 200 major streams, all of which provide important services to nearly 270 species of freshwater fish, resident and migratory wildlife, plants, and to over 25 million people throughout the State of Texas (Loeffler 2015, p.1). Texas has only one natural lake, Caddo Lake, in the Cypress Creek Basin of East Texas, which is believed to have been formed by an ancient logjam known as the “Great Raft of the Red River” more than two hundred years ago; that logjam was removed by 1873 and a dam was completed in 1914 (Winemiller et al. 2005, pp. 1-5). Over one hundred (138) major reservoirs had been constructed on Texas rivers before 1960 (Dowell 1964, pp.3-8) and Texas now has 188 major reservoirs and numerous river diversions (TWDB 2017, p. 62). The construction of new reservoirs has slowed, partly because few viable sites remain for major reservoirs, environmental permitting, and construction costs (TWDB 2018d, p. 1). That said, 26 new major reservoirs have been recommended, along with additional strategies, by the regional water planning groups to provide additional surface water supplies (TWDB 2017, p.87), and additional strategies to enhance water supply in the State include: demand management (water conservation), reuse (of treated wastewater), groundwater development (and aquifer storage and recovery), and seawater (desalination; TWDB 2017, p. 90). Many of the proposed new reservoirs are off-channel reservoirs (OCR) that will not be built on the main stem of the rivers but may rely on flows from the main stem, through pumping, or “scalping” during high flow events (TWDB 2017, p. 95). According to the 2017 State Water Plan, prepared by the Texas Water Development Board (2017, p. 30): DR The human population of the State of Texas is expected to increase more than 70% over the next fifty (50) years, from 2020 to 2070, from 29.5 million to 51 million. During that same time, water demands are projected to increase by 17%, from 18.4 million to 21.6 million acre-feet per year. Existing water supplies in the State of Texas is expected to decline from 15.2 million to 13.6 million acre-feet per year, representing an 11% decrease, and water user groups face a potential water shortage of 4.8 million acre-feet per year in 2020 and 8.9 million acre-feet per year in 2070, assuming drought of record conditions. Texas is one of six states in the United States to have a mixed water law between riparian rights and prior appropriation. Only permitted surface water rights in Texas are subject to prior appropriation. Texas permitted surface water rights are regulated using a “first-in-line, first-in-time” priority framework by the Texas Commission on Environmental Quality, the state’s environmental agency (30 Texas Administrative Code 297.21). River Authorities are quasi-governmental agencies or divisions of the State of Texas, with boards usually being appointed by the Governor. Seventeen river authorities and numerous other special law districts have been established to manage and allocate surface water resources throughout the state (TWDB 2014, p. 1). Groundwater, on the other hand, is regulated more loosely by the rule of the “right of capture” as groundwater rights are tied to surface rights (Sansom 2008, p. 6) and are managed more locally, generally Draft Central Texas Mussels SSA Report 36 April 2018 at the scale of one or more counties. Ninety-eight Groundwater Conservation Districts (GCDs) have been created across Texas and can be given authority to regulate the spacing and production of water wells (TWDB 2018a, p. 1). Groundwater is important to freshwater mussels, given that spring flows and other groundwater inputs contribute substantially to base flows in many Central Texas rivers (Wolaver et al. 2014, p. 15). AF T Given the continental climate and influence of the Gulf of Mexico, Central Texas climate is characterized by prolonged droughts punctuated by major rainfall events leading to significant runoff and flooding. Evaporative demand is high. For example, in southern Central Texas, potential evapotranspiration (ET) can range from 75% (during relatively wet years) to 121% (during very dry years) of available rainfall on an annual basis, such that residual soil moisture from a previous year can be depleted during a subsequent dry year (USGS 2010, pp. 34-5). Central Texas is considered by many as “Flash Flood Alley” because of a combination of factors including landforms and the frequency and severity of rainfall intensities that are commonly experienced throughout the region (TWRI 2016, pp. 6-10). Notable events include: the 2015 Memorial Day storms; 1978 flooding of the Guadalupe River at Comfort, Texas associated with Hurricane Amelia; and most recently flooding associated with Hurricane Harvey in August, 2017. Given the widespread scale and extent of flooding and impacts to human lives and property in Texas, the Texas Water Development Board (TWDB) is currently developing a statewide flood plan (Texas Tribute 2017, p. 2). Furthermore, drought and flood events in Texas tend to follow each other, and historically many Texas droughts have been broken by intense rainfall leading to flooding (TWRI 2016, p. 3). WATER AND ENVIRONMENTAL FLOWS IN TEXAS DR The 77th Texas Legislature passed Senate Bill 2 (SB2) in 2001 and established the Texas Instream Flow Program (TIFP) to “perform scientific studies to determine flow conditions necessary to support a sound ecological environment in the rivers and streams of Texas” (TIFP-BRA 2010, p. 5). The Texas Instream Flow Program has provided funding for multiple studies on various aspects of “how water flow affects river characteristics including aquatic life and habitat, water quality, movement of nutrients and organisms, stream channel formation, and relationships between rivers and surrounding habitat” (TWDB 2018b, p. 1). The 80th Texas Legislature passed Senate Bill 3 (SB3) in 2007 to establish a “comprehensive, statewide process to protect environmental flows” and represents a collaboration between Texas Parks and Wildlife Department (TPWD), Texas Commission on Environmental Quality (TCEQ), and Texas Water Development Board (TWDB), and others. This legislation instructed TCEQ to establish minimum environmental flows criteria for those basins with water available to be appropriated in the future (Loeffler, 2015 entire). Environmental Flow Regime Recommendations Reports were provided to TCEQ by the Basin and Bay Expert Science Team (BBEST) for each major basin described in this report. The Hydrology-based Environmental Flow Regime (HEFR; Opdyke et al. 2014, entire) tool was developed during the SB3 process and describes flow regimes in terms of subsistence flows, base flows, pulse flows, and overbank floods and applies the Indicators of Hydrologic Assessment (IHA; TNC 2009, entire) to determine hydrologic separation and then inform an environmental flow recommendation. Environmental Flow Standards (TCEQ 2011a, entire) exist for each of the major river basins considered in this report, the Brazos (TCEQ 2011b, entire), Colorado (TCEQ 2011c, entire), Guadalupe (TCEQ 2011d, entire), and Draft Central Texas Mussels SSA Report 37 April 2018 Trinity (TCEQ 2011e, entire). Each of these major river basins was found to be “healthy and sound ecological environments” and minimum flow recommendations were made in Environmental Flows Recommendations Reports, by the Basin and Bay Expert Science Team (BBEST) for each basin. A Water Availability Model (WAM) “simulates how much water is available under different or alternative management scenarios through a repeated period of hydrology...[and uses] historic streamflow and evaporation data to calculate the supply of available surface water” (LCRA 2014a, p. ES-6). Usually, a WAM is used to develop firm yield and interruptible storage based on the Drought of Record under alternative scenarios of water use. In such cases, Firm Water rights are protected over Interruptible Stored Water (LCRA 2014a, p. ES-7). WAMs are used by TCEQ and others to evaluate water rights permit applications and by TWDB for regional water planning (LCRA 2014b, p. 12). DR AF T This section of the report considers, by basin, river and stream segments that, based on the best available information, are believed to be currently occupied by one or more of the Central Texas mussel species (Figure 4.1). Note that each of the four species occupies different ecological niches and has habitat preferences and sensitivities, and thus, may occupy different portions of the river and stream segments described below. Draft Central Texas Mussels SSA Report 38 April 2018 T AF DR Figure 4.1. Map of the Brazos, Colorado, Guadalupe, and Trinity River Basins of Central Texas. Draft Central Texas Mussels SSA Report 39 April 2018 4.B BRAZOS RIVER AND BASIN The Brazos River originates in the Texas High Plains and terminates directly into the Gulf of Mexico near Freeport, Texas (Sansom 2008, pp. 50, 91). The total length of the Brazos River is 840 miles (TWDB 2018b, p.1). Important tributaries include the Bosque, Leon, Little, and Navasota Rivers, and Yegua Creek. Major cities along the Brazos River include Waco and Bryan-College Station. DR AF T The Brazos River Authority (BRA) was created by the Texas Legislature in 1929 to develop, manage and protect the surface water resources of the Brazos River basin (BRA 2018a, p. 1). The first major dam, which created the Possum Kingdom reservoir, was constructed in the upper watershed in 1941 (TISPBRA 2010, p. 5). There are now 27 major reservoirs in the Brazos River basin [16 have > 50,000 acrefeet of storage, (BBEST 2012, p. 33], three of which are owned and operated by the BRA: Possum Kingdom (on the Brazos), Granbury (completed on the Brazos in 1969), and Limestone (completed on the Navasota in 1978). The U.S. Army Corps of Engineers (USACE) operates dams on Lake Whitney (hydropower) on the Brazos River, Lakes Proctor and Belton on the Leon River, Stillhouse Hollow on the Lampasas River, Lakes Georgetown and Granger on the San Gabriel River, Lake Somerville on Yegua Creek, and Aquilla on Aquilla Creek (BRA 2014, pp. 4-5). The Allens Creek Reservoir is proposed for construction as an off-channel reservoir to the Brazos, on Allens Creek near the City of Wallis, to provide water supply and storage for the City of Houston (BRA 2018, p. 1). Water is planned to be pumped from the Brazos River during high flows will be stored and released back into the river to meet downstream needs during periods of low flow. The BRA “Systems Operation Permit” allows BRA to “use the bed and banks of the Brazos River and its tributaries to deliver stored water [from BRA reservoirs] to downstream customers.” The BRA Water Management Plan and System Operations Permit prohibit diversions and water storage when “instantaneous flow values at the reach measurement point are below the applicable base and subsistence flow conditions” (BRA 2014, p. 29). The BRA manages firm supplies, which are considered to be “the reliable supply of water available from the BRA system given existing or expected authorizations” as well as non-firm, or interruptible, supply that becomes available when “special conditions of the System Operation Permit are met” (BRA 2014, pp. 52-3). There are no major dams on the Brazos River below Waco; Lake Whitney (2,000,000 acre-feet, completed in 1951) is the most downriver on-channel reservoir on the Brazos, and in the Lower Brazos flows become more influenced by seasonal precipitation patterns in the basin. Known mussel populations have been identified in this approximately 300-mile long lower section of the Brazos River, generally downstream of the City of Waco to near Brazoria, Texas. Freeport, Texas, is the site of the Dow Chemical plant, which came into operation in 1941 to extract magnesium from seawater to support the World War II effort (Dow Texas Operations 2018, entire). Dow Chemical is the largest water user on the Brazos, and holds the oldest water rights in the basin (Sansom 2008, pp. 91-3). The Brazos Basin provides an important surface water supply for the Region G (57% of existing water supply) and Region H (19% of existing water supply) Regional Water Planning Regions of Texas Draft Central Texas Mussels SSA Report 40 April 2018 (TWDB 2016, pp. G-4, H-4). Region G includes the major cities of Abilene, Bryan, College Station, Killeen, Round Rock, Temple, and Waco. Region H includes the Houston metropolitan area. T Dow Chemical Company has the most senior water rights in the Brazos, established in 1942. Near the end of the 2011-12 drought, the Dow Chemical Company made a “priority call” to TCEQ, which then suspended withdrawals by junior rights on the Brazos. When TCEQ suspended these junior rights, certain municipal water and hydropower rights were “excepted” under the “Drought Rules” (30 Texas Administrative Code 36.3). Of the 845 suspended water rights, 716 were for irrigation of agricultural products (AgriLife 2015, p. 1). Texas Farm Bureau challenged the Drought Rules and filed suit on behalf of several irrigations, arguing that TCEQ violated the Texas Water Code by suspending some of the junior rights, but not others. The court sided against TCEQ, declaring the Drought Rules invalid, and the ruling stood upon appeal (TCEQ v. Texas Farm Bureau, 2015, pp. 14-15). Thus, the doctrine of prior appropriation, “first in time, first in right” was upheld and can be expected to continue to do so in the future, such that senior water rights, often near the coast, are upheld over more junior rights during drought conditions. In this case, the more junior rights are located upstream from the senior rights. AF A watermaster was established for the Brazos River (Possum Kingdom Lake and below) by TCEQ in 2014 and has responsibilities which include: allocating water by right, monitoring stream flows and water use, and responding to complaints and enforcing compliance, and “when streamflows diminish, the watermaster will allocate available water among the water right holders according to each user’s priority date” (TCEQ 2018a, p. 1). This report considers four river sections in the Brazos Basin known to support populations of one or more species of Central Texas mussels. DR 4.B.1 LOWER CLEAR FORK OF THE BRAZOS RIVER This segment of the Clear Fork of the Brazos River is generally in Throckmorton, Shackelford, Stephens and Young Counties, Texas, and includes portions of TCEQ-classified segments 1207 (Possum Kingdom Lake) and 1208 (Brazos River above Possum Kingdom Lake). As recommended by the 2016 Brazos G Regional Water Plan (TWDB 2016, p. G5), the City of Abilene is “actively pursuing the necessary permits and engineering required” to build the Cedar Ridge Reservoir in Shackelford County on the Clear Fork of the Brazos, which would inundate up to 8,786 acres of land north of Abilene, Texas (HDR 2016, p. 1). The U.S. Army Corps of Engineers is preparing an Environmental Impact Statement in support of this water supply project (USACE 2018, entire). 4.B.2 UPPER BRAZOS RIVER This segment of the Upper Brazos River is generally from Possum Kingdom Reservoir downstream to Lake Granbury and includes TCEQ segment 1206 (Brazos River below Possum Kingdom Lake), and USGS gage 08089000 near Palo Pinto, Texas. This segment is reported to have a fish assemblage of low biotic integrity, dominated by generalists, and with notable declines in abundance of fluvial specialists, associated with flow alterations (BBEST 2012, pp. 1-4, 4-7, referred to as the Middle Brazos River). Draft Central Texas Mussels SSA Report 41 April 2018 Flows at the USGS gage 08089000 were low (below 100 cubic feet per second (cfs)) from November 2009 to January 2010, and in 2011 the flow conditions in the Brazos River were so low that Dow’s Freeport operations were impacted and some portions of the river ran dry (Reddy et al. 2015, p. 96). Flows in this segment are dominated by releases from the Morris Sheppard Dam which was completed on the Brazos River in 1941 (Dowell 1964, p. 5), with a hydroelectric generating facility that is no longer in use (BRA 2018d, p.1). 4.B.3 LITTLE RIVER This occupied segment of the Little River is generally between Holland and Buckholts in Williamson and Milam Counties, Texas, and includes portions of TCEQ-classified segment 1213 (Little River). T The Little River is 75 miles long from the confluence of the Leon and Lampasas Rivers in Bell County to the Brazos River in Milam County, Texas (Handbook of Texas online 2018b, p. 1). The San Gabriel River is an important tributary, upon which Granger Lake was completed in 1972, and has been impounded since 1980 (HDR 2016b, p.1). AF Brushy Creek Regional Wastewater Treatment Plant is operated by the cities of Round Rock, Cedar Park, and Austin, Texas, and discharges into Brushy Creek in Round Rock. DR The Little River Off-Channel Reservoir (OCR) is proposed as a 4,343-acre impoundment on Pin Oak Creek, a tributary to the Little River, near Cameron in Milam County, Texas. This project contemplates an intake structure for diverting water from either the Little River, or from the main stem of the Brazos River (HDR 2016c, p. 1), and modeled streamflow reductions are reported to be “minimal” to downstream rights (HDR 2016c, p. 2) but negative impacts are likely at the proposed reservoir site and immediately downstream associated with the construction and operation of the project (HDR 2016c, p. 11). Note that the proposed reservoir is not located at a site currently known to support Central Texas mussels, and downstream impacts in the Little River or Brazos River are considered minimal, and if permitted, the Little River OCR would likely be subject to environmental flow requirements (HDR 2016c, p. 10). 4.B.4 MIDDLE/LOWER BRAZOS RIVER This segment of the Brazos River is generally downstream of the confluence with Yegua Creek in Burleson County, Texas, and Rosharon in Fort Bend County, Texas, and includes portions of TCEQclassified segments 1242 (Brazos River above Navasota River), 1202 (Brazos River below Navasota River), and 1245 (Upper Oyster Creek). Construction of Lake Somerville on Yegua Creek began in 1962 (Dowell 1964, p.8). Construction of Lake Limestone, a water supply reservoir on the Navasota River was completed in 1978 (BRA 2018c, p.1). The proposed new Allens Creek Reservoir is proposed to divert (pump) water from the Brazos River for storage and later use. Allens Creek itself was found not to have any Texas fawnsfoot, but a section of the Brazos River known as the 4-mile loop, and below, was found to have a “diverse and abundant mussel Draft Central Texas Mussels SSA Report 42 April 2018 fauna” including Texas fawnsfoot (Randklev et al. 2014, pp.10-11). The 4-mile loop is located immediately downstream of the confluence with Allens Creek (BRA 2018b, p.1), is in close proximity to the proposed reservoir construction site on Allens Creek (TPWD 1994, p.3), such that downstream effects to Texas fawnsfoot and their habitat are likely during and after reservoir construction. AF T The Texas Instream Flow Program and Brazos River Authority described the “Middle and Lower Brazos Basin” as including the Brazos downstream of Lake Brazos in Waco, and the Navasota, Leon, and Little Rivers, and Yegua Creek (TIFP-BRA 2010, pp. 6-7). Historically, the Lower Brazos basin was an extensive floodplain forest system with a complex diversity of interconnected oxbows, wetlands, and other habitats, and today is mostly hydrologically intact and represents one of North America’s largest relatively intact floodplain systems (TIFP-BRA 2010, p. 5) despite the fact that much of the current and recent past land use is agricultural, for row-crops and livestock grazing, and much of the floodplain riparian vegetation has been cleared to near the banks, to the detriment of water quality and aquatic habitats in the basin (TIFP-BRA 2010, p.31). Water quality is reported to be improving, but nutrients remain a concern, due to a variety of sources including wastewater outfalls and runoff (TIFP-BRA, 2010 p. 32). Observations of channel incision at the Brazos River at Seymour (in the upper basin, USGS gage 08082500, Baylor County) and Richmond (in the lower basin, USGS gage 0811400, Fort Bend County) suggest that “the rate of channel migration has slowed substantially in the lower Brazos, indicate that the Brazos River has been undergoing long-term adjustments in response to multiple changes in the river basin that have occurred since the early 1990s and has not yet reached a state of dynamic equilibrium” (BBEST 2012, pp. 7-13). Channel alterations associated with altered hydrology can degrade benthic aquatic habitats. DR 4.C COLORADO RIVER AND BASIN The Colorado River also originates in the Texas High Plains and is the longest river with a drainage basin within the State of Texas and flows into the Gulf of Mexico at Matagorda Bay (Sansom 2008, pp. 50, 94). The total length of the Colorado River is 865 miles (TWDB 2018d, p. 1). Ninety percent (90%) of the Colorado Basin drainage is above the City of Austin (Sansom 2008, p. 93) and flows through the Highland Lakes (see discussion below). Important tributaries to the Colorado include the Concho, San Saba, Llano, and Pedernales Rivers, which are sometimes called the “Hill Country Rivers.” O.H. Ivie Reservoir, on the “Upper” Colorado River, just below the confluence with the Concho River, was completed in 1990 and is owned and operated by the Colorado River Municipal Water District (CRMWD) for water supply and recreational purposes (TWDBd 2018, p. 1). CRMWD also operates the J.B. Thomas and E.V. Spence Reservoirs on the Colorado River above O.H. Ivie (CRMWD 2018, p. 1), and participates in Region F Water Planning. The Colorado Basin provides an important surface water supply for the Region K (Lower Colorado; 71% of existing supply) Regional Water Planning Region of Texas and also provides 8% of the existing water supply for Region F (TWDB 2016, pp. F-4, K-4.) Region K includes the major cities of Austin, Bay City, Pflugerville, and Fredericksburg, Texas. Draft Central Texas Mussels SSA Report 43 April 2018 The Upper Colorado River Authority (UCRA) was created in 1935 to “protect the watershed of Tom Green, Coke, and other contiguous counties” (UCRA 2018, p. 1). The UCRA has been involved in several water quality enhancement projects throughout their service area in Coke, Concho, Crockett, Glasscock, Irion, Menard, Mitchell, Nolan, Reagan, Runnels, Schleicher, Sterling, Taylor, and Tom Green counties (UCRA 2018, p.1). T The Lower Colorado River Authority (LCRA) manages the Lower Colorado River and was created by the Texas Legislature in 1934 for the purposes of flood control, water supply, and rural electrification (LCRA 2018a, pp. 1-2). A series of six “Highland Lake Dams” were built on the lower Colorado River in Central Texas between 1890 and 1942, including the Buchanan Dam on Lake Buchanan, Inks Dam on Inks Lake, Wirtz Dam on Lake LBJ, Starcke Dam on Lake Marble Falls, Mansfield Dam on Lake Travis, and the Tom Miller Dam on Lake Austin. This series of dams are operated by the LCRA to provide hydroelectricity, flood management, and water supply to over 1 million residents of the Austin metropolitan area, and for industrial and agricultural purposes in the lower Colorado River basin (LCRA 2018b, p.1). Special conditions have been incorporated into the water rights permits of the LCRAmanaged Highland Lakes such that instream flows and freshwater inputs are maintained in the Lower Colorado River and to the Matagorda Bay estuary system (Loeffler 2015, p.3). DR AF LCRA manages Lake Buchanan and Lake Travis (the only two of the Highland Lakes with storage) according to a Water Management Plan (WMP) that is subject to review and approval by TCEQ to deliver both “firm” and “interruptible” water demands as well as environmental flow needs for the Lower Colorado River (LCRA 2014a, p. ES-1). LCRA provides water for agricultural irrigation in the lower basin through its four irrigation operations Garwood, Lakeside, Gulf Coast, and Pierce Ranch (LCRA 2014a, p. ES-6), primarily for rice farming and represents, on average, 70% of LCRA’s total annual water use (LCRA 2014a, p. 2-4). Irrigation operations were curtailed due to drought conditions in 2012 and 2013 (LCRA 2014a, p. 2-5). Firm water can be delivered during “worst case” drought conditions (referenced to the Drought of Record) and represents senior downstream water rights (LCRA 2014a, p. ES-4). Interruptible stored water is stored in Lakes Buchanan and Travis and can be “cut off” or “curtailed” during droughts or other shortages, and is used almost entirely to support agricultural irrigation operations, but also supports environmental flow needs in the lower basin (LCRA 2014a, p. ES4). LCRA can release stored water from Buchanan and Travis Reservoirs to supplement “run-of-river” water supplies to help meet additional agricultural irrigation demands during drought conditions, and to support environmental flows in the lower basin (LCRA 2014a, p. ES-7). The LCRA WMP establishes a minimum combined storage for Buchanan and Travis at 600,000 acre-feet as a trigger point for protecting firm water rights during a “Drought Worse than Drought of Record” (LCRA 2014a, p. ES-7) and commits 33,440 acre-feet per year of firm water for environmental flow purposes (LCRA 2014a, p ES-8). LCRA also provides firm water as back up to maintain the cooling reservoir for the South Texas Project Nuclear Operating Company (STPNOC; LCRA 2014a, p. 1-7; LCRA 2014b, p. 47) and to the City of Austin Water Utility and other municipalities (LCRA 2014a, p. 2-3). Environmental flows are informed by a 2008 instream flow study that investigated aquatic habitats and subsistence flow recommendations designed to support February-March spawning of the state-threatened blue sucker near Columbus (Cycleptus elongatus; LCRA 2014a, p. 2-6). LCRA generates hydropower at each of the Highland Lake dams, but only when water is released for other purposes, and those releases are planned to maximize generation potential (LCRA 2014a, p. 2-9). Thus, LCRA has some capacity to implement management actions to ameliorate the effects of droughts on flows in the lower sections of the Colorado River. Draft Central Texas Mussels SSA Report 44 April 2018 There are no major dams on the Colorado River below Austin, save a saltwater barrier weir dam at Bay City, and an off-channel reservoir under construction at Garwood that is intended to as a “scalping” reservoir to supply irrigation needs downriver during drought. There are a total of 31 major reservoirs in the Colorado River basin, including the Highland Lakes (TWDB 2018d, p. 1). LCRA is constructing new off-channel reservoirs in lower sections of the Colorado River including the Arbuckle Reservoir at Lane City in Wharton County and the Prairie Conservation Reservoir near Eagle Lake in Colorado County (LCRA 2018c, p. 1). These new dams and construction projects are not expected to adversely affect flows or water levels downstream once constructed, provided they are managed to “scalp” water during high flow events and store it for later use during drought. However, the construction of these dams, and operation of pumps to fill the reservoirs, could disturb the substrate if mussel habitats are present near the impoundments and intake facilities. AF T According to the LCRA WMP, the primary water quality threats in the Highland Lakes and Lower Colorado River are: nonpoint source pollution (pollutants and contaminants from stormwater runoff), point source pollution (discharges from industry and wastewater treatment plants), soil erosion, reservoir sedimentation, and reduced dissolved oxygen (LCRA 2014a, pp. 1-6). To address these concerns, LCRA is an active participant in the Colorado River Watch Network and the Texas Clean Rivers Program (LCRA 2014a, pp.1-6). Each of the other river authorities mentioned in this report similarly participates in the Texas Clean Rivers program. This report considers eight river segments in the Colorado Basin known to support populations of one or more species of Central Texas Mussels. 4.C.1 LOWER ELM CREEK DR This segment of Elm Creek is generally near Ballinger, in Runnels County, Texas, and is not included in a TCEQ-classified segment, but drains to 1426 (Colorado River below E.V. Spence Reservoir). This small watershed is dominated by agricultural land uses and is relatively small and otherwise intact. In Elm Creek at Ballinger (USGS gage 08127000, annual average daily flows range from <10 to >120 cfs between 1983 and 2008 (BBEST 2011, p. 2-36). Elm Creek at Ballinger is reported to have a number of small springs and seeps and that “much of the creek is reservoir-like with short riffles over bedrock downstream of the dams at low flows” (BBEST 2011, p. 2-38). 4.C.2 LOWER CONCHO RIVER This segment of the Concho River is generally near Paint Rock, in Concho County, Texas, and includes portions of TCEQ-classified segment 1421 (Concho River) and 1433 (O.H. Ivie Reservoir). This segment is downstream from three impoundments, Lake Nasworthy, O.C. Fisher Lake, and Twin Buttes Reservoir. These three reservoirs provide a public water supply for the area and regulate both low and high streamflow. The construction of these dams, together with persistent drought and a lack of water available for controlled releases, has resulted in reduced flood peaks and a “downward” trend in stream discharge (USGS 2012, pp.6-8, Figure 6, pp.13-15). The confluence of the Concho and Colorado rivers is now inundated by O.H. Ivie Reservoir (BBEST 2011, p. 2-46). The Concho River at Paint Rock (USGS gage 08136500) has experienced substantial declines in annual average daily flows since 1931 Draft Central Texas Mussels SSA Report 45 April 2018 (BBEST 2011, p. 2-47) and 8% of days from 1916 to 2010 exhibited no flow (BBEST 2011, p. 2-55). The Concho River at Paint Rock has naturally occurring elevated nitrate and chloride levels (BBEST 2011, p. 2-54). A watermaster was established for the Concho River by TCEQ in 2005 and has responsibilities which include: allocating water by right, monitoring stream flows and water use, responding to complaints and enforcing compliance, and “when streamflows diminish, the watermaster will allocate available water among the water right holders according to each user’s priority date” (TCEQ 2018b, p.1). 4.C.3 UPPER/MIDDLE SAN SABA RIVER DR AF T This segment of the San Saba River is generally in Menard, Mason, and McCulloch Counties, Texas, and includes portions of TCEQ-classified segment 1416 (San Saba River). Most of the flows in the Upper San Saba River (in Menard County, Texas) are from Edwards Formation springs, where it may be considered a “gaining stream” except for, and due to a change in the underlying geology, a “losing reach” near the Menard/Mason County line (LBG-Guyton 2002, p.3, Figure 1). As such, the “upper” (above Menard) and “middle” (below Menard) reaches of the San Saba River in Menard County are considered separately from the “lower” (in McCulloch County) reaches of the San Saba River, of which flows are mostly contributed by Brady Creek, as well as by local precipitation. It is in this “losing reach” where drought effects are especially noticeable, as some flows may percolate downward. The Menard County Underground Water District is the primary groundwater district in Menard County and has some authority for regulating groundwater withdrawals (MCUWD 2012, p. 1). The Menard Irrigation Company maintains approximately 9.7 miles of open ditch canal (the Noyes Canal, Menard Irrigation Canal; USGS 1953, p. 1), that bypasses the San Saba River, approx. 5 miles west and approx. 5 miles east of Menard, Texas. The canal was completed in 1876 and has been operated by the Menard Irrigation Company since 1905. Much of the “middle” San Saba River below Menard is reported to have gone “dry for 10 of the last 16 years” by landowners downstream of Menard (Carollo 2015, p. 2). Regardless of the cause, low flows in the San Saba River have resulted in significant stream drying and stranded Central Texas mussels have been identified following dewatering as recently as 2015 near and below the “losing reach” (TPWD 2015, p. 3). 4.C.4 LOWER SAN SABA RIVER (AND MIDDLE COLORADO RIVER) This segment of the San Saba River is generally between the confluence with Brady Creek and the confluence with the Colorado River in San Saba, County, Texas and includes portions of TCEQclassified segment 1416 (San Saba River). The San Saba River is hydraulically/hydrologically connected to the Colorado River, as there is no major dam at the confluence of the two rivers. Thus, this segment also includes the Colorado River between Pecan Bayou and Lake Buchanan in San Saba, Mills, and Lampasas Counties, Texas, and includes portions of TCEQ-classified segment 1409 (Colorado River above Lake Buchanan) and 1410 (Colorado River below O.H. Ivie Reservoir). Some of the flow in the Lower San Saba River is derived from Brady Creek, which receives wastewater inputs from the City of Brady, Texas. The 1 million gallon per day wastewater treatment plant was Draft Central Texas Mussels SSA Report 46 April 2018 constructed in 1963 and is expected to be replaced, due to obsolescence (TWDB 2015, p. 6; City of Brady 2017, pp. ii-iii). The Lower San Saba River (San Saba River at San Saba, USGS gage 08146000) is reported to flow 99.6% of the time, with groundwater contributing most of the streamflow (Wolaver et al. 2014, p. 9). In, the San Saba River at San Saba, the Edward-Trinity Aquifer is the source of springs and baseflow and annual average daily flows range from <100 to >400 cfs (BBEST 2011, p. 2-79). 4.C.5 LLANO RIVER   T In the Colorado River near San Saba (USGS gage 08147000), annual average daily flows have declined from 1923 to 1990 (BBEST 2011, p. 2-25). For this control point, it has been determined that the existing channel currently appears to be stable, but reductions in the magnitude and frequency of flows could result in major instability in the future, leading to channel incision and bank collapses (BBEST 2011, p. 3-128). AF This segment of the Llano River includes the South Llano River, and is generally in Kimble, Mason, and Llano Counties, Texas, and includes portions of TCEQ-classified segment 1415 (Llano River). The Llano River is largely spring fed (BBEST 2011, p. 2-88). Some conservation is underway in the Llano River Basin, including efforts of the Llano River Watershed Alliance, the Upper Llano River Watershed Protection Plan, and voluntary habitat restoration on private lands coordinated through the Landowner Incentive Program and similar efforts by state and federal biologists, and NGOs (Broad et al. 2016, pp. 53-70). DR Segments of the North Llano River, near Junction, experienced very low flows during drought conditions from May to October 2011 (USGS 2013, p.18), and daily mean stream flows in the Llano River, near Junction, were below 10 cfs in July-August, 2011 (USGS 2013, p.19). In the Llano River at Llano (just below the Llano City Lake, USGS gage 05151500), annual daily average flows ranged from <100 to >1000 cfs from 1940 to 2010 (BBEST 2011, p. 2-89). 4.C.6 PEDERNALES RIVER This segment of the Pedernales River is generally from near Fredericksburg to near Hye in Gillespie and Blanco, Counties, Texas, and includes portions of TCEQ-classified segment 1414 (Pedernales River). Some conservation is underway in the Pedernales River Basin, including voluntary habitat restoration on private lands coordinated through the Landowner Incentive Program and similar efforts by state and federal biologists, and NGOs (TPWD 2018b, p. 2). 4.C.7 LOWER ONION CREEK This segment of Onion Creek is generally from U.S. Highway 183 to the confluence with the Colorado River, near Del Valle in Travis County, Texas, and includes portions of TCEQ-classified segment 1427 (Onion Creek). The Onion Creek near Driftwood (upstream from this segment, USGS gage 08158700) Draft Central Texas Mussels SSA Report 47 April 2018 experienced 484 days (ending October 9, 2009) of no flow due to persistent drought in Central Texas, and approximately 9% of the days exhibited no flow between 1979 to 2009 (BBEST 2011, p. 2-117). Onion Creek below Driftwood ceases to flow, but perennial pools are maintained. The City of Austin, as well as Travis and Hays Counties, and several NGOs have efforts to improve Onion Creek and its watershed. These efforts include buyouts for homes built in the floodplain and subject to flood damage (City of Austin 2018, p. 1a). Additionally, the City of Austin Watershed Protection Department is involved with a suite of conservation programs including riparian area restoration, storm water quality monitoring, bank stabilization, and pursuit of conservation easements. AF 4.C.8 LOWER COLORADO RIVER T As development in the Onion Creek watershed continues, Onion Creek will likely receive additional return flows from treatment plants, and runoff from increased impervious cover in the watershed, leading to alterations in the natural hydrology of the system. The City of Dripping Springs has plans to upgrade its South Regional Wastewater Collection, Treatment, and Disposal Facility, which discharges to Walnut Springs Creek, a tributary to Onion Creek although significant reuse is proposed (City of Dripping Springs 2018, entire). DR This segment of the Colorado River is well below the City of Austin, generally from Columbus to Bay City in Colorado, Wharton, and Matagorda Counties, Texas, and includes portions of TCEQ-classified segment 1402 (Colorado River below La Grange). The hydrology of the Lower Colorado River has been altered significantly following the completion of Buchanan (in 1937) and Mansfield (in 1940) dams, with annual daily average flows ranging from up to 150,000 cfs before 1940 to not more than 40,000 cfs following construction of the dams and the 1950-1956 Drought of Record (at the Austin gage; BIOWEST, Inc. 2008, p. 16). The City of Austin Water Utility is the primary municipal customer of the Lower Colorado River Authority (LCRA 2014a, p. ES-5). The Highland Lakes, specifically Lakes Buchanan and Travis, provide the primary municipal and industrial water supply for the Austin, Texas, metropolitan area. The Austin City Council has launched the Water Forward Task Force to develop a new water plan for the City of Austin: “The goal of the Water Forward plan is to ensure a diversified, sustainable, and resilient water future, with a strong emphasis on water conservation. This plan will consider a range of strategies such as water conservation, water reuse, aquifer storage and recovery (ASR), and others.” (City of Austin 2018c, p. 1). The City of Austin Water Utility manages two major wastewater treatment plants, Walnut Creek and South Austin Regional, with a total permitted capacity of 150 million gallons per day, discharging to the Colorado River below Austin (City of Austin 2018b, p.1). In the Colorado River at Columbus (USGS gage 08161000), it has been determined that the existing channel currently appears to be stable, or perhaps degrading slightly, but reductions in the magnitude and frequency of flows could result in major instability in the future, leading to channel incision and bank collapses (BBEST 2011, p. 3-128). Draft Central Texas Mussels SSA Report 48 April 2018 4.D. GUADALUPE RIVER AND BASIN The Guadalupe River originates from springs in the Texas Hill Country in Kerr County, near Hunt, Texas and flows into the Gulf of Mexico at San Antonio bay after having joined the San Antonio River (Sansom 2008, pp.70, 97-99). The total length of the Guadalupe River is 432 miles (BBEST 2011, p. 2.1). Important tributaries to the Guadalupe River include the Comal, San Marcos, and Blanco Rivers. The Guadalupe River is free-flowing from the confluence with the San Marcos to the Gulf of Mexico, save a saltwater barrier downstream of Victoria, Texas (Sansom 2008, p. 50). T The San Antonio River has a long history of alteration, development, water management, conservation and restoration associated with the San Antonio metropolitan area. The San Antonio River is managed by the San Antonio River Authority, which has jurisdiction in Bexar, Wilson, Karnes and Goliad County (SARA 2018, p.1). Historically, springs contributed much of the baseflow to the San Antonio River, but today flows are largely influenced by wastewater treatment plant discharges (BBEST 2011, p. 2.7). AF The San Marcos and Comal Rivers are supported by important spring systems, which sustain the base flows during periods of low precipitation. During low flow periods, “the springs can contribute much of the base flow of the lower [Guadalupe] river all the way to the estuary” (Sansom 2008, pp. 72-3). While Comal Springs went dry during the 1950-57 “drought of record” (Sansom 2008, pp. 32, 63), spring flows from the San Marcos and Comal Springs systems are now maintained, in part, by protective measures of conservation partners and the Edwards Aquifer Habitat Conservation Plan. It has been estimated that “up to 70% of the flow of the Guadalupe River at the coast during a drought of record is from the San Marcos Springs” (Sansom 2008, p. 194). The Blanco River, another tributary to the Guadalupe River, does not have significant spring influence and ceases to flow during periods of low precipitation. The Blanco River, like many of the Hill Country rivers, is prone to severe flooding (Sansom 2008, p. 73). DR The Upper Guadalupe River Authority (UGRA) was created by the Texas Legislature in 1939 to “protect, develop, and manage the water quantity, quality, and sustainability in the Guadalupe River watershed in Kerr County” Texas (UGRA 2018a, p. 1). The UGRA is the lead “surface water steward for the Upper Guadalupe River (TCEQ segment 1806) and has planned and implemented multiple Clean Water Act projects to improve water quality in Kerr County, Texas (UGRA 2018b, p.1) The Guadalupe Blanco River Authority (GBRA) was created by the Texas Legislature in 1933 and reauthorized in 1935 for “control, storing, preservation and distribution of storm and flood waters, the waters of rivers and streams, including the Guadalupe and Blanco Rivers and their tributaries for irrigation, power, and all other useful purposes” (GBRA enabling act). The Guadalupe Basin provides an important surface water supply for the Region L (South Central Texas; 18% of existing supply) Regional Water Planning Area of Texas and also provides 2% of the existing water supply for Region J (Plateau, TWDB 2016, pp. J-4, L-4). Region L includes the cities of San Antonio, Victoria, Seguin, New Braunfels, and San Marcos, and together derives more than 60% of its existing water supply from groundwater (i.e., aquifer sources). Region J includes the major cities of Del Rio and Kerrville and similarly derives nearly 70% of its existing water supply from groundwater (i.e., aquifer sources). Draft Central Texas Mussels SSA Report 49 April 2018 Canyon Reservoir was completed in 1964 and is managed by the USACE and the GBRA to provide flood control, surface water supply, and hydro-electricity for the City of New Braunfels (GBRA 2018a). Hypolimnetic (deep, cold water) releases support a recreational rainbow and brown trout fishery in an approximately 24-mile segment from below Canyon Dam to the City of New Braunfels (TPWD 2018, p. 1). GBRA is the owner and operator of Lake Dunlap, Lake McQueeney, Lake Placid, Lake Nolte, Lake H-4, and Lake Wood, in Guadalupe and Gonzales Counties, Texas. This series of small hydroelectric dams was completed in 1932 and generate electricity for the Guadalupe Valley Electric Cooperative (GBRAa, p.2). These reservoirs, which are located generally above the confluence with the San Marcos River also provide recreation value for nearby communities. One of these dams experienced a partial failure in March of 2016, dewatering Lake Wood; GBRA has plans to repair this dam and others that make up the Guadalupe Valley Hydroelectric System (GBRA 2018b, p.1). AF T In 2016, following five years of litigation concerning flows and the endangered whooping crane, the GBRA and The Aransas Project (TAP) signed an agreement, which they called a “white paper”, entitled “Affirmation and Restructuring of the Shared Vision for the Guadalupe River System and San Antonio Bay.” This white paper addresses the needs of whooping cranes and their habitats, as well as long-term water supply and flow issues in the basin, and lays out a vision to work cooperatively with stakeholders to achieve a plan “for ensuring water supply, a healthy bay and protected endangered species, including whooping cranes and mussels.” (GBRA-TAP 2016, p.6) This report considers two river segments in the Guadalupe Basin known to support populations of one or more species of Central Texas mussels. 4.D.1 UPPER GUADALUPE RIVER DR This segment of the Guadalupe River is generally from Kerrville to Comfort in Kerr and Kendall Counties, Texas, and includes portions of TCEQ-classified segment 1806 (Guadalupe River above Canyon Lake). A section of the Guadalupe River, near Spring Branch, experienced very low flow conditions (<1 cfs daily mean) during drought conditions from July to October 2011 (USGS 2013a, p. 20). 4.D.2 LOWER GUADALUPE RIVER (AND LOWER SAN MARCOS RIVER) This segment of the Guadalupe River is generally from Gonzales to Cuero, and then on to Victoria in Gonzales, DeWitt, and Victoria Counties, Texas, and includes portions of TCEQ-classified segment 1803 (Guadalupe River below San Marcos River) and 1808 (Lower San Marcos River). The San Marcos River joins the Guadalupe just above Gonzales, Texas. The Blanco and San Marcos are the principal tributaries of the Guadalupe River (USGS 2013b, p.2). The San Antonio River joins with the Guadalupe River near Tivoli, Texas, well below any known mussel populations described in this report. Flows in the Lower Guadalupe River originate primarily from Canyon Lake releases (near the City of New Braunfels), major springs of the Edwards aquifer (Comal, San Marcos, and Hueco Springs), and alluvial base flow (other groundwater seeping into streams), with Canyon Lake and the major springs Draft Central Texas Mussels SSA Report 50 April 2018 contributing most of the streamflow under normal conditions (USGS 2013b, p. 2). Spring flow from Comal Springs, the largest spring in the southwest United States (Brune 1975, p. 39), usually contributes approximately 20% of the flows for the lower Guadalupe River, but during summer months of drought years, spring flow can contribute as much as 50% of the streamflow because of reduced inflows from tributaries and return flows (USGS 2008, p.13). Wolaver et al. (2014) report relatively flat flow duration curves for the Guadalupe River at the Cuero and Victoria gages (08175800 and 08176500, respectively), illustrating the importance of significant stable spring inputs in support stable flow regimes in the Lower Guadalupe River (p. 11). Stable flow regimes are generally considered favorable for the development of diverse and abundant mussel communities. AF T The San Marcos River and, in turn, the Lower Guadalupe River, benefit from spring flow protections associated with the Edwards Aquifer Authority Habitat Conservation Plan (EAHCP), which includes provisions to reduce groundwater pumping when aquifer levels fall below predefined elevations. Thus, spring flows at the Comal River (a 3-mile long spring-fed tributary to the Guadalupe River at New Braunfels, Texas) remain at or above 40 cfs and flows from the San Marcos springs are similarly protected (NAS 2015, p. 36). Because the San Marcos Springs continued to flow during the drought of record of the 1950s, while the Comal Springs ceased to flow, it is assumed that pumping to protect the Comal Springs will also protect the San Marcos Springs, the second largest springs complex in Texas (Brune 1975, p. 45), which are located only 16 miles apart (Sansom 2008, p.63). Thus, flows in the Lower Guadalupe River, contributed by the Comal and San Marcos Rivers, are relatively secure given management and conservation efforts by the EAHCP and partners (NAS 2015, p. 36). As part of the EAHCP, a Watershed Protection Plan (WPP) has been proposed for the Upper San Marcos River that includes those areas in the vicinity of the City of San Marcos and Texas State University (Gleason et al. 2016, entire). DR Perkin and Bonner (2011) documented changes in fish communities and changing flow regimes in the Guadalupe and San Marcos Rivers, following the completion of several low head dams on both rivers and the 1964 construction of Canyon Reservoir on the Guadalupe River. In the Upper Guadalupe River near Spring Branch, mean annual flow and frequency of small and large floods increased (Perkin and Bonner 2011, p. 569). In the Lower Guadalupe River near Victoria, mean annual flow increased while the frequency of small and large floods decreased (Perkin and Bonner, p. 569). In the San Marcos River near Luling, mean annual flow increased while the frequency of small and large floods decreased (Perkin and Bonner 2011, p. 570). These changes were attributed to both low flows during the “drought of record” in the 1950’s and by the construction of dams and other flood control structures (Perkin and Bonner 2011, p. 574). In general, these shifts in flow regimes favored fishes that were “habitat generalists” rather than “fluvial specialists” while the fish assemblages remained relatively intact (Perkin and Bonner 2011, p. 575). The City of San Marcos’ municipal supply is approximately 75% surface water from Canyon Lake (Guadalupe River) and 25% groundwater from the Edwards Aquifer (City of San Marcos 2018a, p. 1). The City of San Marcos operates a “high-quality wastewater treatment plant and water system rated superior by the State of Texas” (City of San Macros 2018b, p. 1) that discharges into the San Marcos River below the City of San Marcos. Draft Central Texas Mussels SSA Report 51 April 2018 4.E TRINITY RIVER AND BASIN The Trinity River originates as several forks (West Fork, Clear Fork, Elm Fork, East Fork) originating in North Central Texas and combining near Dallas, Texas, where the Trinity River supplies municipal water to over 6 million residents of the DFW metropolitan area, and flows into the Gulf of Mexico at Trinity Bay (and Galveston Bay) below Lake Livingston which provides municipal water for the Houston metropolitan area, which includes over 6 million resident (Sansom 2008, pp. 55, 88). The total length of the Trinity River is 550 miles, wholly in Texas (TWDB 2018). The Trinity is the only basin in Texas that provides water to both a major metropolitan area in the upper basin and a major metropolitan area in the lower basin (TRA 2017, p. 41). AF T The Trinity River Authority (TRA) was created by the Texas Legislature in 1955 and owns and operates Lake Livingston Dam, which was completed to form Lake Livingston in 1971. Reuse has been a major part of the TRA’s water planning strategy following the 1950-57 drought. Reuse rights were contemplated when construction of Lake Livingston was constructed on the Trinity in 1969 to provide municipal water the City of Houston, and reuse continues to represent a significant portion of TRAs water supply (TRA 2012, pp. 35-6). There are a total of 32 major reservoirs in the Trinity River Basin (TWDB 2018, p. 1). There remains an undammed segment of the “Middle” Trinity River between RichlandChambers and Livingston Reservoirs. The Tarrant Regional Water District provides water supply, flood protection, and recreation opportunities for residents of Tarrant County, Texas, and owns and operates four major reservoirs, including Lake Bridgeport, Eagle Mountain Lake, Cedar Creek Lake, and Richland-Chambers Lake. The RichlandChambers Dam and Reservoir was completed in 1989 and built on two tributaries to the Trinity River, Richland, and Chambers Creeks (TWDB 2018, p. 1). DR The Trinity Basin provides an important surface water supply for the Region C (49% of existing supply) and Region H (42% of existing supply) Regional Water Planning Area of Texas (TWDB 2016, pp. C-4, H-4). Region C includes the Dallas-Fort Worth metropolitan area and Region H includes the Houston metropolitan area; these two Regions are expected to provide over half of the State’s population growth over the next fifty (50) years, between 2020 and 2070 (TWDB 2017, p.3). Additional flows from other river basins, such as the Sabine and Sulfur contribute to the return flows to the Trinity River. The Upper Trinity River Water Quality Compact (Compact) was created in 1975 to improve water quality, such that return flows can now be reused, and water rights assigned to reused return flows such that some percent of discharges are guaranteed to downstream users (TRA 2017, p. 41). Approximately 30% of the Tarrant River Authority’s return flows are to Lake Livingston (TRA 2017, p. 41), and reuse flows alone are apparently adequate to meet established environmental flow prescriptions for the Trinity River (TRA 2017, pp. 42, 49). Return flows contribute more than 90% of the flow to the Trinity River below Dallas during prolonged dry periods (TRA 2012, p.49) and thus base flow is artificially elevated. Low flows in the Trinity River have been increasing over since 1939, with increasing volumes of wastewater discharged from the Dallas-Fort Worth area (measured at the Trinity River at Rosser USGS gage 08062500; BBEST 2009, p. 11). Draft Central Texas Mussels SSA Report 52 April 2018 The North Texas Municipal Water District (NTMWD) is a public water utility that services the northeast portion of the Dallas-Fort Worth metropolitan area including Collin County, Texas, and the East Fork Water Reuse Project, a 1840-acre wetland project that diverts water from the East Fork of the Trinity River and pumps it back to Lavon Lake and the Wylie Water Treatment Plan for drinking water (NTMWD 2018a, p. 1). NTMWD’s TCEQ permit provides for minimum flows at the John Bunker Sands wetlands of 26 cfs, which represents approximately 30% of the local basin return flows to the East Fork of the Brazos River (NTMWD 2018b, p. 2). AF T The Trinity River in the Dallas Fort Worth metropolitan area has a long history of transfer of water from other basins including the Red, Sulfur, and Sabine. For example, Neck (1990) notes that during the drought of the 1950’s, over 90,000-acre-feet of water was diverted from the Red River into Lake Dallas (now part of Lake Lewisville; p.17) on the Elm Fork of the Trinity River. The Trinity River near Oakwood, Texas, is the site of USGS stream gage 080650000, and this “control point” has established subsistence, base, and pulse flows defined for winter, spring, summer, and fall (TCEQ 2011e, p.6). The annual minimum flow at USGS gage 0806500 near Oakwood, Texas has increased from less than 200 cfs to more than 400 cfs since 1930, due to return flows and transfers from other basins (TRA 2017, p. 42). During periods of low rainfall, the flow in the mainstem Trinity River between Dallas and Lake Livingston is almost entirely wastewater effluent (i.e., return flows; TRA 2012, p. 24). Today, because of a combination of “reservoir management, wastewater discharges, and flows imported from other watershed” streamflows in the main stem Trinity River in the summer are higher than they would have been under natural conditions (Sansom 2008, p. 56). DR The Trinity River has a long history of water quality impairment (Randklev et al. 2010, p. 2366), particularly between Dallas and Lake Livingston, but recent improvements following decades of wastewater treatment upgrades (reviewed in USGS 1998, entire) have led to the at least partial recovery of fish over the past 40+ years (Perkin and Bonner 2016, p. 91; entire for full discussion) and benthic macroinvertebrate communities. Frequent summer fish kills occurred in the 1980s to early 1990s as high flow events disturbed previously buried organic matter, resulted in anoxic conditions (i.e., the “black rise”; BBEST 2009, p. 66). This report considers two river segments in the Trinity Basin known to support populations of one or more species of Central Texas Mussels. 4.E.1 LOWER EAST FORK OF THE TRINITY RIVER This segment of the East Fork of the Trinity River is generally below Seagoville in Tarrant County, Texas, to the confluence with the main stem of the Trinity River, and includes portions of TCEQ segment 0819 (East Fork Trinity River). The East Fork Water Reuse Project was completed in 2009 and diverts some flows from the East Fork to a created wetlands complex for treatment and ultimate reuse (i.e., the John Bunker Sands Wetland Center, NTMWD 2018a, p. 1). Draft Central Texas Mussels SSA Report 53 April 2018 4.E.2 MIDDLE TRINITY RIVER This segment of the Trinity River is generally between Richland-Chambers Reservoir and Lake Livingston, above and below Oakwood, Texas, in Anderson, Freestone, Houston, Leon, and Madison Counties, and includes portions of TCEQ segment 0804 (Trinity River above Lake Livingston) and TCEQ segment 0803 (Lake Livingston). In the Trinity River at Oakwood (USGS gage 806500) flows have increased since 1955 as return flows increased (BBEST 2009, p. 268).   DR AF   T Randklev et al. (2017a, p.7) observe that peak floods occur frequently (approximately annually or more frequent) in the Trinity River, and hypothesize that water management practices, which result in discharges >= 400 m3/s appear to be limiting mussels in bank habitats and having negative impacts on mussel communities and populations in the middle Trinity River. Draft Central Texas Mussels SSA Report 54 April 2018 CHAPTER 5 ‐ CURRENT CONDITIONS 5.A GENERAL CURRENT CONDITIONS OF CENTRAL TEXAS MUSSELS This assessment defines a mussel population as a stream reach that is a collection of mussel beds through which host fish infested with glochidia may travel, allowing for dispersal of juveniles among and within mussel beds. This chapter discusses the current populations of each species and assesses the resiliency of each population. METHODOLOGY FOR POPULATION RESILIENCY ASSESSMENT AF T For each species and each population, we developed and assigned condition categories for three population and habitat factors (See Chapter 3.C Needs of Central Texas Mussels). The population factor for occupied habitat was calculated using ArcGIS by summing the stream miles between locations known to be occupied in since 2000 for the whole population. The other five factors were scored by U.S. Fish and Wildlife Service biologists as informed by information available in our files. For each population, the six categories were assigned a numerical value: 3 for healthy, 2 for moderately healthy, 1 for unhealthy, and 0 for extirpated or functionally extirpated. For each population, these six factors were averaged and the average condition value was then compared with the individual category value for population abundance. In determining the overall condition, no overall condition was allowed to exceed the population abundance (i.e., overall population condition was capped at the population abundance condition). The current condition category is a qualitative estimate based on the analysis of the three population factors and three habitat elements. Table 5.1 displays the presumed ranges of probabilities of the persistence of a population with a given current condition category over 50 years (about three to five mussel generations). DR Table 5.1. Presumed probability of persistence for overall current condition categories. Likelihood of Persistence: Healthy Moderately Healthy Unhealthy Extirpated/Functionally Extirpated Range of Presumed Probability of Persistence over ~50 years 90 – 100% 60 – 90% 10 – 60% 0 – 10% Range of Presumed Probability of Extirpation over ~50 years 0 – 10% 10 – 40% 40 – 90% 90 – 100% Draft Central Texas Mussels SSA Report 55 April 2018 5.B FALSE SPIKE 5.B.1 CURRENT DISTRIBUTION   False spike was suspected of being extinct until living individuals were discovered in four locations in the Guadalupe, Colorado, and Brazos River basins in 2011-2013 (Howells 2014, p. 85). Randklev et al. (2017, p.11) surveyed 130 sites in the Brazos, Colorado, and Guadalupe River drainages and found a total of 31 live false spike individuals from eight 8 locations (Figure 5.1). Twenty-two of these individuals were from the Little River. When summed together, the currently occupied stream length of all four false spike populations combined equals 186 stream miles, which equates to approximately 3.7% of the presumed 4,792 stream mile historical range for the species. L ITTLE R IVER T   AF False spike is known to occur within the Brazos River basin only in the Little River and two tributaries, Brushy Creek and the San Gabriel River. In the Little River main stem, false spike occupies 5.2 stream miles from the FM 1915 bridge crossing downstream to the confluence with the San Gabriel River, all in Milam County. In the San Gabriel River, false spike occupies 17.9 stream miles between the FM 428 bridge crossing downstream to the CR 428 bridge crossing, in Williamson and Milam counties, Texas. In Brushy Creek, false spike occupies only 2.9 stream miles from the FM 908 bridge crossing downstream to the confluence with the San Gabriel River, all within Milam County, Texas. DR False spike was discovered in the Little River basin in 2012 from the lower San Gabriel River in Milam County, Texas, and in 2012 and 2013, 3 live individuals in run habitats with cobble/gravel substrate were documented (Randklev et al. 2013a, pp. 18-19). The Little River is not known to have been surveyed for mussels prior to 2012. Randklev et al. (2017, p.11) found 29 live individuals in the Little River in 2015 during qualitative (n=22) and quantitative surveys (n=7), noted some evidence of reproduction and that most of these individuals were found in riffle habitats. Two live individuals (with some evidence of brooding) were reported in riffles in the San Gabriel River (a tributary to the Little) just below Granger dam, 5 live individuals (with some evidence of brooding) from Brushy Creek near the confluence with the San Gabriel (Randklev et al. 2017, p.17). Bonner et al. (2018) report searching for, but not finding any false spike in the Little River basin (p. 26), but do report “recently dead shells with nacre still intact” (p. 21). Draft Central Texas Mussels SSA Report 56 April 2018 T AF DR Figure 5.1 Location of each of the four current populations of the false spike in the Brazos, Colorado, and Guadalupe Rivers. Draft Central Texas Mussels SSA Report 57 April 2018 L OWER S AN S ABA R IVER The current population of false spike in the San Saba River is known to occur from the CR 340 bridge crossing downstream to the confluence of the San Saba River with the Colorado River. This population occupies approximately 41.8 stream miles of the San Saba River in San Saba County, Texas. T The Lower San Saba River population of false spike appears to be in decline. In 2012, 3 live individuals were found at two sites in the lower San Saba River, in San Saba County, Texas. There was evidence of possible reproduction (oocytes in sampled gonadal fluid) and individuals were collected from coarse gravel habitats adjacent to runs (Randklev et al. 2013a, p. 19). One of these individuals was previously reported by Sowards et al. (2013, p. 64) who reported finding a single live individual from a riffle habitat in the San Saba River “11.3 km east of the City of San Saba” in July 2012. Tsakiris and Randklev (2014, p. 11) reported finding one live false spike at each of two locations (CR 340 and CR 126 bridge crossings). L LANO R IVER   AF Randklev et al. (2017c, p.11) returned to the San Saba River and found no live individuals in the San Saba River. Recently, Bonner et al. (2018, entire) surveyed two sites in the San Saba River and found no live individuals and no shell material. Randklev et al. (2017c, p. 12) report that historic museum records indicated that false spike had been collected from the upper San Saba River in Menard County, Texas, by Simpson in 1914 and by Strecker in 1931. DR The Llano River population of false spike is by far the smallest population, is known to persist only in the immediate vicinity of the FM 1871 bridge crossing in Mason County, Texas. This population is less than one mile in length and likely is made up of only a few small mussel beds. Because of easy highway access and close proximity to major cities, this population is frequently sampled by mussel collectors and researchers. The Llano River population of false spike appears to be very small. Randklev et al. (2013a, p. 19) report finding a single live individual from the Llano River near Mason, Texas, in August 2013, from a small pool habitat with gravel/cobble substrate. Service biologists (USFWS 2017, p. 2) found one live individual in the Llano River near Mason, Texas during a reconnaissance survey. This live individual was 35mm long indicating that a recent reproduction event had occurred, approximately 1-5 years before. Additionally, one dead false spike was recovered from the site and showed signs of depredation, presumably by a raccoon; this mussel < 40 mm in total length and assumed to be a sub-adult. The dead false spike was discovered in the small spaces between large cobble in a shallow edge habitat. Randklev et al. (2017c, p.11) found only one live individual, in a pool, out of 20 sample sites. The individual was 37 mm in total shell length. While no evidence of reproduction was noted, recent reproduction is inferred based on the size of the sub-adult individual. Bonner et al. (2018, entire) found no live individuals during recent sampling of the FM 1871 site in the Llano River. Draft Central Texas Mussels SSA Report 58 April 2018   L OWER G UADALUPE R IVER   The Lower Guadalupe River population of false spike extends for 102.6 stream miles from the Highway 111 bridge crossing near Gonzales, Texas, downstream to the FM 447 bridge crossing near Victoria, Texas. This population occurs in Guadalupe River in Gonzales, DeWitt, and Victoria counties, Texas. T The Lower Guadalupe River population of false spike is the largest population known for the species. The most recent surveys that documented living individuals were conducted in 2011, by Randklev et al. 2011 (pp. 17-18) who report finding 7 live individuals, from near the edge of a gravel bar, in the Guadalupe River near Gonzales, Texas. Mabe and Kennedy (2013, pp. 298-9) observed eight living false spike and collected recent shells from stable substrates in “a shallow run just upstream of a moderatelysized riffle” of the Lower Guadalupe River near Cuero, Texas, in 2012. AF The most comprehensive survey of the Lower Guadalupe River was completed in 2014-15 when Tsakiris and Randklev (2016a, p. 13) observed a total of 652 false spike out of a total of over 21,000 mussels. False spike was observed only from riffle habitats, and not below Cuero, Texas, indicating very low abundances in the reaches just above Victoria, Texas. Bonner et al. (2018, p. 37) found no living individuals in the upper Guadalupe River. 5.B.2 AREAS PRESUMED EXTIRPATED   DR False spike is presumed to have been extirpated from much of its historical range throughout the Brazos, Colorado, and Guadalupe Basins of Central Texas (reviewed in Randklev et al. 2017c, pp. 12-13). In fact, false spike was thought to be extinct for nearly 40 years, since the 1970s (Burlakova and Karatayev 2012, p. 13) until the species was rediscovered in 2011 (Randklev et al. 2011, entire). False spike was previously thought to have occurred in the Rio Grande Basin (Randklev et al. 2013a, p.19) but those specimens have since been assigned to Sphenonaias taumilapana (Pfeiffer et al. 2016, p. 285). False spike is now absent from the Leon River (Randklev et al. 2013, p. 390), but historically occurred in there, based on archaeological evidence (shell middens; Popejoy et al. 2016, p. 477). Randklev et al. (2017c, p. 11) report searching for, but not finding any false spike in the San Saba and Pedernales rivers. Bonner et al. (2018) report searching for, but not finding any false spike in the Upper Guadalupe basin and Middle Colorado basin (p. 26), and in the Lower Colorado basin (p. 12). 5.B.3 CURRENT CONDITIONS   To summarize the overall current conditions of false spike populations, we assigned each population to one of three categories (healthy, moderately healthy, unhealthy, or functionally extirpate) based on the population factors and habitat elements discussed in Chapter 3 and as displayed in Table 5.2. Table 5.3 presents the overall condition of false spike populations as displayed in Figure 5.2. Draft Central Texas Mussels SSA Report 59 April 2018 Table 5.2. Population and habitat characteristics of false spike populations used to assign condition categories in Table 5.3. Habitat Factors Population Factors Condition Abundance Found in nearly all available habitats surveyed. More than 100 individuals found per population survey. Substrate Riffle and run habitats present. Gravel and 50% or more sites with cobble substrates juveniles (< 35 mm) and sufficient to provide gravid females present lodging habitat. Very during the breeding season low evidence of and fish hosts present. excessive sediment in the substrate matrix. > 50 river miles Moderately Healthy Found in approx. 50% of all available habitats surveyed. 49-20 river miles Between 26 – 99 individuals found per population survey. Extirpated/ Functionally Extirpated < 19 river miles none Flowing Water Water Quality Flowing water present yearround. Water levels sufficient to keep known habitats constantly submerged. No documented habitat exposure. No known incidence of contaminant spills, low dissolved oxygen, or evidence of exposure extreme high or low temperatures 25-50% of sites having juveniles (< 35 mm) and gravid females present during the breeding season and fish hosts present in at least moderate abundance. Flowing water present almost year-round. Few instances of zero flow days and minimal exposure of portions of known habitats to dewatering. Contaminants known, low dissolved oxygen and temperature extremes documented. Levels not high enough to risk extirpation. Riffle and run habitats eroded, unstable, or being buried by mobilized sediments from upstream sources. Flowing water not present year-round. Summer records of zero flow days. However, at least some pools stay sufficiently wetted, cool, and oxygenated. Known exposure to contaminants, low dissolved oxygen, and documented cases of excessive water temperatures extremes. Water quality parameters diminished such that exposure threatens mussel survival. No suitable habitat present. Streambed dry or the number of zero flow days high Water quality degradation such enough to result in dewatered that occupancy of otherwise habitats, precluding survival suitable habitat is precluded. of mussels. Riffle and run habitats present. Gravel and cobble substrates sufficient to provide lodging habitat. Low levels of excess sediment in the substrate matrix. DR Healthy Unhealthy Reproduction AF T Occupied Habitat Found in few areas of suitable habitat. Between 2 – 25 individuals found per population survey. < 25% of sites inhabited by juveniles (<35 mm) and gravid females present during the breeding season and fish host present in low abundance and/or ability to disperse is reduced. Very few or no live individuals documented during surveys (< 1). No evidence suggesting that juveniles or gravid females are present. Fish host not known to occur. Draft Central Texas Mussels SSA Report 60 April 2018 Table 5.3. Current condition of known false spike populations. False Spike Population Factors Basin Stream Length Population Habitat Factors Flowing Water Abundance Reproduction Substrate Water Quality Overall Condition Lower San Saba Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Llano Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Healthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Guadalupe Little DR Brazos Lower Guadalupe AF T Colorado Draft Central Texas Mussels SSA Report 61 April 2018 T AF DR Figure 5.2. Location and current overall condition for each of the four populations of the false spike in the Brazos, Colorado, and Guadalupe River basins. Draft Central Texas Mussels SSA Report 62 April 2018 5.B.3 A C URRENT P OPULATION R ESILIENCY   Currently, the false spike is known to exist as four populations occurring in three separate river basins: the Brazos, Colorado, and Guadalupe. In the Brazos basin, false spike is currently known to exist only in the Little River basin, a tributary to the Brazos River. Within the Little River population, the species exists in the San Gabriel River, Brushy Creek, and main stem Little River. This single population is quite small and has an overall unhealthy current condition and, therefore, low resiliency. T The Colorado River basin has two known populations: the lower San Saba River and Llano River populations. These two populations are rather small and isolated from one another and considered to be in unhealthy condition overall, corresponding to low resiliency. Within the Guadalupe River basin, false spike is known from one population: the lower Guadalupe River. This is the largest and most robust known population and is the only population currently in the moderately healthy condition.   AF 5.B.3. B C URRENT S PECIES R EPRESENTATION We consider the false spike to have representation in the form of genetic and ecological diversity in each of three basins: Brazos, Colorado, and Guadalupe. As discussed in Chapter 2, there is preliminary genetic information that the Guadalupe basin differs significantly from the other basins, and because there is no freshwater connection between the three basins, we treat each population as a separate area of representation. DR 5.B.3. D C URRENT S PECIES R EDUNDANCY   Within these identified representation areas, the Brazos and Guadalupe River basins each have only one known current population and therefore lack any redundancy. The Colorado River basin has two separate populations, providing only limited redundancy. 5.C TEXAS FATMUCKET 5.C.1 CURRENT DISTRIBUTION Texas fatmucket appears to be currently restricted to upper reaches of major tributaries within the Colorado River Basin (Randklev et al. 2017, p. 4), as well as in the upper Guadalupe River basin (Figure 5.3). The total current distribution of Texas fatmucket, summed across the six populations from the Colorado and Guadalupe River basins, is a combined stream length of approximately 331.4 miles. This current distribution represents approximately 19.5% of the total presumed historic range of 1,702.9 stream miles. Draft Central Texas Mussels SSA Report 63 April 2018 T AF DR Figure 5.3. Location of each of the six current populations of Texas fatmucket in the Colorado and Guadalupe Rivers. Draft Central Texas Mussels SSA Report 64 April 2018 L OWER E LM C REEK   The Texas fatmucket currently occupies about 8.7 stream miles of the Elm Creek. This population extends from the CR 330 bridge on Elm Creek downstream to the confluence with the Colorado River in Runnels County, Texas. Howells (2006, p. 63) noted that live individuals of Texas fatmucket were encountered in surveys during 1993 (10 live) and 1995 (2 live). Since that time only two dead shells were noted during surveys in 2005 at this same site (Elm Creek near FM 216). U PPER /M IDDLE S AN S ABA R IVER   T Burlakova and Karatayev (2010) reported collecting 1 live and 1 recently dead Texas fatmucket Elm Creek at County Road 261 in Runnels County in 2008 and report that none were found in the Colorado River west of Ballinger or from Bluff Creek north of Ballinger (p. 12). AF The population of Texas fatmucket is known to persist between the US 190 and U S87 bridge crossings of the San Saba River and inhabits a total of 62 river miles across Menard, Mason, and McCulloch counties, Texas. Early reports of Texas fatmucket in the upper San Saba River are limited. Burlakova and Karatayev (2010) report finding 1 live Texas fatmucket in the San Saba River in Menard County in 2005 (p. 12). Howells (2006, p. 64) noted that 1 live Texas fatmucket was encountered during surveys in July 2005 and one half-shell. At the same site, 3 live individuals were noted in during surveys in 1997. DR Additional surveys continued to find low numbers of individuals. Braun et al. (2012, pp. 5, 14) report that three sites were surveyed in the San Saba River basin and at one location (Beyer Road Crossing, near Bois D’Arc Creek) 8 live individuals were collected as well as shell material of various ages. Service biologists found a total of 5 live Texas fatmucket during two separate surveys near the Bois D’Arc crossing on the San Saba River in 2013 (Braun et al. 2014, pp. 14-15). Tsakiris and Randklev (2014, p. 11) reported finding no live Texas fatmucket (or dead shell) from two locations, CR 340 and CR 126 bridge crossings, during surveys for other species. More recent surveys were focused on known locations. In 2016, Service biologists (USFWS 2017, pp. 35) reported finding a total of 29 live Texas fatmucket at two sites in the San Saba River in Menard and McCulloch counties, Texas. Seagroves and Schwalb (2017, p. 11) reported finding 87 live Texas fatmucket from a single site following multiple sampling events in 2016. Randklev et al. (2017) report finding 71 live Texas fatmucket from 6 of 19 sites in the San Saba River, in Menard and McCulloch counties, Texas (pp. 42, 50). Draft Central Texas Mussels SSA Report 65 April 2018 L LANO  R IVER    The Llano River population of Texas fatmucket extends from the lower 20.9 miles of the South Fork of the Llano River to the mainstem of the Llano River for an additional 89.6 miles to the City of Llano’s second municipal water storage lake, known as Llano City Lake. In addition to the mainstem Llano River, two of its tributaries the James River and Threadgill Creek are occupied with 11.5 and 5.4 stream miles, respectively. This accounts for a total of 127.4 stream miles of occupied habitat. The Llano River population is found in Kimble, Mason, and Llano counties, Texas, and includes a very small section of Threadgill Creek extending into northern Gillespie County. AF T In the Llano River, Texas fatmucket can be locally abundant. Burlakova and Karatayev (2010) report in August 2009 finding 3 live and 2 recently dead Texas fatmucket, in the Llano River “in the roots of cypress trees and other vegetation along steep banks” including at the FM 385 crossing near Yates in Kimble County, (pp. 12-3). Sowards et al. (2012) report finding 33 live Texas fatmucket from the FM1871 crossing of the Llano River in Mason County, Texas, from “crevices in the bedrock containing loose deposits of silt and gravel” (p.4). Braun et al. (2012, p. 14) report finding no live but fresh dead (mantle tissue present) shells at two sites in the Llano River near Castell (FM 2768) and Junction, Texas (CR 385). TPWD biologists (2015) reported finding a total of 11 live Texas fatmucket near Sutton County Park on the North Fork of the Llano River. However, due to downstream water quantity issues (the North Fork of the Llano River dries during summertime drought conditions) this location is most likely isolated from other individuals in the Llano River system. DR Service biologists (USFWS 2016, p. 1) found 10 live Texas fatmucket from one site in the Llano River near Mason, Texas. This site was sampled on two different occasions, and the survey focus areas did not overlap (e.g. upstream of the bridge and downstream of the bridge), so recorded individuals are not likely to be repeat captures. A number of surveys occurred in 2017 including Randklev et al. (2017c) who report finding 47 live Texas fatmucket from 7 of 20 sites in the Llano River (p. 42), in Mason and Llano Counties, Texas (p. 50). Additionally, Service biologists (USFWS 2017, p. 10) found five Texas fatmucket during a presence/absence survey at one location near Mason, Texas. Notes indicate that several individuals appear to be female and shell length measurements suggest that one was a juvenile (i.e., evidence of reproduction and subsequent recruitment). Seagroves and Schwalb (2017, p. 11) reported finding 72 live Texas fatmucket from one site during multiple surveys in 2016. BIO-WEST, Inc. (2018) reported capturing and removing 635 Texas fatmucket from Llano Park Lake on the Llano River near the City of Llano in Llano County, Texas, during a reservoir drawdown and complete dewatering event that occurred in November/December 2017 (pp. 2-3). These individuals represented a range of size classes (p. 3). Approximately 90 of these individuals, which were collected for use in ongoing research projects. The remaining individuals were relocated 2-3 miles downstream (p. 3). No information about the survival of these translocated individuals was available at the writing of this report. Draft Central Texas Mussels SSA Report 66 April 2018 P EDERNALES R IVER   The Texas fatmucket is currently known to persist in the Pedernales River from the confluence of Live Oak Creek downstream to about the RR 3238 bridge crossing. This population also extends 2.5 stream miles upstream into Live Oak Creek. Presumably, these locations are connected and experience gene flow by host fish movements. In total, the Pedernales River population occupies 78.8 stream miles, including the section of Live Oak Creek. This population is largely contained in Gillespie and Blanco Counties with a small section of the Pedernales River reach extending into Hays County, Texas. T Texas fatmucket is known from the Pedernales River and several tributaries. Howells (2004, p. 8) reported 1 live and one shell with multiple single valves present in Live Oak Creek in 2003. Howells (2006, p. 65) reported 17 dead shells in 2004 and two live and three dead shells from 2005 during multiple surveys at the same site in Live Oak Creek. Additionally, Burlakova and Karatayev (2010) reported collecting 2 live Texas fatmucket in from Live Oak Creek (Gillespie County, Texas) in 2005 (p. 12). AF Johnson et al. (2011) report finding 1 partially gravid female Texas fatmucket downstream of the Boos Lane Crossing of the Pedernales River in Gillespie, County, on April 22, 2011 (pp. 3-4), and Braun et al. (2012, p.14) reported finding no live but fresh dead (mantle tissue present) at the same site the following year. Sowards et al. (2012) report finding 1 Texas fatmucket under the US 290 crossing of Rocky Creek (a Pedernales tributary) in Blanco, County, “in a loose gravel patch” (p. 4). Randklev et al. (2017) reported finding 18 live Texas fatmucket from 7 of 19 sites in the Pedernales River (p. 42), including 4 individuals from 2 sites in bank habitats in Live Oak Creek, and 7 individuals from a site upstream of the confluence with Live Oak Creek (near Fredericksburg, in Gillespie County, Texas; pp.43, 50). L OWER O NION C REEK DR   The Texas fatmucket population in Onion Creek is one of the smallest known. This population only occurs in the 5-mile stream reach from just upstream of the US Hwy 71 crossing to the Onion Creek and Colorado River confluence. This population is made up largely of only a handful of singleton individuals that were found in the early 2000s and have not been detected in recent years (see below for further discussion). The Onion Creek population is located entirely within Travis County, Texas. This very small population has most likely become extirpated relatively recently. Wilkins et al. (2011) report finding 3 live Texas fatmucket near the SH 71 crossing of Onion Creek, in August 2010 (p. 9). However, subsequent surveys in 2012, 2013, and 2018 have yielded no live or fresh dead Texas fatmucket (Sowards et al. 2012, p. 5; Cordova et al. 2013, p. 1; Bonner et al. 2018 p. 7; Inoue 2018, p. 1). Inoue (2018, p. 1) searched for Texas fatmucket near the US Hwy 71 crossing of Onion Creek with SCUBA for about 2.5 hours and found no sign of living or dead shell Texas fatmucket, but noted some more common species, including yellow sandshell and giant floater. Surveys noted that habitat consisted of a clay bottom with a silt and fine sand matrix, a habitat condition not expected to be suitable for Texas fatmucket. Draft Central Texas Mussels SSA Report 67 April 2018 U PPER G UADALUPE R IVER This population extends from the origination of the Guadalupe River mainstem (where the North and South Fork Guadalupe Rivers converge) to the Hwy 27 crossing near Comfort, Texas. The Texas fatmucket population in the Guadalupe River is 35.6 stream miles in length and found in Kerr and Kendall counties, Texas. Texas fatmucket have been found consistently in low numbers in the Upper Guadalupe River. Howells (2000) reports a collection of 2 and one-half Texas fatmucket shells by Upper Guadalupe River Authority from the North Fork of the Guadalupe River upstream of Hunt, Texas, at FM 1340 in Kerr County (p. 27). Subsequently, Howells (2006, p. 72) reports twenty dead Texas fatmucket shells from a survey in 1998 and one dead shell and 6 live individuals from the same site in 2005. AF T Burlakova and Karatayev (2010) reported collecting 6 live Texas fatmucket in from the Guadalupe River in Kerr County in 2005 (p.12). Service biologists (USFWS 2013, p. 1) found 2 live Texas fatmucket downstream of the dam near Hayes Park in Kerr Co in 2013. During this survey it was noted that females were displaying mantle lures; therefore, we presume these females were gravid. Bonner et al. (2018) report finding, 16 Texas fatmucket from 4 sites in the Upper Guadalupe River between Hunt and Center Point, in Kerr County, Texas (p. 19) in bank and pool habitats (p. 24). Inoue (2018, entire) searched for Texas fatmucket near the Ehlers Road crossing of the Guadalupe River and found 22 living Texas fatmucket. These individuals were collected and removed from the wild for ongoing genetic work. These individuals from the Guadalupe River are likely an undescribed Lampsilis species and not true Texas fatmucket (see Chapter 2 more discussion). 5.C.2 AREAS PRESUMED EXTIRPATED DR Texas fatmucket is historically known from the upper portions of the Guadalupe and Colorado Basins and is not thought to have occurred in the lower portions of those basins in the “coastal plain” (Howells 2014, pp. 41-2; and reviewed in Randklev et al. 2017, pp. 39-40). While several lone individuals were found in the Middle Colorado River (Bonner et al. 2018, pp. 20, 29), existing data do not support evidence of a population. This small, isolated watershed likely does not represent a currently reproducing population. Bonner et al. (2018) report searching for, and not finding, Texas fatmucket from Pecan Bayou (p. 7). The middle portion of the San Saba River regularly goes dry, and the 2011-2012 drought had a particularly large impact on this reach. Burlakova and Karatayev (2012, p. 14) found 65 very recently dead individuals in this area of the river during this drought. Scattered individuals may still persist in this reach, but existing data do not suggest evidence of a reproducing population. 5.C.3 CURRENT CONDITIONS OF TEXAS FATMUCKET To summarize the overall current conditions of Texas fatmucket populations, we sorted them into three categories (healthy, moderately healthy, and unhealthy) based on the population factors and habitat elements discussed in Chapter 3 and displayed in Table 5.4. Table 5.5 shows the overall condition of Texas fatmucket populations, as displayed in Figure 5.4. Draft Central Texas Mussels SSA Report 68 April 2018 Table 5.4. Population and habitat characteristics of Texas fatmucket populations used to create condition categories in Table 5.5. Habitat Factors Population Factors Occupied Habitat Condition Reproduction Substrate Healthy > 50 river miles Found in nearly all available habitats surveyed. More than 100 individuals identified per population survey. 50% or more sites with juveniles (<35 mm) and gravid females present during the breeding season and fish hosts present. Bedrock fissures and/or vegetative crevices present. Substrate sufficient to provide anchoring within crevices but not filled with sediment. Flowing water present yearround. No recorded periods of zero flow days. Water levels sufficient to keep known habitats submerged. No known incidence of contaminant spills, low dissolved oxygen, or evidence of exposure extreme high or low temperatures Moderately Healthy Found in approximately half all available habitats 49-20 river miles surveyed. Between 26 – 99 individuals identified per population survey. 25-50% of sites inhabited by juveniles (<35 mm) and gravid females present during the breeding season and fish hosts present in moderate abundance. Bedrock fissures and crevices present. Substrate sufficient in places to provide anchoring while other areas scoured or too heavily filled with sediment. Flowing water present almost year-round. Few instances of zero flow days or minimal exposure of portions of known habitats. Contaminants known, low dissolved oxygen and temperature extremes documented. Levels not high enough to risk extirpation. Known exposure to contaminants, low dissolved oxygen, and documented cases of excessive water temperatures extremes. Water quality parameters diminished such that exposure threatens mussel survival. DR Unhealthy Extirpated/ Func. Extirpated Flowing Water Water Quality AF T Abundance < 19 river miles < 25% of sites inhabited by juveniles (<35 mm) and Found in few areas gravid females present of suitable habitat. during the breeding season Between 2 – 25 and fish host present in individual identified low abundance and/or per population ability to disperse is survey. reduced. Fissures and crevices obstructed with excess sediment. Relatively high amount of sedimentation and filling of interstitial spaces. Flowing water does not persist year-round. Summer records of zero flow days while pools stay wetted and sufficiently cool and oxygenated. none Very few or no live individuals identified during surveys (< 1). No suitable habitats present. Dry stream bed or zero flow Water quality degradation such days high enough to preclude that occupancy of otherwise survival. suitable habitat is precluded. Draft Central Texas Mussels SSA Report No evidence suggesting that juveniles or gravid females are present. Fish host not known to occur. 69 April 2018 Table 5.5. Current condition of Texas fatmucket populations. Texas fatmucket Population Factors Colorado Unhealthy Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Moderate Moderate Moderate Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Pedernales Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Onion Creek Functionally Extirpated Functionally Extirpated Functionally Extirpated Unhealthy Moderate Unhealthy Functionally Extirpated Guadalupe Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Reproduction Elm Creek Unhealthy Unhealthy San Saba Healthy Llano DR Guadalupe Overall Condition Abundance Population AF T Basin Habitat Factors Flowing Water Substrate Water Quality Stream Length Draft Central Texas Mussels SSA Report 70 April 2018 T AF DR Figure 5.4. Location and current condition for the six current populations of Texas fatmucket in the Colorado and Guadalupe River basins. Draft Central Texas Mussels SSA Report 71 April 2018 5.C.4 CURRENT POPULATION RESILIENCY The Texas fatmucket is known to currently occur in the Colorado and Guadalupe River basins. Currently, there are six known populations across these two basins. The Colorado River basin support five populations of Texas fatmucket with two of the five Colorado populations in moderate condition and the remaining three are unhealthy. The Guadalupe basin contains one known population of Texas fatmucket. This population is currently unhealthy due to low abundance and low evidence of recruitment. 5.C.5 CURRENT SPECIES REPRESENTATION AF T We consider the Texas fatmucket to have representation in the form of genetic and ecological diversity in each of two basins: Colorado and Guadalupe. As discussed in Chapter 2, the genetic structure of these five populations indicates that there is some level of genetic differentiation among populations (Inoue et al. 2018, pp. 4, 10, 13). The Guadalupe basin supports only one population of Texas fatmucket in the upper reaches near Kerrville, Texas. This population shows genetic distinction from other known populations of Texas fatmucket. In fact, ongoing research suggests this population may be a new undescribed species of Lamspilis as it preliminary conclusions suggest it may be genetically distinct from L. bracteata and L. hydiana (Inoue et al. 2018, pp. 10, 13). 5.C.6 CURRENT SPECIES REDUNDANCY DR Within these identified representation areas, the Guadalupe River basin has one current population and therefore exhibits no redundancy. The Colorado River basin has five separate populations and therefore relatively high redundancy within this basin. 5.D TEXAS FAWNSFOOT 5.D.1 CURRENT DISTRIBUTION Texas fawnsfoot occurs in the lower reaches of the Colorado and Brazos Rivers, (Randklev et al. 2017, p. 4), as well as in the main stem of the Trinity River (Figure 5.5). Among these three basins, Texas fawnsfoot currently inhabits 659.7 stream miles of a presumed 3,540.5 stream miles, representing 18.7% of its presumed historical distribution. Draft Central Texas Mussels SSA Report 72 April 2018 T AF DR Figure 5.5. Location of each of the seven current populations of Texas fawnsfoot in the Trinity, Brazos, and Colorado Rivers. Draft Central Texas Mussels SSA Report 73 April 2018 L OWER E AST F ORK OF THE T RINITY R IVER   The East Fork Trinity River population is 11.8 stream miles in length and extends upstream of the Trinity River confluence to roughly the Hwy 187 bridge crossing. This stretch of river is in Kaufman County and extends to the Kaufman and Ellis Counties northeastern border. Randklev et al. (2017b, p. 16) reported finding 40 Texas fawnsfoot in bank and riffle habitats of the Trinity River. The species was more abundant in the middle reaches relative to the other reaches including the East Fork (pp. 10, 16). Additionally, Randklev (2018, p. 1) reported finding 12 live Texas fawnsfoot from the East Fork of the Trinity River among three sites surveyed in 2017. T M IDDLE T RINITY R IVER The Texas fawnsfoot is found in the mainstem Trinity River just upstream of the Hwy 287 crossing downstream to the Madison and Walker counties, for a total of 139.8 stream miles. This section of river flows through Navarro County, Anderson, Leon, Houston, and Madison counties, Texas. AF Texas fawnsfoot appears to have been extirpated from approximately 90% of its historical range in the Trinity Basin (Randklev et al. 2017, p. 11). Randklev et al. (2017) surveyed the Trinity River drainage in 2014-2017 and found that mussel species richness and abundances were “greatest in the middle Trinity near Oakwood, TX, and in the Elm Fork of the Trinity River” although richness and abundance were both reduced immediately downstream of the Dallas-Fort Worth metroplex and Lake Livingston (p. 2). L OWER C LEAR F ORK OF THE B RAZOS R IVER DR This population occurs in the Clear Fork of the Brazos River from near Fort Griffin, at the US Hwy 283 bridge crossing, upstream 12.9 miles to the CR 292 bridge crossing, in Shackelford and Throckmorton counties, Texas. In 2010, HDR Engineering, Inc was contracted to perform 56 mussel surveys throughout the Clear Fork Brazos River basin. In total, one live Texas fawnsfoot, and 264 dead individuals were found. Surveys were conducted in the Clear Fork of the Brazos River, and in several tributary streams (Mulberry, Elm, and Deadman creeks). The only live Texas fawnsfoot was recovered from the Clear Fork Brazos near Fort Griffin (HDR Engineering 2010, pp. 4-6; HDR Engineering 2011, p. 4). Bonner et al. (2018) surveyed the Clear Fork of the Brazos River and in the Brazos River above Possum Kingdom Reservoir basin (p. 15), but report “dead shell material suggesting a once diverse mussel community” possibly resulting from widespread dewatering of the river during the drought years of 201113 (p. 25). No live Texas fawnsfoot were found. Draft Central Texas Mussels SSA Report 74 April 2018 U PPER B RAZOS R IVER The Texas fawnsfoot population in the upper Brazos River extends from the Hwy 180 crossing downstream to Interstate Hwy 20 for a total of 62.2 stream miles, in Palo Pinto and Parker counties, Texas between Possum Kingdom and Granbury Lakes. Bonner et al. (2018, p. 10) found 1 live Texas fawnsfoot in the Brazos River near the CR 281 bridge crossing, and Randklev (2018, p. 1) found a total of 23 live Texas fawnsfoot in the upper Brazos River upstream of Interstate Hwy 20 to approximately the Hwy 180 bridge crossing. M IDDLE /L OWER B RAZOS R IVER AF T This population of Texas fawnsfoot occupies a total of 331.9 miles of the Brazos River mainstem from State Highway 6 crossing (south of the City of Waco) downstream to about two miles south of the Highway 69 crossing near Sugar Land, Texas. This population occurs in McLennan, Falls, Robertson, Milam, Brazos, Burleson, Grimes, Washington, Waller, Austin, and Fort Bend counties, Texas. The population also extends into the lower 14.5 miles of the Navasota River (a Brazos River tributary) in Grimes and Brazos counties, Texas. In total, this population occupies 346.4 stream miles. However, the areas with the greatest known abundances are in the lower Brazos River downstream of the Navasota River confluence. DR In September 2017 biologists from the Service, Texas Department of Transportation (TXDOT), and Texas Parks and Wildlife Department (TPWD) found a total of 28 live Texas fawnsfoot at the FM 413 bridge crossing. These mussels were relocated upstream. In addition, 18 shells were collected with no tissue inside and 24 fresh dead shells (with tissue intact) were found, 12 of these were retained for genetic analysis (Tidwell 2017, entire). These animals were all quite small, suggesting evidence of recent reproduction and recruitment. The animals were found in a shallow area, downstream of an island forming around a bridge pylon in sand and small gravel particles. Several individuals were < 20 mm (total shell length) with evidence of byssal threads for attachment, a characteristic of juvenile mussels. In 2009, Randlev et al. (2010, pp. 297-8) found a population of Texas fawnsfoot in the Brazos River near its confluence with the Navasota River (Grimes and Washington counties, Texas), 8 km southwest of Navasota, Texas, in a reach of the river “characterized by steep banks with extensive riparian vegetation” in a “shallow pool with soft sandy sediment” and report that their finding is “the first record of a population of T. macrodon since its initial description in 1859.” This finding was also reported in Randklev et al. (2010) where the site was described as near SH 105 on the left bank of the river (pp. 17,19, 51). Burlakova and Karatayev (2010) reported collecting 1 Texas fawnsfoot and few recent dead from 27 locations along the Brazos River in 2006-2007 (p. 17). Howells (2010) reported 34 fresh dead Texas fawnsfoot shells were collected from the Brazos River downstream of Highway 21 in Brazos and Burleson Counties, Texas, and that the shells represented “both sexes as well as mixed sizes and ages” (pp. 21-2). Pease et al. (2014) report finding a single subfossil (long dead) was found at the Highway 67 Bridge crossing near Glen Rose, in Somervell County, Texas in 2012 (p. 13). Draft Central Texas Mussels SSA Report 75 April 2018 Randklev et al. (2014) found approximately 188 live Texas fawnsfoot from 29 of 92 sites sampled in the Lower Brazos River from Austin and Fort Bend Counties (pp. 22-37, 44-45), mainly from bank habitats with moderate water depth, slow to moderate flows, and fine firmly compacted sediments (p. 2). Randklev et al. (2017) reported finding 4 live Texas fawnsfoot from 2 of 9 sites in the Little River, near Buckholts in Milam County (p. 139), but not from the San Gabriel River (searched 20 sites) and Brushy Creek (searched 30 sites) in Williamson and Milam counties, Texas (p. 148). Tsakiris and Randklev (2016) report finding 21 live Texas fawnsfoot from 2 sites in the lower portions of Yegua Creek, at the confluence with the Brazos River (pp. 122-3). Further research into the population dynamics of this species and predator/prey interactions with its presumed affiliate host fish, the molluscivorous freshwater drum, may help explain apparently low abundances of the Texas fawnsfoot in the Lower Brazos River. T L OWER S AN S ABA /M IDDLE C OLORADO R IVER AF The population occurs from the CR 340 bridge crossing downstream to the Colorado confluence and for the first one mile the Colorado River downstream of the San Saba River confluence. This population of Texas fawnsfoot has a total stream distance of approximately 43 miles, in San Saba and Mills counties, Texas. DR Howells (2000) reported finding one fresh dead Texas fawnsfoot shell from the Colorado River upstream of State Hwy 16 (and above the confluence with the San Saba River) in Mills and San Saba counties, Texas, and reports it as “the largest specimen reported to date” (56 mm total shell length; pp. 25-6). Sowards et al. (2013) reported finding three live individuals from a series of run-riffle-pool habitats in the San Saba River, east of the City of San Saba, in July 2012 (pp. 64-5). Tsakiris and Randklev (2014, p. 11) reported finding 7 live Texas fawnsfoot from two locations on the San Saba River (at the CR 340 and CR 126 bridge crossings). Most recently, in 2017, Randklev et al. (2017) reported surveying the San Saba River, and no live Texas fawnsfoot or shells were found (p. 135). L OWER C OLORADO R IVER This Texas fawnsfoot population stretches for a 108.6-mile river area. Texas fawnsfoot are known to occur from about 9 river miles upstream of the US Hwy 71 crossing west of Columbus, Texas, downstream approximately to the Texas State Highway 35 crossing east of Bay City, Texas. The population occurs in Colorado, Wharton, and Matagorda Counties. Burlakova and Karatayev (2010) reported collecting 52 Texas fawnsfoot “on a sandy shore of the Colorado River”, near Garwood in Colorado County in April 2009 (p. 17). Near that location in 2013, Service biologists found 4 gravid females during two surveys near the same site (FM 950 crossing) in the vicinity of Garwood, Texas. Service biologists found ten live Texas fawnsfoot during a survey at approximately this same location in 2016. In 2015, Service biologists found over 10 Texas fawnsfoot and fresh dead shells in bank habitats and shallow water in the Colorado River near Lane City in Wharton Draft Central Texas Mussels SSA Report 76 April 2018 County, Texas. Most recently, Bonner et al. (2018) found 9 live Texas fawnsfoot from 7 sites in the Lower Colorado River basin (p. 28), from Colorado County to Matagorda County (p. 21). 5.D.2 AREAS PRESUMED EXTIRPATED Texas fawnsfoot was historically distributed throughout the Colorado and Brazos basins (Howells 2014, p. 111-2; and reviewed in Randklev et al. 2017c, pp. 136-7) and in the Trinity basin (Randklev et al. 2017b, p. 11). Texas fawnsfoot historically occurred in the Leon River (Brazos Basin) but is now absent (Popejoy et al. 2016, p. 477). Randklev et al. (2017c, p. 135) surveyed for Texas fawnsfoot in the Llano, San Saba, and Pedernales rivers and found no individuals or dead shell material. T 5.D.3 CURRENT CONDITIONS DR AF To summarize the overall current conditions of Texas fawnsfoot populations, we sorted them into three categories (healthy, moderately healthy, and unhealthy) based on the population factors and habitat elements discussed in Chapter 3 and displayed in Table 5.6. Table 5.7 shows the overall condition of Texas fawnsfoot populations, as displayed in Figure 5.6. Draft Central Texas Mussels SSA Report 77 April 2018 Table 5.6. Population and habitat characteristics of Texas fawnsfoot populations used to create condition categories in Table 5.7. Habitat Factors Population Factors Condition Abundance Reproduction Substrate Flowing Water Found in nearly all available habitats surveyed. More than 100 individuals found per population survey. 50% or more sites with juveniles (< 35 mm) and gravid females present during the breeding season and fish hosts present. Clay, mud, and sandbanks present. Streambanks stable and erosion not documented. Flowing water present yearround and sufficient to maintain water quality. No recorded periods of zero flow days. No documentation of dewatered habitats. No known incidence of contaminant spills, low dissolved oxygen, or evidence of exposure extreme high or low temperatures Clay, mud, and sand banks present. Streambanks mostly stable with some erosion/scouring. Flowing water present yearround, but water levels approaching low levels. No instance of zero flow days and stream bank drying deviates from appropriate hydrology, with limited habitat desiccation. Contaminants known, low dissolved oxygen and temperature extremes documented. Levels not high enough to risk extirpation. > 50 river miles Moderately Healthy Found in approx. 50% of all available habitats surveyed. 49-20 river miles Between 26 – 99 individuals found per population survey. 25-50% of sites inhabited by juveniles (< 35 mm) and gravid females present during the breeding season and fish hosts present in moderate abundance. DR Healthy Unhealthy Extirpated/ Func. Extirpated < 19 river miles none Water Quality AF T Occupied Habitat Found in few areas of suitable habitat. Between 2 – 25 individuals found per population survey. < 25% of sites inhabited by juveniles (< 35 mm) and gravid females present during the breeding season and fish host present in low abundance and/or ability to disperse is reduced. Stream unstable and erosion occurring during high flow. Suitable substrate limited to isolated locations. Flowing water does not persist annually. Stream banks documented to dry during low flow. Habitat dewatering occurs somewhat regularly. Very few or no live individuals documented during surveys (< 1). No evidence suggesting that juveniles or gravid females are present. Fish host not known to occur. No suitable habitat present. Dry stream bed or zero flow Water quality degradation such days high enough to preclude that occupancy of otherwise survival. suitable habitat is precluded. Draft Central Texas Mussels SSA Report 78 Known exposure to contaminants, low dissolved oxygen, and documented cases of excessive water temperatures extremes. Water quality parameters diminished such that exposure threatens mussel survival. April 2018 Table 5.7. Current condition of Texas fawnsfoot populations. Texas Fawnsfoot Population Factors Brazos Colorado Population Abundance Reproduction Habitat Factors Flowing Water Substrate Water Quality Overall Condition Clear Fork Brazos Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Upper Brazos Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Lower Brazos Healthy Moderate Moderate Moderate Healthy Moderate Moderate Lower San Saba Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Lower Colorado Healthy Moderate Healthy Moderate Moderate Moderate Moderate East Fork Trinity Unhealthy Moderate Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Moderate Unhealthy Moderate Moderate Moderate Unhealthy DR Trinity AF T Basin Stream Length Draft Central Texas Mussels SSA Report 79 April 2018 T AF DR Figure 5.6. Location and current condition of the seven populations of the Texas fawnsfoot in the Trinity, Brazos, and Colorado River basins. Draft Central Texas Mussels SSA Report 80 April 2018 5.D.4 CURRENT POPULATION RESILIENCY The Texas fawnsfoot is known to occur in three river basins: the Trinity, Brazos, and Colorado. The species has a total of seven populations spread across these three basins. In the Trinity River basin, two populations are currently isolated from one another and are an unhealthy condition. The Trinity River populations both exhibit low resiliency. The Brazos River contains three populations of Texas fawnsfoot: the Clear Fork Brazos, upper Brazos, and lower Brazos River populations. Prior to dam construction, these populations were likely all once connected, but now they are isolated from one another. Two of the populations are in unhealthy condition and one is moderately healthy. The Colorado basin contains two isolated populations of Texas fawnsfoot. The lower Colorado population is currently moderately healthy and has a relatively large geographic area. The San Saba River population is unhealthy and therefore has low resiliency. T 5.D.5 CURRENT SPECIES REPRESENTATION AF We consider the Texas fawnsfoot to have representation in each of three river basins: the Trinity, Brazos, and Colorado River basins (Figure 5.6) 5.D.6 CURRENT SPECIES REDUNDANCY Within these identified representation areas, Texas fawnsfoot is known from two populations in the Trinity River basin, three in the Brazos River basin, and two in the Colorado River basin. 5.E TEXAS PIMPLEBACK DR 5.E.1 CURRENT CONDITION Texas pimpleback is known from the Guadalupe and Colorado River basins. This species has undergone several taxonomic changes and current research suggests the species could be split again into C. petrina and a new yet undescribed species of Cyclonaias (Chapter 2). This species currently occupies 27.6% of its presumed historical range. The Texas pimpleback currently is found in a combined 572 river miles of a presumed historical range of 2,073.6 stream miles. Draft Central Texas Mussels SSA Report 81 April 2018 T AF DR Figure 5.7 Location of each of the seven current populations of Texas pimpleback in the Colorado and Guadalupe River basins. Draft Central Texas Mussels SSA Report 82 April 2018 L OWER C ONCHO R IVER This population extends for 14.1 stream miles from the FM 381 bridge crossing to the US Hwy 83 bridge crossing near Paint Rock and entirely within Concho County, Texas. This population of Texas pimpleback appears to be very small, if not already extirpated, and apparently consists entirely of only large, old individuals; evidence of a population that is not reproducing and recruiting new cohorts. T Burlakova and Karatayev (2010) reported collecting 47 live Texas pimpleback in July-August 2008 and stated that this population was probably the only large remaining population of the species and that the population did not appear to be reproducing (p. 11). This population experienced very low flows during the 2011-12 drought (Burlakova and Kratayev 2010, pp. 101-1), and very few live individuals have been found since that drought (Blair 2018, p. 1). The population was apparently experiencing a lack of recruitment prior to the drought, and the drought appeared to have likely eliminated the adults. The North Concho River frequently goes dry during the summer, and streamflows were “at or below normal during all of 2011, except for a brief period of storm runoff in August 2011” (USGS 2013, pp. 13, 18). AF At another site in the Concho River, Howells (2000, p. 23) reported finding dead shells of Texas pimpleback in abundance in Concho County, Texas, where the flow had been so reduced such that only isolated pools remained watered. Similarly, Howells (2000, p. 23) reported finding dead shells of Texas pimpleback from the Paint Rock City Park, in a dry reach of the Concho River with only isolated pools. Blair (2018, entire) reported searching for and finding only one live Texas pimpleback in the Concho River near Paint Rock in 2012. During multiple surveys by other researchers in 2013, and 2016 no live Texas pimplebacks were recorded. This apparent lack of any small animals, alive or dead shell, suggests that population is functionally, if not actually, extirpated. DR U PPER S AN S ABA R IVER   This population extends for 29.6 stream miles from the FM 864 bridge crossing downstream to the RR 2092 bridge crossing in Menard County, Texas. Service biologists collected fresh dead shells from the San Saba River near Menard, Texas, in 2013. Randklev et al. (2017, p. 108) found one live Texas pimpleback from a riffle near Menard, Texas in 2017. L OWER S AN S ABA AND M IDDLE C OLORADO R IVER The Texas pimpleback population occurs in the lower 41.9 miles of the San Saba River, from the CR 340 crossing downstream to the Colorado River confluence. The population occurs in the Colorado River from the FM 503 crossing (downstream of lake O.H. Ivie) to the Hwy 190 crossing just downstream of the Colorado-San Saba River confluence for a total Colorado River population of 136.5 miles. In total, this population is 178.4 stream miles long and is in San Saba, McCulloch, Mills, Brown, and Coleman counties, Texas. Draft Central Texas Mussels SSA Report 83 April 2018 Howells (2000, pp. 25-6) found 3 fresh dead Texas pimpleback shells from the Colorado River upstream of SH-16 above the confluence with the San Saba River, in Mills and San Saba Counties, Texas. Similarly, in 2011, three live individuals were found in the Colorado River downstream of CR 266 (Randklev 2018, p. 1.). In 2012, 21 live Texas pimpleback were found from 4 different sites in the San Saba River in San Saba County Texas, and in 2013, 15 live animals were found from the San Saba River in San Saba County, Texas (Braun et al. p. 14-15). Sowards et al. (2013) reported finding 247 live individuals from a series of run-riffle-pool habitats in the San Saba River, east of the City of San Saba, in July 2012 (pp. 64-5), and Tsakiris and Randklev (2014, p. 11) reported finding 481 live Texas pimplebacks from two locations (CR 340 and CR 126 bridge crossings) in the San Saba River. T In 2017, Service biologists found 15 live Texas pimpleback during surveys in San Saba County (CR 340) crossing (USFWS 2017, p. 6) and 5 live Texas pimpleback from the San Saba River near San Saba, Texas (USFWS 2017, p. 9). L LANO R IVER AF Bonner et al. (2018) reported finding 97 live Texas pimpleback from 6 sites in the “Middle Colorado River” basin, defined as from O.H. Ivie Reservoir to Lake Buchanan (pp. 6, 29), with the majority of occurrences in San Saba County, below the San Saba River confluence (p. 19), and reported new observations of five live individuals below O.H. Ivie Reservoir in Coleman County, Texas (p. 22). DR The Llano River population of Texas pimpleback occupies only 4.9 miles of the Llano River from FM 1871 downstream to the RR 2389 bridge crossing in Mason County. Mussel populations in this area including Texas pimpleback see considerable scientific and research collection activities due to its ease of access and proximate location to major cities. Sowards et al. (2012) report finding 10 live Texas pimpleback from the FM1871 bridge crossing of the Llano River in Mason County, Texas, from “gravel deposits containing macrophytes” (p. 4). In 2016 Service biologists found one live Texas pimpleback from one site near Mason, Texas during a reconnaissance survey. Biologists noted the presence of several old shells including one that had been tagged (unknown source) in an apparent previous study. Additionally, in 2016 Service biologists found eight live Texas pimpleback from one site near Mason, Texas during a reconnaissance survey. Biologists noted the presence of multiple size classes (26-55 mm total length) indicating possible recent recruitment. Randklev et al. (2017) report finding 23 live Texas pimpleback from 3 sites on the Llano River, near Mason, Texas, upstream of the confluence with the James River, in pool and pool/run habitats, and note some evidence of recruitment (p. 108). BIO-WEST, Inc. (2018) report finding and relocating 1 Texas pimpleback from Llano Park Lake on the Llano River near the City of Llano in Llano County, Texas, during a reservoir drawdown and dewatering event that took place in November and December of 2017 (pp. 2-3). Draft Central Texas Mussels SSA Report 84 April 2018 L OWER C OLORADO R IVER The Texas pimpleback is known to occur currently in the lower Colorado River from about 9 miles upstream of the US Hwy 71 crossing (near Columbus, Texas) downstream to Jarvis Creek confluence (southeast of Lane City). In total, this population occupies 98.2 stream miles in Colorado and Wharton counties, Texas. In 2014, the Service located forty-nine (49) live Texas pimpleback during a survey at a long-term monitoring site near FM 950 bridge crossing in Garwood. In 2015, Service biologists found three (3) live animals at a long-term monitoring site and LCRA pumping station both sites were near Lane City, in Wharton County, Texas (USFWS 2016, entire). AF U PPER G UADALUPE R IVER T Bonner et al. (2018) report searching for, and finding, 30 live Texas pimpleback from 6 sites in the “Lower Colorado River” basin, defined as from Longhorn Dam to Bay City Dam (pp. 6, 28), with the occurrences being from Colorado County (above Columbus) to Wharton County (near Wharton, p. 19). DR This population of Texas pimpleback occurs from approximately the origination of the Guadalupe River (confluence of the North and South Fork Guadalupe Rivers) downstream to the Guadalupe River State Park, above Canyon Lake. In total, this population occupies 88.4 stream miles in Kerr, Kendall, and Comal counties, Texas. In 2013, Service biologists located 1 live Texas pimpleback below the UGRA dam on the Guadalupe River in Kerr County, Texas (Braun et al. 2012, pp. 14-15). In 2018, Bonner et al. (2018) reported finding 10 live Texas pimpleback from 2 sites in the Upper Guadalupe River between Hunt and Center Point, in Kerr County, Texas (pp. 19, 31). Inoue (2018, entire) searched for and found 10 living Texas pimpleback near the Ehlers Road crossing of the Guadalupe River, near Comfort, Texas. L OWER G UADALUPE R IVER In the lower section of the Guadalupe River, the Texas pimpleback occupies a total of 41.8 stream miles in the San Marcos River (a tributary to the Guadalupe River) from the US Hwy 90 crossing near Luling, Texas, downstream to the Guadalupe River confluence. Continuing downstream of the San Marcos River confluence the populations extends 116.5 miles to approximately the US 77 crossing. This population is the largest and most robust of any Texas pimpleback and is in Caldwell, Guadalupe, Gonzales, DeWitt, and Victoria counties, Texas. In 2012, Service biologists encountered one (1) live individual near the Hwy 77 crossing in Victoria County, and in 2013, Service biologists located 7 live Texas pimpleback and several fresh dead shells at Highway 77 near Victoria, Texas on the Guadalupe River in Victoria County, Texas (Braun et al. 2012, pp. 14-15). Tsakiris and Randklev (2016) observed a total of 893 Texas pimpleback, out of a total of over 21,000 mussels, during a comprehensive survey effort of the Lower Guadalupe River in 2014-15 (p. 13) and individuals were found in all survey locations between Gonzalez and Victoria, Texas, but only in riffle Draft Central Texas Mussels SSA Report 85 April 2018 habitats. Randklev et al. (2017) reported finding 41 live Texas pimpleback from 8 of 13 sites surveyed in the Lower Guadalupe River, between Cuero and Victoria, Texas (p. 111) but note that persistent high flows precluded access to riffle habitats, which are known to be the “optimal mesohabitat for the species” (p. 108). 5.E.2 AREAS PRESUMED EXTIRPATED Texas pimpleback was historically distributed throughout the Colorado and Guadalupe basins (Howells 2014, p. 93-4; reviewed in Randklev et al. 2017, pp. 109-10). The species is likely extirpated from the Pedernales River (Randklev et al. 2017, p. 108), and from the San Marcos River where one long dead individual was found in 2010 (Wilkins et al. 2011, p. 3) T 5.E.3 CURRENT CONDITIONS OF TEXAS PIMPLEBACK DR AF To summarize the overall current conditions of Texas pimpleback populations, we sorted them into three categories (healthy, moderately healthy, and unhealthy) based on the population factors and habitat elements discussed in Chapter 3 and displayed in Table 5.8. Table 5.9 shows the overall conditions of Texas fatmucket populations, as displayed in Figure 5.7. Draft Central Texas Mussels SSA Report 86 April 2018 Table 5.8. Population and habitat characteristics of Texas pimpleback populations used to inform condition categories in Table 5.9. Habitat Factors Population Factors Occupied Habitat Healthy Unhealthy Reproduction Substrate > 50 river miles Found in nearly all available habitats surveyed. More than 100 individuals found per population survey. 50% or more sites with juveniles (< 35 mm) and gravid females present during the breeding season and fish hosts present. Riffle and crevice habitat present. Gravel and cobble substrate sufficient to provide lodging. Flowing water present yearround and sufficient to maintain temperature and dissolved oxygen. No recorded periods of zero flow days. No documented habitat exposure. No known incidence of contaminant spills, low dissolved oxygen, or evidence of exposure extreme high or low temperatures 49 - 20 river miles Found in approx. half all available habitats surveyed. Between 26 – 99 individuals found per population survey. 25-50% of sites inhabited by juveniles (< 35 mm) and gravid females present during the breeding season and fish hosts present in moderate abundance. Riffle and crevice habitat present. Gravel and cobble substrate sufficient to provide lodging with some sediment deposition. Flowing water present yearround, but water levels approaching low levels. No instances of zero flow days and riffle dewatering not documented. Contaminants known, low dissolved oxygen and temperature extremes documented. Levels not high enough to risk extirpation. DR Moderately Healthy Abundance Extirpated/ Functionally Extirpated Flowing Water Water Quality AF T Condition < 19 river miles < 25% of sites inhabited by juveniles (< 35 mm) and Found in few areas gravid females present during the breeding season of suitable habitat. and fish host present in Between 2 – 25 individual found per low abundance and/or ability to disperse is population survey. reduced. none Very few or none documented during surveys (< 1). Draft Central Texas Mussels SSA Report No evidence suggesting that juveniles or gravid females are present. Fish host not known to occur. Riffles eroded or upstream sediments Zero flow days or riffle deposited at high dewatering documented enough level to preclude within previous decade. inhabitation. No suitable habitat present. 87 Known exposure to contaminants, low dissolved oxygen, and documented cases of excessive water temperatures extremes. Water quality parameters diminished such that exposure threatens mussel survival. Dry stream bed or zero flow Water quality degradation such days high enough to preclude that occupancy of otherwise survival. suitable habitat is precluded. April 2018 Table 5.9. Current condition of Texas pimpleback populations. Texas Pimpleback Population Factors Population Overall Condition Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Colorado & San Saba Healthy Healthy Unhealthy Moderate Moderate Moderate Moderate Upper San Saba Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Llano Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Healthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Healthy Moderate Moderate Moderate Moderate Moderate Concho Colorado Abundance Reproduction Habitat Factors Flowing Water Substrate Water Quality Lower Colorado DR Upper Guadalupe Guadalupe San Marcos & Lower Guadalupe AF T Basin Stream Length Draft Central Texas Mussels SSA Report 88 April 2018 T AF DR Figure 5.8. Location and overall current population condition for all seven populations of Texas pimpleback in the Guadalupe and Colorado River basins. Draft Central Texas Mussels SSA Report 89 April 2018 5.E.4 CURRENT POPULATION RESILIENCY The Texas pimpleback is known to currently occur in the Colorado and Guadalupe River basins. Currently, there are seven known populations across these two basins. The Colorado River basin supports four populations of Texas pimpleback. Three of these populations are currently unhealthy while the largest population is in moderate condition. The San Saba and middle Colorado population is the most robust and would be most resilient against stochastic events, such as floods. The Guadalupe basin has two populations: one in unhealthy condition in the upper reaches of the river and one in moderate condition in the lower, which also extends into the San Marcos River. T 5.E.5 CURRENT SPECIES REPRESENTATION AF We consider the Texas pimpleback to have representation in each river basin: the Colorado and Guadalupe River basins (Figure 5.8). Current research indicates that all the known Texas pimpleback in the Guadalupe River basin are actually a cryptic, yet undescribed species of Cyclonaias (Randklev et al. 2017c, p. 273). If preliminary findings are substantiated, Texas pimpleback would have representation in only one basin, the Colorado. 5.E.12 CURRENT SPECIES REDUNDANCY Within these identified representation areas, the Texas pimpleback has five populations in the Colorado River basin, one population in the Guadalupe River basin. SUMMARY OF CURRENT CONDITIONS OF CENTRAL TEXAS MUSSELS DR 5.F All four species of Central Texas mussels exhibit various levels of resiliency, redundancy, and representation across the major river basins in which they occur. However, no population seems to contain all of the necessary habitat and population factors necessary to warrant a strong, healthy mussel population. Given our analysis of current condition, none of the species were considered to be in healthy condition overall. While some species have aspects, or factors, that are healthy (such as stream length, or abundance) none of the species has all of the factors necessary to support a highly resilient population. Draft Central Texas Mussels SSA Report 90 April 2018 CHAPTER 6 ‐ FACTORS INFLUENCING VIABILITY This chapter evaluates the past, current, and future factors that may affect Central Texas mussel populations and influence the needs for long-term species viability. Each of these factors is explored in the “Cause and Effects Tables” appended to this report as Appendix B. The Cause and Effects Tables analyze, in detail, the pathways by which each factor influences a population and species. Further, each of the causes is examined for its historical, current, and potential future effects on the species’ status. These factors include: (1) increased fine sediment, (2) changes in water quality, (3) altered hydrology in the form on inundation, (4) altered hydrology in the form of loss of flow and scour of substrate, (5) predation and collection and (6) barriers to fish movement. AF 6.A.1 INCREASED FINE SEDIMENT T Current and potential future effects, along with current expected distribution and abundance, determine present viability and, therefore, vulnerability to extinction. We organized these influences around the stressors (i.e., changes in the resources needed by each species) and discuss the sources of those stressors. For more information about each of these influences, see Appendix B. Those risks that are not known to have effects on Central Texas mussel populations are not discussed in this SSA report. DR Juvenile and adult Central Texas mussels inhabit microsites that have abundant interstitial spaces, or small openings in an otherwise closed matrix of substrate, created by gravel, cobble, boulders, bedrock crevices, tree roots, and other vegetation, with some amount of fine sediment (i.e., clay and silt) necessary to provide appropriate shelter. However, excessive amounts of fine sediments can reduce the number of appropriate microsites in an otherwise suitable mussel bed by filling in these interstitial spaces, and can smother mussels in place. Central Texas mussels generally require stable substrates, and loose silt deposits do not generally provide for substrate stability. Interstitial spaces provide essential habitat for juvenile mussels. Juvenile freshwater mussels burrow into interstitial substrates, making them particularly susceptible to degradation of this habitat feature. When clogged with sand or silt, interstitial flow rates and spaces may become reduced (Brim Box and Mossa 1999, p. 100), thus reducing juvenile habitat availability. Under a natural flow regime, a river or stream is in equilibrium in the context of sediment load, such that as sediments are naturally washed away from one microsite to another such that the amount of sediment in the substrate is relatively stable, given that different reaches within a river or stream may be aggrading or degrading sediment (Poff et al. 1997, pp. 770-2). Fine sediments collect on the streambed and in crevices during low flow events, and much of the sediment is washed downstream during high flow events (also known as cleansing flows). However, increased frequency of low flow events (from groundwater extraction, instream surface flow diversions, and drought) combined with a decrease in cleansing flows (from reservoir management and drought) causes sediment to accumulate. When water velocity decreases, which can occur from reduced streamflow or inundation, water loses its ability to carry sediment in suspension; sediment falls to the substrate, eventually smothering mussels not adapted to soft substrates (Watters 2000, p. 263). Sediment accumulation can be exacerbated when there is a simultaneous increase in the sources of fine sediments in a watershed. In the range of the Central Texas mussels, these sources include streambank erosion from development, agricultural activities, livestock Draft Central Texas Mussels SSA Report 91 April 2018 and wildlife grazing and browsing, in-channel disturbances, roads, and crossings, among others (Poff et al. 1997, p. 773). 6.A.2 CHANGES IN WATER QUALITY T Water quality can be impaired through contamination or alteration of water chemistry. Chemical contaminants are ubiquitous throughout the environment and are a major reason for the current declining status of freshwater mussel species nationwide (Augspurger et al. 2007, p. 2025). Chemicals enter the environment through both point and nonpoint discharges, including spills, industrial sources, municipal effluents, and agricultural runoff. These sources contribute organic compounds, heavy metals, pesticides, herbicides, and a wide variety of newly emerging contaminants to the aquatic environment. Ammonia is of particular concern below water treatment plants because freshwater mussels have been shown to be particularly sensitive to increased ammonia levels (Augspurger et al. 2003, p. 2569). It is likely for this reason that Central Texas mussels are not known to be found for many miles downstream of wastewater treatment plants. Elevated concentrations of un-ionized ammonia ( > 0.2 ppb) has been implicated in the reproductive failure of other freshwater mussel populations (Strayer and Malcom 2012, pp. 1787-8). DR AF An additional type of water quality impairment is an alteration of water quality parameters such as dissolved oxygen, temperature, and salinity levels. Dissolved oxygen levels may be reduced from increased nutrients in the water column from runoff or wastewater effluent, and juveniles seem to be particularly sensitive to low dissolved oxygen (Sparks and Strayer 1998, pp. 132–133). Increased water temperature from climate change and from low flows during drought can exacerbate low dissolved oxygen levels as well as have its own effects on both juvenile and adult mussels. Finally, high salinity concentrations are an additional concern in certain watersheds, where dissolved salts can be particularly limiting to Central Texas Mussels. Upper portions of the Brazos and Colorado Rivers, originating from the Texas High Plains, contain saline water, sourced from both natural geological formations, and from oil and gas development. Salinity in river water is diluted by surface flow and as surface flow decreases the salt concentrations increase, having adverse effects on freshwater mussels. Even low levels of salinity (2-4 ppt) have been demonstrated to have substantial negative effects on reproductive success, metabolic rates, and survival of freshwater mussels (Blakeslee et al. 2013, p. 2853). Contaminant spills are also of concern. Reductions in surface flow from drought, instream diversion, and groundwater extraction concentrates contaminant and salinity levels and increases water temperatures in streams and exacerbates effects to Central Texas mussels. 6.A.3 ALTERED HYDROLOGY ‐ INUNDATION Central Texas Mussels are adapted to flowing water (lotic habitats) rather than standing water (lentic habitats) and require free-flowing water to survive. Low flow events (including stream drying) and inundation can eliminate appropriate habitat for Central Texas Mussels, and while these species can survive these events for a very short duration, populations that experience prolonged drying events or repeated drying events will not persist. Inundation has primarily occurred upstream of dams, both large (such as the Highland Lakes and other major flood control and water supply reservoirs) and small (low water crossings and diversion dams typical of the tributaries and occurring usually on privately owned lands). Inundation causes an increase Draft Central Texas Mussels SSA Report 92 April 2018 in sediment deposition, eliminating the crevices that many Central Texas mussel species inhabit. In large reservoirs, deep water is very cold and often devoid of oxygen and necessary nutrients. Cold water (less than 11 °Celsius (C) (52 °Fahrenheit (F))) has been shown to stunt mussel growth and delay or hinder spawning. The Central Texas mussels are not known to tolerate inundation under large reservoirs. Further, deep water reservoirs with bottom release (like Canyon Reservoir, which supports a recreational trout fishery) can affect water temperatures several miles downriver. AF T The construction of dams, and inundation of reservoirs, and management of water releases have significant effects on the natural hydrology of a river or stream. For example, dams trap sediment in reservoirs and managed releases typically do not conform to the natural flow regime (i.e., higher baseflows, and peak flows of reduced intensity but longer duration). Rivers transport not only water but also sediment, which is transported mostly as suspended load (held by the water column), increases as a power function (greater than linear) of flow, and most sediment transport occurs during floods (Kondolf 1997, p.533). It follows that increased severity of flooding would result in greater sediment transport, with important effects on substrate stability and benthic habitats for freshwater mussels, and other organisms dependent on stable benthic habitats. Further, water released by dams is usually clear and does not carry a sediment load, and is considered “hungry water because the excess energy is typically expended on erosion of the channel bed and banks…resulting in incision (downcutting of the bed) and coarsening of the bed material until a new equilibrium is reached” (Kondolf 1997, p.535). Conversely, depending on how dam releases are conducted, reduced flood peaks can lead to accumulations of fine sediment in the river bed (i.e., loss of flushing flows, Kondolf 1997, pp. 535, 548). DR Operation of flood-control, water-supply and recreation reservoirs results in altered hydrologic regimes, including an attenuation of both high- and low-flow events. Flood control dams store flood waters and then release them in a controlled manner, this extended release of flood waters can result in significant scour, and loss of substrates that provide mussel habitat. Along with this change in the flow of water, sediment dynamics are affected as sediment is trapped above and scoured below major impoundments. These changes in water and sediment transport have negatively affected freshwater mussels and their habitats. 6.A.4 ALTERED HYDROLOGY – FLOW LOSS AND SCOUR Very low water levels are detrimental to Central Texas mussel populations as well. Droughts that have occurred in the recent past have led to extremely low flows in several Central Texas Rivers. Many of these rivers have some resiliency to drought because they are spring fed (Colorado tributaries, Guadalupe), are very large (lower Brazos and Colorado), or have significant return flows (Trinity) but drought in combination with increased groundwater pumping and regulated reservoir releases may lead to lower river flows of longer duration than have been recorded in the past. Streamflow in the Colorado River above the Highland Lakes and downstream of the confluence with Concho River has been declining since the 1960s (as evidenced by annual daily mean streamflow; USGS 2008, pp. 812, 814, 848, 870, 878, 880), and overall river discharge for each of the rivers can be expected to continue to decline due to increased drought as a result of climate change, absent significant return flows (less reuse). There are a few exceptions including the Llano River at Llano (USGS 2008, p. 892), Pedernales River at Fredericksburg (USGS 2008, p. 896), Onion Creek near Driftwood and Onion Creek at Highway 183 (flows appear to become more erratic, characteristic of a developing watershed; USGS Draft Central Texas Mussels SSA Report 93 April 2018 2008, pp. 930, 946). In the San Saba River, continuing or increasing surface and alluvial water withdrawals in combination with drought is likely to result in reduced streamflow in the future. Similarly, flows have declined in the upper Brazos (USGS 2008, pp. 578, 600, 626, 638, 644, 652) and in the middle Brazos, dams have reduced the magnitude of floods (USGS 2008, pp. 676, 754), while flows in the lower Brazos appear relatively unchanged (USGS 2008, p. 766, 776). Flows have declined in the upper Guadalupe (USGS 2008, pp. 992, 994, 1000, 1018) but appear relatively unchanged at Comfort and Spring Branch and in the San Marcos River (USGS 2008, pp. 1004, 1006, 1022), and in the lower Guadalupe River (USGS 2008, pp. 1036, 1040). In the lower sections of the Colorado River, lower flows and reduced high flow events are more common now decades after major reservoirs were constructed (USGS 2008, pp. 964, 966). In the Trinity River, low flows are higher than they were in the past (USGS 2008, pp. 370, 398, 400, 430) because of substantial return flows from Dallas area wastewater treatment plants. DR AF T Many of the tributary streams (i.e., Concho, San Saba, Llano, Pedernales Rivers) historically received significant groundwater inputs from multiple springs associated with the Edwards and other aquifers. As spring flows decline due to drought or groundwater lowering from pumping, habitat for Central Texas Mussels in the tributary streams is reduced and could eventually cease to exist. While Central Texas Mussels may survive short periods of low flow, as low flows persist, mussels face oxygen deprivation, increased water temperature, and, ultimately, stranding, reducing survivorship, reproduction, and recruitment in the population. High-flow events lead to increased risk of physical removal, transport, and burial (entrainment) as unstable substrates are transported downstream by flood waters and later redeposited in locations that may not be suitable. Low-flow events lead to increased risk of desiccation (physical stranding and drying) and exposure to elevated water temperature and other water quality impairments, such as contaminants, as well as to predation. For example, sections of the San Saba River, downstream of Menard, Texas, experienced very low flows during the summer of 2015, which lead to dewatering of occupied habitats as evidenced by observations of recent dead shell material of Texas pimpleback and Texas fatmucket (Geeslin et al. 2015, pp. 2-3). Service, TPWD and TxDOT biologists noted in 2017 that at one site on the Brazos River near Highbank, Texas, the presence of 42 recent dead to fresh dead (with tissue intact) Texas fawnsfoot mussels that likely died as a result of recent drought or scouring events (Tidewell 2017, entire). Conversely, Bonner et al. 2018 noted that a habitat suitability and mussel mark and recapture study site in the lower Colorado River near Altair, Texas suffered significant changes in both mussel community structure and bathymetry during extensive flooding in August 2017, as a result of Hurricane Harvey (p. 266). This study site was selected as it previously held the highest mussel abundance (pp. 242-3) and represented high quality habitat within the Colorado basin, pre flooding events. Survey results indicated a significant decrease in mussel abundance on the scale of nearly two orders of magnitude (p. 266). This location had two of the Central Texas mussels (Texas fawnsfoot and Texas pimpleback) present during initial surveys in 2017 and another candidate species (Smooth pimpleback) that is pending review (p. 242). The distribution of mussel communities and their habitats is affected by large floods returning at least once during the typical life span of an individual mussel (generally from 3 to 30 years), as mediated by the presence of flow refuges, where shear stress is relatively low and where sediments are relatively stable, and “must either tolerate high-frequency disturbances or be eliminated, and can colonize areas that are infrequently disturbed between events” (Strayer 1999, pp. 468-9). Shear stress and relative substrate Draft Central Texas Mussels SSA Report 94 April 2018 stability (RSS) are limiting to mussel abundance and species richness (Randklev et al. 2017a, p. 7) and riffle habitats may be more resilient to high flow events than littoral (bank) habitats. T The Central Texas mussels have historically and are today exposed to extreme hydrological conditions, including severe drought leading to dewatering, and heavy rains leading to damaging scour events and movement of mussels and substrate. The usual drought/flood cycle in Central Texas can be characterized by long periods of time absent of rain interrupted by short periods of heavy rain, resulting in flooding. These same patterns led to the development of flood control and storage reservoirs throughout Texas in the twentieth century. Howells (2000) provides a summary of drought conditions in Texas from 1995-9, characterized by prolonged drought conditions punctuated by severe floods, and their impacts on native unionids and reports that “although no sampling efforts were mounted to document [the] impact on rare endemic unionids, species like...Texas pimpleback, Texas fatmucket, and Texas fawnsfoot were almost certainly reduced in numbers, especially at sites that dried completely” (p.ii). It follows that given the extreme and variable climate of Central Texas; mussels must have life history strategies, and other adaptations, that allow them to persist by withstanding severe conditions, and/or repopulating during more favorable conditions. However, it is also likely that there is a limit to how the mussels might respond to increasing variability, frequency, and severity of extreme weather events. AF Sand and gravel can be mined from rivers or from adjacent alluvial deposits, and instream gravels often require less processing and are thus more attractive from a business perspective (Kondolf 1997, p. 541). Instream mining directly affects river habitats, and can indirectly affect river habitats through channel incision, bed coarsening, and lateral channel instability (Kondolf 1997, p. 541). Excavation of pits in or near to the channel can create a nickpoint, which can contribute to erosion (and mobilization of substrate) associated with head cutting (Kondolf 1997, p. 541). Off-channel mining of floodplain pits can become involved during floods, such that the pits become hydrologically connected, and thus can affect sediment dynamics in the stream or river (Kondolf 1997, p. 545). DR 6.A.5 PREDATION, COLLECTION, DISEASE, AND INVASIVE SPECIES Predation on freshwater mussels is a natural ecological interaction. Raccoons, snapping turtles, and fish are known to prey upon Central Texas mussels. Under natural conditions, the level of predation occurring within Central Texas mussel populations is not likely to pose a significant risk to any given population. However, during periods of low flow, terrestrial predators have increased access to portions of the river that are otherwise too deep under normal flow conditions. High levels of predation during drought have been observed on the Llano and San Saba rivers. As drought and low flow are predicted to occur more often and for longer periods due to the effects of future climate change, the Hill Country tributaries (of the Colorado River) in particular are expected to experience additional predation pressure into the future, and this may become especially problematic in the Llano and San Saba Rivers. Predation is expected to be less of a problem for the lower portions of the main stem river populations, as the rivers are significantly larger than the tributary streams and Central Texas mussels are thus are less likely to be found in exposed or very shallow habitats. Certain mussel beds within some populations, due to ease of access, are vulnerable to over-collection and vandalism. These areas, primarily on the Llano and San Saba Rivers, have well known and well documented mussel beds that are often sampled multiple times annually by various researchers for various scientific projects. Given the additional stressors aforementioned in this chapter, these Draft Central Texas Mussels SSA Report 95 April 2018 populations are being put at additional risk due to over collection and over harvest for scientific needs. Service biologists recently hosted what is planned to be an annual mussel research and coordination meeting to help adaptively manage monitoring and scientific collection of certain populations and foster increased collaboration among researchers (USFWS 2018, p.1). 6.A.6 BARRIERS TO FISH MOVEMENT T Central Texas mussels historically colonized new areas through movement of infested host fish, as newly metamorphosed juveniles would excyst from host fish in new locations. Today, the remaining Central Texas mussel populations are significantly isolated from one another by major reservoirs such that recolonization of areas previously extirpated is extremely unlikely if not impossible due to existing contemporary barriers to host fish movement. There is currently no opportunity for interaction among any of the extant Central Texas mussel populations as they are all fragmented from one another by reservoirs. AF The overall distribution of mussels is, in part, a function of the dispersal of their host fish. There is limited potential for immigration between populations other than through the attached glochidia being transported to a new area or to another population. Small populations are more affected by this limited immigration potential because they are susceptible to genetic drift (random loss of genetic diversity) and inbreeding depression. At the species level, populations that are eliminated due to stochastic events cannot be recolonized naturally, leading to reduced overall redundancy and representation. DR Many of the Central Texas mussels known or assumed primary host fish species are known to be common, widespread species in the Central Texas River basins. We have no reason expect the distribution of host fish to be a limiting factor in Central Texas Mussels distribution, other than the fact that populations of mussels and their host fish have become isolated over time following the construction of major dams and reservoirs throughout Central Texas. 6.A.7 CLIMATE CHANGE Climate change has been documented to have already taken place, and continued greenhouse gas emissions at or above current rates will cause further warming (Intergovernmental Panel on Climate Change (IPCC) 2013, pp. 11–12). Warming in the Southwest is expected to be greatest in the summer (IPCC 2013, pp. 11–12), and annual mean precipitation is very likely to decrease in the Southwest (IPCC 2013, pp. 11–12). In Texas, the number of extremely hot days (high temperatures exceeding 95º Fahrenheit) are expected to double by around 2050 (Kinniburgh et al. 2015, p. 83), and Texas is considered one of the “hotspots” of climate change in North America; West Texas is an area expected to show greater responsiveness to the effects of climate change (Diffenbaugh et al. 2008, p. 3). Even if precipitation and groundwater recharge remain at current levels, increased groundwater pumping and resultant aquifer shortages due to increased temperatures are nearly certain (Loaiciga et al. 2000, p. 193; Mace and Wade 2008, pp. 662, 664-665; Taylor et al. 2013, p. 3). Effects of climate change, such as air temperature increases and an increase in drought frequency and intensity, have been shown to be occurring throughout the range of Central Texas mussels (Kinniburgh et al. 2015, p. 88), and these effects are expected to exacerbate several of the stressors discussed above, such as water temperature and flow loss (Wuebbles et al. 2013, p. 16). Draft Central Texas Mussels SSA Report 96 April 2018 In the analysis of the future condition of the Central Texas mussels, which follows as Chapter 7, climate change is considered to be an exacerbating factor, contributing to the increase of fine sediments, changes in water quality, loss of flowing water, and predation. 6.A.8 MANAGEMENT ACTIONS Since the 2011 12-month finding on three of the Central Texas Mussels (USFWS 2011, entire) many agencies, NGOs and other interested parties have been working to develop voluntary agreements3 with private landowners to restore or enhance habitats for fish and wildlife in the region, including the Central Texas mussels. These agreements provide voluntary conservation including habitat enhancements that will, if executed properly, reduce threats to the species while improving in-stream physical habitat and water quality, as well as adjacent riparian and upland habitats. T Some publicly and privately owned lands in the watersheds occupied by Central Texas mussels are protected with conservation easements or are otherwise managed to support populations of native fish, wildlife, and plant populations. AF Work is underway to evaluate methods of captive propagation for the Central Texas mussel species at the Service’s hatchery and research facilities (San Marcos Aquatic Research Center, Inks Dam National Fish Hatchery, and Uvalde National Fish Hatchery) including efforts to collect gravid females from the wild to infest host fish (Bonner et al. 2018, pp. 8, 9, 11). 6.A.9 SUMMARY DR Our analysis of the past, current, and future influences on what the Central Texas mussels need for long term viability revealed that there are three influences that pose the largest risk to the future viability of the species. These risks are primarily related to habitat changes: the accretion of fine sediments, the loss of flowing water, and impairment of water quality; these are all exacerbated by climate change. The accretion of fine sediments, the loss of flowing water, changes in hydrology including floods leading to scour and subsequent substrate insuitability, inundation under reservoirs, the impairment of water quality, predation, collection, disease, and invasive species are carried forward in our assessment of the future conditions of Central Texas mussel populations and the viability of each species overall.                                                                   3 FWS Partners for Fish and Wildlife Program Private Lands Agreements and sub-recipient Cooperative Agreements, TPWD Landowner Incentive Program Agreements, USDA-NRCS Conservation plans including proposed Working Lands for Wildlife Projects, and others.  Draft Central Texas Mussels SSA Report 97 April 2018 CHAPTER 7 ‐ VIABILITY AND FUTURE CONDITIONS This report has considered what the four species of Central Texas mussels need for viability and the current condition of those needs (Chapters 3 and 5), and reviewed the risk factors that are driving the historical, current, and future conditions of the species (Chapter 6 and Appendix B). The report now considers what the species’ future conditions are likely to be in the foreseeable future. We apply our forecasts to the concepts of resiliency, redundancy, and representation to describe future viability of the four species of Central Texas mussels. 7.A INTRODUCTION AF T Each of the four species of Central Texas mussels has declined significantly in terms of overall distribution and abundance, relative to historical conditions, and over the past 100 or more years. Most of the known populations currently exist in very low abundances, with limited evidence of recruitment, and occupy much less habitat. Furthermore, existing available habitats are reduced in terms of quality and quantity, relative to historical conditions over the past 100 or more years. DR Beginning around the turn of the twentieth century, and by 1970, over 100 major dams had been constructed and reservoirs created across Texas, including several reservoirs in the Brazos and Trinity basins, the chain of Highland Lakes on the Lower Colorado River, the Guadalupe Valley Hydroelectric Project and the Canyon Reservoir on the Guadalupe River (Dowell 1964, pp. 3-8). The inundation and subsequent altered hydrology and sediment dynamics associated with operation of these flood-control, hydropower, and municipal supply reservoirs have resulted in irreversible changes to the natural flow regime of these rivers and ultimately has re-shaped these aquatic ecosystems, as well as the fish and invertebrate communities that depend on them, including populations of the four species of Central Texas mussels. Water quality impacts were common in many of the major rivers before modern sanitation, and in 1925 the Texas Department of Health called the Trinity a “mythological river of death” (USGS 1998, p. 19). Fortunately today, water quality has improved with dramatically improved wastewater treatment technology, such that fish populations have rebounded but not completely recovered (Perkin and Bonner 2016, p. 97). However, water quality impairment continues to affect mussels and their habitats, especially as low flow conditions and excessive sedimentation interact to diminish instream habitats, and substratemobilizing and mussel-scouring flood events have become more extreme if not more frequent. Additionally, while host fish may still be adequately represented in contemporary fish assemblages, access to fish hosts can be reduced during critical reproductive times by barriers such the many low-water crossings and low-head dams that now exist on the landscape. Low flows lead to dewatering of habitats and desiccation of individuals, elevated water temperatures and other quality impairments, as well as increased exposure to predation. Diminished access to host fish leads to reduced reproductive success just as barriers to fish passage impede the movement of fish, and thus compromise the ability of mussels to disperse and colonize new habitats following a disturbance (Schwalb et al. 2013, p. 1). Lastly, freshwater mussels have long been utilized by humans, for food and for bait, for pearls and buttons and for artificial pearl nuclei and even today rare mussels are vulnerable to human collection (Bogan 1993, pp. 604-5). Draft Central Texas Mussels SSA Report 98 April 2018 AF T Populations of each of the four Central Texas mussels face risks from natural and anthropogenic sources in both large and small river segments. Future higher air temperatures, higher rates of evaporation and transpiration, and changing precipitation patterns are expected in Central Texas (Jiang and Yang 2012, pp. 234-9, 242). Future climate changes are expected lead to human responses such as increased groundwater pumping and surface water diversions, associated with increasing demands for and decreasing availability of freshwater resources in the state (reviewed in Banner et al. 2010, entire). These risks, alone or in combination, could result in the extirpation of additional mussel populations, further reducing the overall redundancy and representation of each of the four species of Central Texas mussels. Historically, each species, with a large range of interconnected populations (i.e., with meta-population dynamics), would have been resilient to stochastic events such as drought, excessive sedimentation, and scouring floods because even if some locations were extirpated by such events, they could be recolonized over time by dispersal from nearby survivors and facilitated by movements by “affiliate species” of host fish (Douda et al. 2012, p. 536). This connectivity across potential habitats would have made for highly resilient species overall, as evidenced by the long and successful evolutionary history of freshwater mussels as a taxonomic group, and in North America in particular. However, under current conditions, restoration of that connectivity on a regional scale is not feasible. As a consequence of these current conditions, the viability of the four species of Central Texas mussels now primarily depends on maintaining the remaining isolated populations and potentially restoring new populations where feasible. 7.B. FUTURE SCENARIOS AND CONSIDERATIONS   DR Because of significant uncertainty regarding if and when flow loss, water quality impairments, extreme flooding and scour/substrate mobilizing events, or impoundment construction may occur, we have forecasted future viability for each of the four species of Central Texas mussels in terms of resiliency, redundancy, and representation under four plausible future scenarios (Table 7.1). Each scenario is projected across up to three time steps, and considers the biological status of mussel populations and their habitats in ten, twenty-five, and fifty years. Ten years represents one to two generations of mussels, assuming an average reproductive life span of five to ten years. Twenty-five years similarly represents two to four mussel generations. Fifty years represents five or more generations of mussels and corresponds with the current planning horizon the State Water Plans (from 2020 to 2070), a period of time for which the human population of the State of Texas is expected to grow 88% from 27 million to 51 million (TWDB 2017, p. 3) with much of the growth of human population occurring in the watersheds these four species of mussels currently occupy (TWDB 2017, pp. 50-51). The future scenarios also consider the interactive effects of future climate change, described by Representative Concentration Pathways (RCPs) under the WGIII model (IPCC 2014, pp. 9, 57). Scenarios 1 and 2 assume RCP4.5, which is commonly accepted among the scientific community to be the most realistic “best case scenario” where atmospheric carbon dioxide concentrations are between 580 and 720 ppm CO2-C between 2050 and 2100, representing an approximate +2.5 degree Celsius (ºC) temperature change relative to 1861-80. Scenario 3 assumes RCP6.0 where atmospheric carbon dioxide concentrations are between 720 and 1000 ppm CO2-C between 2050 and 2100, representing an approximate +3.5 ºC temperature change relative to 1861-80. Scenario 4 assumes RCP8.5 where atmospheric carbon dioxide concentrations are above 1000 ppm CO2-C between 2050 and 2100, Draft Central Texas Mussels SSA Report 99 April 2018 representing an approximate +4.5 ºC temperature change relative to 1861-80. The “business as usual” scenario is expected to fall between RCP6.0 and RCP8.5 (IPCC 2014, p. 57). The IPCC forecasts projected global temperature change to 2100 (2014, p. 8). T This species status assessment and report makes the following assumptions informed by the most recent Synthesis Report of the Intergovernmental Panel on Climate Change (IPCC 2014, entire) and other scientific studies. The IPCC Synthesis Report considers RCP4.5 and RCP6.0 as intermediate scenarios and RCP8.5 as having “very high” greenhouse gas emissions (IPCC 2014, p. 8). Under RCP4.5, current conditions, including a continued trend towards increased warming, frequency and severity of extreme events, such as droughts and floods, are expected to continue. Overall average surface temperature change is expected to exceed 1.5 ºC by 2100 (IPCC 2014, p. 60). Under RCP6.0, future conditions include an increasing trend towards increased warming, increased frequency and severity of extreme events, such as droughts and floods, are expected to manifest under future climate projections. Overall average surface temperature change is expected to exceed 2.0 ºC by 2100 (IPCC 2014, p. 60). Under RCP8.5, future conditions include a much increasing trend towards increased frequency and severity of extreme events, such as droughts and floods, are expected to manifest under future climate projections. Overall average surface temperature change is expected to exceed 2.0 ºC by 2100 (IPCC 2014, p. 60). DR AF For all IPCC RCP scenarios, extreme precipitation events over most mid-latitude land masses (like North America) will very likely become more intense and frequent as global mean surface temperature increases (IPCC 2014, p. 60) and, as such, future temperature and precipitation patterns are likely to become more variable and extreme, with drought and flooding events occurring more frequently and with higher severity in the southwestern United States (Seager et al. 2007, pp. 1183-4) and Texas (Shafer et al. 2014, pp. 443-446) including Central and South Texas (Jiang and Yang 2012, pp. 238-242). The magnitude of these changes is expected to increase with increasing greenhouse gas emissions and atmospheric concentrations. Given the inertia of the climate system and regardless of future emissions, the risk of flooding is expected to increase over the next 25-50 years, and these increases in the severity of extreme floods are expected to affect human systems (reviewed in Willner et al. 2018, entire, and Hirabayashi et al. 2013, entire), as well as freshwater mussels, aquatic organisms, and freshwater ecosystems in general. Future human demand for water resources, due to human population growth and limitations of existing supply, is expected to interact with climate effects and exacerbate the effects of droughts on surface water resources in Texas, which could possibly compete with the “environmental flow” needs of freshwater mussels and other flow-dependent aquatic organisms (Wolaver et al. 2014, pp. 1-2). The upper portions of the basins, including tributaries, will be more sensitive to changes in precipitation patterns and withdrawals, relative to the lower portions of the basins, where flows are increasingly dominated by wastewater (or other) return flows and where significant senior water rights located at the “bottom” of the basin help to protect flows. However, while minimum flows may be maintained, other artifacts of the altered hydrology may have deleterious effects to mussels and their habitats through altered water quality, and changes in sediment transport (more extreme deposition and scour) leading to reductions in habitat quality and quantity. The City of Austin commissioned a report that projected future climate for Austin, Texas, using nine models from the Coupled Model Intercomparison Project phase 5 (CMIP5) under RCP4.5 and RCP8.5 scenarios (Hayhoe 2014, p. 3). This report found, using downscale projections for Camp Mabry, that Draft Central Texas Mussels SSA Report 100 April 2018 summer average high temperature would increase from 93.8 ºF to 97.9 ºf under RCP4.5 and to 100.2 ºF under RCP8.5, annual precipitation would be largely unchanged (33.7 inches per year to 33.6 inches per year and 33.3 inches per year under RCP4.5 and RCP8.5, respectively), but that the number of extreme precipitation events (wet days having > 2 inches in 24 hours) increased from 2.2 events per year to 2.8 under RCP4.5 and to 2.7 under RCP8.5 (Hayhoe 2014, p. 8). The report concluded that “climate in Texas is already changing…consistent with larger-scale trends” and projected changes include “increases in annual and seasonal average temperature...little change in annual average precipitation…more frequent extreme precipitation…and more frequent drought conditions in summer due to hotter weather” (Hayhoe 2014, p. 9). DR AF T This report describes and suggests four plausible scenarios (Table 7.2). The first scenario, Scenario 1, extrapolates the current direction and magnitude of current population trends and condition trajectories to the future, and represents a continuation of current conditions projected across the next 10, 25, and 50 years. That is, existing declines in habitat and population condition factors continue to decline, and past droughts and floods re-occur at approximately the same interval and magnitude for the next 50 years. Scenario 1 assumes that ongoing, or at least initiated, activities continue over the next 50 years, and includes actions that might either benefit or hinder the future resiliency of Central Texas mussel populations. The second scenario, Scenario 2, explores possible conservation strategies that if implemented, could maintain the status quo current conditions, thus slowing or halting declines in habitat and population conditions in 10-25 years and in some cases slightly reversing declines to improve habitat and population conditions in 25-50 years. Scenario 2 implements new conservation strategies that may or may not have been actually proposed, but known currently ongoing strategies are also included in Scenario 1. Both Scenario 1 and Scenario 2 assume RCP4.5 climate change predictions, representing fairly optimistic emissions conditions and resulting climate forcings. Like Scenario 1, both Scenario 3 and Scenario 4 also project current population trends and condition categories in the future, but instead apply RCP6.0 and RCP8.5 predictions. Further, Scenario 3 also includes anthropogenic actions, such as the construction of new reservoirs, wastewater treatment plants, and other currently proposed projects. Scenario 4 includes all actions expected to take place under Scenario 3 and adds the construction of projects that have not actually been proposed. Most notably, Scenario 3 and Scenario 4 manifest as futures where the hydrological conditions of many of the rivers and streams currently occupied by Central Texas mussels are altered such that base flows are diminished, floods are more severe if not more frequent such that mussels and their habitats are adversely affected through degradation of water and habitat quality and quantity. These altered hydrological conditions are primarily caused by a combination anthropogenic factors and climate forcings. Draft Central Texas Mussels SSA Report 101 April 2018 Table 7.1. Plausible Future Scenarios, by RCP* and time step. RCP* 10-years 25-years 50-years 1 - Continuation (of Current Conditions) 4.5 0-10 yrs 10-25 yrs 25-50 yrs 2 - (Additional) Conservation 4.5 0-25 yrs 25-50 yrs 3 - RCP6.0 6.0 0-25 yrs 25-50 yrs 4 - RCP8.5 8.5 0-25 yrs 25-50 yrs T Future Scenario AF *RCP = Representative Concentration Pathway Scenario (IPCC 2014, pp. 9, 57) DR We examined the resiliency, representation, and redundancy of the four mussel species under each of these four plausible scenarios for each the three time periods (Table 7.2). We only projected Scenario 1 at the 10-year time step, as we do not expect there to be many differences between any of the scenarios in 10 years; in other words, no matter which trajectory the species are following, the populations are likely to look the same in 10 years at the scale of our analysis. Resiliency of populations of these species depends on future water quality, availability of flowing water, and substrate suitability and how these habitat factors influence species reproduction, abundance, and the amount of habitat occupied. We expect the extant populations of these mussel species to experience changes to these aspects of their habitat in different ways under the different scenarios. We projected the expected future resiliency of each population based on the events that would occur under each scenario. We then projected the overall condition for each population based on these habitat and population factors. For these projections, populations in healthy condition are expected to have high resiliency at that time period; i.e., they occupy habitat of sufficient size to allow for ebbs and flows of density of mussel beds within the population. Populations in healthy condition are expected to persist into the future (> 90% chance of persistence beyond 20 years), and have the ability to withstand stochastic events that may occur. Populations in moderately healthy condition have lower resiliency than those in healthy condition, but the majority (6090 %) are expected to persist beyond 20 years. Populations in moderately healthy condition are smaller and less dense than those in healthy condition. Populations in unhealthy condition have low resiliency and are not necessarily able to withstand stochastic events. As a result, they are less likely to persist beyond 20 years (10-60 % chance). Finally, populations are considered extirpated, either completely (lack of individuals) or functionally (lack of reproduction), and have very low resiliency and have less than a 10 % chance of persistence beyond 20 years. Draft Central Texas Mussels SSA Report 102 April 2018 7.B.1 SCENARIO 1 Scenario 1, Continuation of Current Conditions, considers a future where the current levels of existing degradation as well as existing conservation, current as of the preparation of this SSA report, continue for the next 50 years (Table 7.2), and those effects on mussels and their habitats are considered over the next 0-10, 10-25, and 25-50 years. Existing planned and initiated conservation efforts will continue, but are not significantly expanded. Planned but not initiated efforts are considered in Scenario 2 rather than Scenario 1. Existing patterns of development, including urbanization, irrigation, and other water uses continue increasing trends. Construction of new reservoirs currently under development are completed and inundated, with effects to mussels evident in the next 0-10 years. T 7.B.2 SCENARIO 2 AF Scenario 2, Additional Conservation, considers a future where “feasible and appropriate conservation plans” are implemented over the next 0-25 and 25-50 years (Table 7.2). Scenario considers which conservation actions could be implemented in the next 0-25 years, and what improvements to mussels and their habitats could be accomplished in the next 0-25 and 25-50 years. These positive conservation actions, if implemented, are expected to maintain, or improve somewhat, habitat and population conditions at the status quo over the next 25 to 50 years. DR Scenario 2 assumes that some actions of positive intervention are thoughtfully designed and executed as “feasible and appropriate conservation plans.” Such plans may be implemented by a combination of federal, state, and local governments, including river authorities, municipalities, and other “water regulators” along with NGO conservation groups, private landowners, and other stakeholders informed by government, academic, and consulting biologists with expertise in the conservation of freshwater mussels and their habitats. Some elements of such conservation plans include the following: ● ● Establishment of a research center and comprehensive program to conduct basic and applied research into the biology, ecology, management, conservation, and restoration of populations of rare mussels, including the Central Texas Mussels. One example of such a research center that is well known is the Alabama Aquatic Biodiversity Center. This report acknowledges several efforts that currently underway including: Texas A&M AgriLife Research and Extension Center at Dallas, partnerships between Texas State University and the USFWS San Marcos Aquatics Resources Center and Inks Dam and Uvalde National Fish Hatcheries (partially funded by the State of Texas Office of the Comptroller’s Endangered Species Program), efforts by Texas Parks and Wildlife Department, and individual and collaborative efforts by River Authorities in Texas. While none of these efforts yet represent an “established research center and comprehensive program,” this report considers it practicable that one or more of these efforts could rise to that level in the next 0-25 years. This effort would include development and implementation of genetics management plans to inform the current, past, and desired future genetic structure by population for each species. Establishment of a framework, like an interagency working group, to achieve coordination and collaboration among researchers and other collectors of Central Texas mussels. Such a framework would help facilitate collaborative research and conservation efforts. This report Draft Central Texas Mussels SSA Report 103 April 2018 ● ● DR ● T ● AF ● acknowledges several efforts currently underway including: Texas Freshwater Mussel Conservation Society, which hosts biennial research symposia and identification workshops, the Comptroller’s Office Freshwater Mussel Working Group, and other informal collaborations. While none of these efforts alone, or in combination, yet represent an “established framework”, this report considers it practicable that one or more of these efforts could rise to that level in the next 0-25 years. Complementary to this effort to foster collaboration, is an effort to control “loosely” regulated collection and scientific use. This effort could come out of an interagency working group, or could possibly be implemented by Texas Parks and Wildlife Department. Active efforts to protect, maintain, and improve existing water quality in waters affecting important mussel populations. Examples include improved watershed management, management of livestock access to riparian areas, upgraded wastewater treatment facilities, etc. Active efforts to protect, maintain, and improve existing water quantity in waters known to be important for mussel populations. This report acknowledges several efforts currently underway including: The Texas Instream Flow Program (also known as Senate Bill 2), the Environmental Flows Process (also known as Senate Bill 3). Active efforts to protect, maintain, and improve existing habitats for important mussel populations. Implementation of private lands voluntary habitat enhancement and restoration programs at various scales, from the watershed to the local riparian and instream environment. This report acknowledges several efforts currently underway including: The Texas Landowner Incentive Program (LIP), a collaborative effort of TPWD Wildlife and Inland Fisheries Divisions, and other partners, to enhance habitats for terrestrial and aquatic species. A NRCS Working Lands for Wildlife (WLFW) Project has been proposed and is expected to begin implementation in 2018, in the Lower Colorado River Basin to encourage producers to implement water quality and other conservation practices to benefit freshwater mussels, among other species. Scenario 2 considers that established programs, like LIP, will continue and expand, and that proposed projects, like WLFW, will be successfully implemented in the next 0-25 years, and will have meaningful effects in the next 25-50 years. Management of exotic species and diseases. Scenario 2 considers that positive efforts will be made to mitigate against future threats of emerging exotic species and diseases. Examples include zebra mussels and trematodes. Reintroduction and repatriation of mussels in currently extirpated populations only and following restoration of suitable habitats. Compared with the other three Central Texas mussels, Texas fatmucket currently shows the greatest potential for successful captive propagation. This scenario includes the reintroduction of Texas fatmucket in Onion Creek in the next 0-25 years, with the population becoming moderately healthy in the next 25-50 years. Such reintroductions and repatriations are not possible today, but are expected to be possible in the next 0-25 years, and would require collaborations between the Service and others including, perhaps, the City of Austin. ● ● Draft Central Texas Mussels SSA Report 104 April 2018 7.B.3 SCENARIO 3 T Scenario 3, RCP6.0, considers a future where conditions are no better for the species than the status quo Current Conditions. RCP6.0 considers intermediate climate effects, including more frequent and intense droughts, where droughts are broken by major flooding (Table 7.2). RCP6.0 also considers Total annual runoff to the Colorado River is projected to  additional ground- and surface-water demands decrease under all climate change scenarios by 2050. The  decreases in the Colorado River streamflow near Lake Travis is  associated with increased human demand and projected to range from 17 percent to 38 percent with greater  decreased availability given intermediate climate changes in the upper basin and smaller changes in the lower  effects. Reductions in streamflow, due to basin (downstream of Austin). An important finding is that  decreased inputs and enhanced annual streamflow is projected to decrease even under  scenarios that exhibit small increases in precipitation. At these  evapotranspiration, are expected to occur in all moderate precipitation increases, evapotranspiration is the  streams and rivers, and those effects will be dominant hydrologic process affecting runoff changes. In the  more pronounced in the upper basins (see inset). lower basin, incremental runoff changes in the Colorado River  from Lake Travis to Bay City range from a reduction of 5  percent to an increase of 13 percent largely depending on the  precipitation projections in this region. Net evaporation is  projected to increase for all scenarios in the upper and middle  basin, ranging from 1.7 to 6.6 inches annually. Most scenarios  also exhibit increases in the lower basin, but one scenario with  increasing precipitation shows decreases in this region.  AF Scenario 3 considers additional water projects, like wastewater treatment plant outfalls, only if currently proposed or planned. Proposed new reservoirs from the 2017 State Water Plan (TWDB, 2016) are constructed in the next 10-25 years, and any effects from completion of these dams are manifest in the next 25-50 years. Necessary routine maintenance as well as repair and replacement of existing old dams (i.e., the Guadalupe Valley Hydroelectric Reservoirs) occurs in the next 10-25 years, and any effects from those repairs are manifest in the next 25-50 years. DR By 2080, three of the four climate change scenarios show  continued reductions in streamflow and increasing net  evaporation. Streamflows reductions range from 11 percent to  48 percent in the Colorado River near Lake Travis for these  three scenarios.  One scenario (CCSM B1), exhibiting a large  change in precipitation patterns in the upper basin, projects  increases in runoff of approximately 25 percent.  ‐‐ C2HM HILL (2008, p. ES‐2) Climate Change Study    7.B.4 SCENARIO 4 Scenario 4, RCP8.5, like RCP 6.0, considers a future where conditions are not better for the species than the status quo Current Conditions. RCP8.5 considers severe climate effects, including more frequent and intense droughts, where droughts are broken by major flooding (Table 7.2). RCP8.5 considers additional ground- and surface-water demands associated with increased human demand and decreased availability given severe climate effects. Scenario 4 considers additional water projects, like wastewater treatment plant outfalls, even if not currently proposed, as well as possible new reservoirs and other construction projects. Draft Central Texas Mussels SSA Report 105 April 2018 Table 7.2. Generalizations for projected trends in Habitat Factors by basin and occupied segment in Scenario 1, over time, and with notes from Scenario 2, Scenario 3, and Scenario 4: 10-25 years 25-50 years Flows will continue at existing low levels, with at least one critical dewatering event likely in the next 10 years, due to a combination of drought and withdrawals. Water quality impairment, due to elevated chlorides and bacteria, will continue, especially during low flow events (for chlorides) and following runoff events (for bacteria). Habitat quality will continue in its current status of degradation due to excessive sedimentation, scouring events that move unstable substrates, and low flow events that expose shallow habitats to desiccation. The City of Abilene Cedar Ridge Reservoir will be built in the next 10 years, inundating 29miles of the Clear Fork of the Brazos and 43miles of tributary streams, also resulting in “downstream impacts associated with hydrologic alterations” (FR 2018, p. 16062). Flows will continue such that water quality exists at “adequate” levels, and altered hydrology (associated with Flows will continue to decline to very low levels, with multiple critical dewatering events likely in the next 25 years, due to a combination of drought and withdrawals. Water quality impairment, due to chlorides and bacteria, will continue, especially during low flow events. Trend of declining flows and critical dewatering continues over the next 25-50 years, due to a combination of drought and withdrawals. Trend of declining water quality continues, especially given the effects with of diminishing flows on water quality and habitat availability. Habitat quality declines with increased sedimentation, exposure and desiccation associated with low flow events, and scouring associated with occasional floods. T 0-10 years Voluntary conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. But opportunities are limited given the drought exposure. AF Basin Brazos (Upper) Lower Clear Fork of the Brazos DR Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. Construction of the proposed Cedar Ridge Reservoir is completed, affecting mussels and their habitats downstream, due to changes in flows and habitat quality following construction and operation of the new reservoir. Brazos (Lower) Little River Middle/ Lower Draft Central Texas Mussels SSA Report Some improvements to the habitat factors are gained following establishment of voluntary conservation programs implemented to improve riparian and adjacent upland habitats. Same as 10-25 years. Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5 and significant hydrological alterations are manifest. Same as 10-25 years. In the Little River, flows will become more and more influenced by return flows and urban development (higher base flows, more flash flooding and scour). In the Little River, flows will become more and more influenced by return flows and urban development (higher base flows, more flash 106 April 2018 10-25 years 25-50 years reservoir management and return flows) will continue for the next 10 years. Flooding continues to become more severe because of continued development and land use practices that contribute to runoff in the watershed. Water quality impairment, due to bacteria and suspended solids (sedimentation) continues. Habitat quality impairments, due to development and land use practices in the watershed, will continue. Water quantity will continue at “adequate” levels, but the hydrographs will continue to shift towards more of a “return flows hydrology” with infrastructure development on the Little River and its tributaries. In the Middle/Lower Brazos, flows will continue such that water quality exists at “adequate” levels, and altered hydrology (associated with reservoir management, return flows, and environmental flow considerations) will continue for the next 25 years. More flooding due to continued development and land use in the watershed. Water quality impairments will continue, due to development and land use in the watershed. Habitat quality will be diminished by flow alterations (floods), sedimentation, and mobilization of substrate. flooding and scour). Water quantity will continue at “adequate” levels, but the hydrographs will continue to shift towards more of a “return flows hydrology” with infrastructure development on the Little River and its tributaries. In the Middle/Lower Brazos, flows will continue such that water quality exists at “adequate” levels, and altered hydrology (associated with reservoir management and return flows) will continue for the next 25-50 years. More flooding due to continued development and land use in the watershed. Water quality impairments will continue, due to development and land use in the watershed. Habitat quality will be diminished by flow alterations (floods), sedimentation, and mobilization of substrate. Some improvements to the habitat factors are gained following establishment of conservation programs. T 0-10 years AF Basin Brazos River DR Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. These effects are mitigated somewhat by return flows. The proposed Little River Off-Channel Reservoir is completed, and affects mussels and their habitats in the vicinity of and downstream of the impoundment and diversion structures. The proposed Allens Creek Reservoir is constructed, with detrimental effects to downstream mussels and their habitats. Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate change. Same as 10-25 years. Droughts are much exacerbated by Draft Central Texas Mussels SSA Report 107 April 2018 Flows will continue to be variable, and low at times, due to seasonal patterns of rainfall (i.e., drought), surface-water diversion and groundwater extraction. During these dry periods, water quantity, quality, and habitat only marginally meet the needs of the species. Some segments may begin to receive return flows, which bring more reliable water quantity, altered flows (more flooding), and uncertain effects to water quality. 10-25 years 25-50 years changing weather patterns and increased human demands under RCP8.5. These effects are mitigated somewhat by return flows, depending on the amount of reuse. Low and variable flows, exacerbated by climate change and concomitant increased demand, will continue such that water quantity, quality, and habitat are no longer suitable for meeting the needs of the species in many reaches of occupied segments. Water quality will be diminished by low flows and land use practices in the watershed, along with development where it may be occurring. Habitat quality will be diminished by low flows, sedimentation, and by flash flooding events (exacerbated by climate change, land use, and development).  Trend of declining flows and critical dewatering continues over the next 25-50 years, due to a combination of drought and withdrawals. Trend of declining water quality continues, especially given the effects with of diminishing flows on water quality and habitat availability. Habitat quality declines with increased sedimentation, exposure and desiccation associated with low flow events, and scouring associated with occasional floods. T Colorado (Upper) Lower Elm Creek Lower Concho River Upper/ Middle San Saba River Lower San Saba River Llano River Pedernales River 0-10 years AF Basin DR Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. Implemented conservation strategies successfully mitigate risks of further declines, and in some cases reverse declines, in habitat factors and result in modest improvement in population factors. Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate change. A combination of climate forcings and anthropogenic responses to water shortages results in significant and Draft Central Texas Mussels SSA Report 108 April 2018 Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management) will continue for the next 10 years. Lower Onion Creek will become more of a “return flows system” with the completion of the Dripping Springs water plant. Water quality of Onion Creek will diminish with increasing development and land use changes in the watershed. Habitat quality will continue to be diminished by low flows, sedimentation, and by flooding. Some conservation (water quality protection initiatives, land acquisition, conservation easements, etc.) is being planned and implemented in Onion Creek. 10-25 years 25-50 years Flows will become more and more influenced by return flows and development (higher base flows, more flash flooding and scour). Flows will continue at “adequate” levels, but the hydrographs will continue to shift towards more of a “return flows hydrology” with infrastructure development in the Austin metro area. Irrigation use downstream will continue to affect water quantity, increasing risk of exposure, quality effects, and habitat degradation, especially during drought years. Water quality impairments likely to continue. Habitat quality diminishments likely to continue. severe alteration of hydrological conditions, such that both dewatering events and scouring floods are more frequent and severe. Flows will become more and more influenced by return flows and development (higher base flows, more flash flooding and scour). Flows will continue at “adequate” levels, but the hydrographs will continue to shift towards more of a “return flows hydrology” with infrastructure development in the Austin metro area. Irrigation use downstream will continue to affect water quantity, increasing risk of exposure, quality effects, and habitat degradation, especially during drought years. Water quality impairments likely to continue. Habitat quality diminishments likely to continue. AF Colorado (Lower) Lower Onion Creek Lower Colorado River 0-10 years T Basin DR Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Texas fatmucket restored in Onion Creek. Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. These effects are mitigated somewhat by return flows. Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. These effects are mitigated somewhat by return flows, depending on the amount of reuse. Implemented conservation strategies successfully mitigate risks of further declines, and in some cases reverse declines, in habitat factors and result in modest improvement in population factors. Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate change. A combination of climate Draft Central Texas Mussels SSA Report 109 April 2018 Guadalupe (Upper) Upper Guadalupe River 0-10 years Flows will continue to be variable, and sometimes low, due to seasonal patterns of rainfall and surface-water diversion and ground-water extraction. 10-25 years 25-50 years Because of spring flow, flows will continue to be variable, and sometimes low, due to seasonal patterns of rainfall and surfacewater diversion and ground-water extraction. Flash floods will increase in severity, resulting in more scour and loss of habitat. forcings and anthropogenic responses to water shortages results in significant and severe alteration of hydrological conditions, such that both dewatering events and scouring floods are more frequent and severe. Because of spring flow, flows will continue to be variable, and sometimes low, due to seasonal patterns of rainfall and surface-water diversion and ground-water extraction. Flash floods will increase in severity, resulting in more scour and loss of habitat. T Basin Implemented conservation strategies successfully mitigate risks of further declines, and in some cases reverse declines, in habitat factors and result in modest improvement in population factors. AF Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. DR Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. Draft Central Texas Mussels SSA Report Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate change. A combination of climate forcings and anthropogenic responses to water shortages results in significant and severe alteration of hydrological conditions, such that both dewatering events and scouring floods are more frequent and severe. 110 April 2018 0-10 years 10-25 years 25-50 years Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management) will continue for the next 10 years. Protected spring flows from the San Marcos (EAHCP) and Guadalupe Rivers (GBRA-TAP agreement) will, and with increasing return flow contributions from municipal return flows, will sustain “adequate” water quantity in the Lower parts of this basin, during dry times. Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management) will continue for the next 25 years. Protected spring flows from the San Marcos and Guadalupe Rivers will, as increasing return flow contributions from municipal return flows will sustain “adequate” water quantity. Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management) will continue. Benefits from flow protections will continue. Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate change. T Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Implementation of conservation strategies successfully maintains status quo current habitat factors. Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. These effects are mitigated somewhat by return flows, depending on the amount of reuse. AF Basin Guadalupe (Lower) Lower Guadalupe River Lower San Marcos River DR Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. These effects are mitigated somewhat by return flows, depending on the amount of reuse. In this highly managed system, likely no significant changes, but rather a continuation of current trends. Trinity Lower East Fork of the Trinity River In this highly managed system: Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management) will continue for the next 10 years. Return flows, and management of reuse flows, are expected to maintain “adequate” flow. Some flow Draft Central Texas Mussels SSA Report Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Droughts are exacerbated by changing weather patterns and increased human demands under RCP6.0. These effects are mitigated somewhat by return 111 A combination of climate forcings and anthropogenic responses to water shortages results in significant and severe alteration of hydrological conditions, such that both dewatering events and scouring floods are more frequent and severe. In this highly managed system, likely no significant changes, but rather a continuation of current trends. Conservation strategies planned are implemented. Negative impacts to habitat factors cause declines in habitat conditions, due to anthropogenic impacts and climate forcing associated with continued increasing human demand and climate April 2018 10-25 years 25-50 years protections exist associated with permitting of the East Fork Water Reuse Project (NTMD). flows, depending on the amount of reuse. change. In this highly managed system: Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management and stormwater runoff from significant urban development) will continue for the next 10 years. Return flows, significant reuse, interbasin transfers, downstream senior rights, and agreements with the City of Houston guarantee that at least “30% of return flows originating in the Trinity basin will remain in the river to Lake Livingston (TRA letter 2018). Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. These effects are mitigated somewhat by return flows, depending on the amount of reuse. In this highly managed system, likely no significant changes, but rather a continuation of current trends. Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management and stormwater runoff from significant urban development) will continue for the next 25 years. Return flows, significant reuse, interbasin transfers, downstream senior rights, and agreements with the City of Houston guarantee that at least “30% of return flows originating in the Trinity basin will remain in the river to Lake Livingston (TRA letter 2018). Hydrological alterations (higher baseflows due return flows and exaggerated flooding due to increased impervious cover) expected to increase (greater departure from a “natural flow” regime) with increasing human development. Water quality continues to improve following improved treatment of reused water. A combination of climate forcings and anthropogenic responses to water shortages results in significant and severe alteration of hydrological conditions. In this highly managed system, likely no significant changes, but rather a continuation of current trends. Flows will continue at existing “adequate” levels, and existing altered hydrology (associated with reservoir management and stormwater runoff from significant urban development) will continue, and perhaps increase, over the next 50 years, due to additional reuse and interbasin transfers. Return flows, significant reuse, interbasin transfers, downstream senior rights, and agreements with the City of Houston guarantee that at least “30% of return flows originating in the Trinity basin will remain in the river to Lake Livingston (TRA letter 2018). Hydrological alterations (higher baseflows due return flows and exaggerated flooding due to increased impervious cover) expected to increase (greater departure from a “natural flow” regime) with increasing human development. Water quality continues to improve following improved treatment of reused water. DR AF Trinity Middle Trinity River 0-10 years T Basin Conservation strategies are planned and implemented to protect flows, water quality, and riparian habitats and adjacent uplands. Droughts are exacerbated by Draft Central Texas Mussels SSA Report 112 April 2018 Basin 0-10 years 10-25 years 25-50 years changing weather patterns and increased human demands under RCP6.0. These effects are mitigated somewhat by return flows, depending on the amount of reuse. Same as 10-25. Same as 10-25. ● Return flows (wastewater effluent, interbasin exchange, groundwater “converted” to surface water) will continue to contribute to base flows in the lower portions of the basins below major metropolitan areas (DFW, Austin, and to a lesser extent, Waco and San Marcos). However, reuse may increase in the future, which could result in reductions to return flows. ● Drought (seasonal rainfall patterns combined with associated increased withdrawals/diversions) is expected to increasingly have adverse effects on flows in the upper portions of the basins, and tributaries. Drought effects in the lower basins are mitigated for the most part by return flows (see above). ● In the future, floods are expected to be more severe if not more frequent. Climate change and land use changes are expected to exacerbate flooding in the future AF Assumptions T Droughts are much exacerbated by changing weather patterns and increased human demands under RCP8.5. These effects are mitigated somewhat by return flows, depending on the amount of reuse. 7.C VIABILITY (RESILIENCY, REDUNDANCY, AND REPRESENTATION) DR   This section generally reviews the viability of the four Central Texas mussel species under each of the four scenarios. The output of the scenarios at each time step for each species are included in Appendix C, and synopses of the effects to the populations over time are included in Appendix D. 7.C.1. SCENARIO 1 R ESILIENCY Under Scenario 1, populations of all four Central Texas mussel species decline in resiliency over time as those factors that are having an influence on populations of Central Texas mussels continue at current rates (Table 7.3). The effects of current levels of climate change continue to result in low streamflows, which lead to increased sedimentation, reduced water quality, and occasional desiccation. Population extirpations occur to all four species, with no species having any populations in better than moderate condition. Those populations in unhealthy condition are particularly vulnerable to extirpation. Draft Central Texas Mussels SSA Report 113 April 2018 R EDUNDANCY All four Central Texas mussels lose redundancy under Scenario 1 (Table 7.3). Under our projections, only the Texas fawnsfoot and Texas fatmucket would have more than one population in a representation area in 50 years. DR AF T R EPRESENTATION Under Scenario 1, three of the four species of Central Texas mussels lose an area of representation (Table 7.3). Texas fawnsfoot may maintain representation in each watershed, but remaining populations are in unhealthy condition and are vulnerable to extirpation. The remaining species have lost areas of representation and, therefore, adaptive capacity to future environmental change. Draft Central Texas Mussels SSA Report 114 April 2018 Scenario 1 Table 7.3 Conditiona of four Central Texas freshwater mussel species populations under Scenario 1 in the Guadalupe, Colorado, Brazos, and Trinity River watersheds. Watershed (West to East) Population (North to South) Guadalupe River Upper Guadalupe False Spike 10 25 50 Lower Guadalupe San Marcos / Lower Guadalupe M M Texas Pimpleback 10 25 50 U U X M M M Concho X U U Pedernales X U X X X X X X M U U X X X X M U U X X X M U X U U X Onion Creek Lower Colorado M U X Brazos River Clear Fork Brazos Upper Brazos Little River Lower Brazos U U DR a X X M M U X U X X X X M M M U U U U U U U Trinity River East Fork Trinity Lower Trinity # of Populations Healthy Moderately healthy Unhealthy Extirpated / Functionally extirpated # of Representation Units (Watersheds) X U X X AF Llano U T Upper/Middle San Saba X U Texas Fawnsfoot 10 25 50 M Colorado River Bluff and Elm Creek Lower San Saba Upper Colorado and Lower San Saba Texas Fatmucket 10 25 50 0 1 2 4 0 1 1 0 1 1 0 3 3 7 0 1 3 0 1 0 0 2 3 6 0 0 4 0 0 2 0 2 3 7 0 2 2 0 1 3 1 2 2 1 3 6 1 2 4 2 3 3 3 2 2 2 2 1 2 2 1 3 3 3 Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). 7.C.2. SCENARIO 2 R ESILIENCY Under Scenario 2, populations of all four Central Texas mussel species generally maintain, or slightly improve, resiliency over time as conservation measures are implemented to counteract existing stressors (Table 7.4). The effects of current levels of climate change continue to result in low stream flows, which lead to increased sedimentation, reduced water quality, and occasional desiccation, but water conservation Draft Central Texas Mussels SSA Report 115 April 2018 measures and riparian improvements aid some populations. Even so, three of the four species experience at least one population extirpation, and only false spike and Texas fawnsfoot have single populations in healthy condition; all other populations are in moderate or worse condition. Those populations in unhealthy condition are particularly vulnerable to extirpation. R EDUNDANCY All four Central Texas mussels generally maintain redundancy under Scenario 2 (Table 7.4). Under our projections, several populations are extirpated but not to the same degree as in other scenarios. DR AF T R EPRESENTATION Under Scenario 2, all four Central Texas mussels generally maintain representation over time (Table 7.4). False spike has a single, unhealthy population in two of the three representation areas even under the conservation scenario, but we do not project complete loss of any representation area by any species under this scenario. Draft Central Texas Mussels SSA Report 116 April 2018 Table 7.4. Conditiona of four Central Texas freshwater mussel species populations under Scenario 2 in the Guadalupe, Colorado, Brazos, and Trinity River watersheds. Watershed (West to East) Population (North to South) Guadalupe River Upper Guadalupe Lower Guadalupe San Marcos/Lower Guadalupe False Spike 25 50 M Texas Pimpleback 25 50 U U M M Concho X U Llano Pedernales U U X M U U U U X X U U U M M U U M M Brazos River Clear Fork Brazos Upper Brazos Little River Lower Brazos U DR a U M H U U U X M M M M M M U Trinity River East Fork Trinity Lower Trinity # of Populations Healthy Moderately healthy Unhealthy Extirpated / Functionally extirpated # of Representation Units (Watersheds) X M U M AF Onion Creek Lower Colorado M T Upper/Middle San Saba Upper Colorado and Lower San Saba U Texas Fawnsfoot 25 50 H Colorado River Bluff and Elm Creek Lower San Saba Texas Fatmucket 25 50 4 7 6 7 0 1 2 1 1 0 2 1 0 2 4 1 0 4 2 1 0 1 5 0 0 3 3 0 0 4 2 1 1 3 2 1 3 3 2 2 2 2 3 3 Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). Draft Central Texas Mussels SSA Report 117 April 2018 7.C.3. SCENARIO 3 R ESILIENCY Under Scenario 3, populations of all four Central Texas mussel species decline in resiliency over time as climate change begins to affect populations (Table 7.5). The effects of intermediate levels of climate change result in lower stream flows, which lead to increased sedimentation, reduced water quality, and desiccation. Population extirpations occur to all four species, and no species with populations in any condition better than unhealthy; those population in unhealthy condition are particularly vulnerable to extirpation. Furthermore, false spike, Texas fatmucket, and Texas pimpleback only have one population in unhealthy condition, leaving those three species the most vulnerable to extinction. T R EDUNDANCY All four Central Texas mussels lose redundancy under Scenario 3 (Table 7.5). Under our projections, only the Texas fawnsfoot would have more than one population in 50 years. All populations remaining of all species would be in unhealthy condition and vulnerable to extirpation. DR AF R EPRESENTATION Under Scenario 3, three of the four species of Central Texas mussels lose an area of representation (Table 7.5). Texas fawnsfoot may maintain representation in each watershed, but remaining populations are in unhealthy condition and are vulnerable to extirpation. The remaining species have lost areas of representation and, therefore, adaptive capacity to future environmental change. Draft Central Texas Mussels SSA Report 118 April 2018 Table 7.5. Conditiona of four Central Texas freshwater mussel species populations under Scenario 3 in the Guadalupe, Colorado, Brazos, and Trinity River watersheds. Watershed (West to East) Population (North to South) Guadalupe River Upper Guadalupe Lower Guadalupe San Marcos/Lower Guadalupe False Spike 25 50 M Texas Pimpleback 25 50 U X M U X X X X Concho Upper/Middle San Saba Llano X X U X X U X X X U U X AF Onion Creek Lower Colorado X X X Pedernales X U X Upper Brazos U DR a M U X X X X M U U U U U X Trinity River East Fork Trinity Lower Trinity # of Populations Healthy Moderately healthy Unhealthy Extirpated / Functionally extirpated # of Representation Units (Watersheds) X U X X Brazos River Clear Fork Brazos Little River Lower Brazos X T Upper Colorado and Lower San Saba U Texas Fawnsfoot 25 50 U Colorado River Bluff and Elm Creek Lower San Saba Texas Fatmucket 25 50 4 7 6 7 0 1 1 2 0 0 1 3 0 1 3 3 0 0 1 6 0 0 4 2 0 0 1 5 0 2 2 3 0 0 4 3 2 1 2 1 2 1 3 3 Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). Draft Central Texas Mussels SSA Report 119 April 2018 7.C.4. SCENARIO 4 R ESILIENCY Under Scenario 4, populations of all four Central Texas mussel species decline in resiliency over time as severe climate change begins to affect populations (Table 7.6). The effects of strong levels of climate change result in even lower stream flows, which lead to increased sedimentation, reduced water quality, and desiccation. Population extirpations occur to all four species, and no species with populations in any condition better than unhealthy; those population in unhealthy condition are particularly vulnerable to extirpation. Furthermore, false spike, Texas fatmucket, and Texas pimpleback only have one population in unhealthy condition, leaving those three species the most vulnerable to extinction. T R EDUNDANCY All four Central Texas mussels lose redundancy under Scenario 4 (Table 7.6). Under our projections, only the Texas fawnsfoot would have more than one population in 50 years. All populations remaining of all species would be in unhealthy condition and vulnerable to extirpation. DR   AF R EPRESENTATION Under Scenario 4, all four species of Central Texas mussels lose an area of representation (Table 7.6). All remaining populations of all species are in unhealthy condition and are vulnerable to extirpation. The remaining species have lost areas of representation and, therefore, adaptive capacity to future environmental change. All species are extremely vulnerable to extinction under Scenario 4. Draft Central Texas Mussels SSA Report 120 April 2018 Table 7.6. Conditiona of four Central Texas freshwater mussel species populations under Scenario 4 in the Guadalupe, Colorado, Brazos, and Trinity River watersheds. Watershed (West to East) Population (North to South) Guadalupe River Upper Guadalupe Lower Guadalupe San Marcos/Lower Guadalupe False Spike 25 50 M Texas Pimpleback 25 50 X X M U Concho X X Llano Pedernales X X X X U X X X X X X X X X U X X AF Onion Creek Lower Colorado X T Upper/Middle San Saba Upper Colorado and Lower San Saba X X X Upper Brazos X DR a X U X X X X X M Trinity River East Fork Trinity Lower Trinity # of Populations Healthy Moderately healthy Unhealthy Extirpated / Functionally extirpated # of Representation Units (Watersheds) X U X X Brazos River Clear Fork Brazos Little River Lower Brazos Texas Fawnsfoot 25 50 U Colorado River Bluff and Elm Creek Lower San Saba Texas Fatmucket 25 50 4 7 U U 6 U U 7 0 1 0 3 0 0 1 3 0 1 0 6 0 0 1 6 0 0 2 4 0 0 1 5 0 1 3 3 0 0 2 3 1 1 1 1 1 1 3 1 Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). Draft Central Texas Mussels SSA Report 121 April 2018 7.D STATUS ASSESSMENT SUMMARY   Using the best available information, this report used scenario planning to forecast the likely future condition of the false spike, Texas fatmucket, Texas fawnsfoot, and Texas pimpleback, across the range of habitats they occupy in Central Texas. The goal of this report is to describe the viability of each species in terms of resiliency, representation, and redundancy. This report considers the possible future condition of each species, and a range of potential scenarios that include important influences on the current and future status of the false spike, Texas fatmucket, Texas fawnsfoot, and Texas pimpleback. The results of this analysis describe a range of possible future conditions, whereby populations of false spike, Texas fatmucket, Texas fawnsfoot, and Texas pimpleback are likely to persist into the future. AF T Each of these species face a variety of risks from a range of hydrological alterations to their habitats, including loss of flow leading to dewatering, excessive flows leading to scouring, water quality impairments, degradation of suitable substrates due to excessive sedimentation and other processes, inundation, and population isolation. Other factors contribute, or exacerbate exposure, to these risks but are not directly driving population condition. These secondary factors include: depredation, disease, invasive species, over-collection and/or vandalism, exposure to environmental contaminants, and host fish interactions, among others. These risks together substantially affect the future viability of the false spike, Texas fatmucket, Texas fawnsfoot, and Texas pimpleback. If population resiliency (the ability to withstand stochastic events and described by demographic factors including population size and growth rate) is diminished, populations are more vulnerable to extirpation. Population extirpations result in losses to redundancy (the ability of a species to withstand catastrophic events) and diminishment of species representation (important breadth of genetic and ecological diversity). DR False spike is currently represented by one moderately healthy population and three unhealthy populations. Within 50 years, even under the best conditions and with additional conservation, given the ongoing effects climate change and human activities on altered hydrology and habitat degradation, one population is expected to become functionally extirpated, two are expected to be in an overall unhealthy condition, and one population is expected to be in healthy condition (Table 7.4). Given the likelihood of increased climate and anthropogenic effects in the foreseeable future, three populations are expected to become functionally extirpated, leaving just one unhealthy population remaining in 50 years (Table 7.6). Texas fatmucket is currently represented by two moderately healthy populations, three unhealthy populations, and one functionally extirpated population. Within 50 years, even under the best conditions and with additional conservation, given the ongoing effects climate change and human activities on altered hydrology and habitat degradation, three populations are in moderately healthy condition (including the functionally extirpated population), and three are in unhealthy condition (Table 7.4). Given the likelihood of increased climate and anthropogenic effects in the foreseeable future, five populations are expected to become functionally extirpated, leaving just one unhealthy population remaining in 50 years (Table 7.6). Draft Central Texas Mussels SSA Report 122 April 2018 Texas fawnsfoot is currently represented by two moderately healthy populations and five unhealthy populations. Within 50 years, even under the best conditions and with additional conservation, given the ongoing effects climate change and human activities on altered hydrology and habitat degradation, one population is in healthy condition, one population is in moderately healthy condition, four populations are in unhealthy condition, and one population is functionally extirpated (Table 7.4). Given the likelihood of increased climate and anthropogenic effects in the foreseeable future, as many as five populations are expected to become functionally extirpated, leaving no more than three unhealthy populations remaining in 50 years (Table 7.6). DR AF T Texas pimpleback is currently represented by three moderately healthy populations and four unhealthy populations. Within 50 years, even under the best conditions and with additional conservation, given the ongoing effects climate change and human activities on altered hydrology and habitat degradation, four populations are in moderately healthy condition, two are in unhealthy condition, and one population is functionally extirpated (Table 7.4). Given the likelihood of increased climate and anthropogenic effects in the foreseeable future, six populations are expected to become functionally extirpated, leaving only one unhealthy population remaining in 50 years (Table 7.6).     Draft Central Texas Mussels SSA Report 123 April 2018 7.E SUPPLEMENTARY TABLES AND FIGURES SUMMARY OF FUTURE POPULATION CONDITIONS BY RIVER BASIN Guadalupe River, Table 7.7 Colorado River, Table 7.8 Brazos River, Table 7.9 Trinity River, Table 7.10   False spike, Table 7.11, Figure 7.1 Texas fatmucket, Table 7.12, Figure 7.2 AF Texas fawnsfoot, Table 7.13, Figure 7.3 T SUMMARY OF FUTURE POPULATION CONDITION BY SPECIES   DR Texas pimpleback, Table 7.14, Figure 7.4  Draft Central Texas Mussels SSA Report 124 April 2018 T Table 7.7. Number of populations of False spike, Texas pimpleback, and Texas fatmucket by population conditiona under future scenarios b in the Guadalupe River watershed. False Texas Texas Spike pimpleback fatmucket H M U X H M U X H M U X Scenario Years 10 1 1 1 1 1 25 1 1 1 1 50 1 1 1 1 25 1 1 1 1 2 50 1 1 1 1 25 1 1 1 1 3 50 1 1 1 1 25 1 1 1 1 4 50 1 1 1 1 a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b AF 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information. DR Table 7.8. Number of populations of False spike, Texas pimpleback, Texas fatmucket, and Texas fawnsfoot by population conditiona under future scenarios b in the Colorado River watershed. Texas Texas Texas False spike pimpleback fatmucket fawnsfoot H M U X H M U X H M U X H M U X Scenario Years 10 1 1 2 2 1 2 2 1 1 1 1 25 2 2 3 3 2 1 1 50 2 5 2 3 1 1 25 1 1 1 3 1 1 4 1 1 2 50 1 1 3 1 1 2 3 1 1 25 2 2 3 3 2 1 1 3 50 2 5 1 4 1 1 25 2 5 2 3 1 1 4 50 2 5 1 4 2 a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information. Draft Central Texas Mussels SSA Report 125 April 2018 T Table 7.9. Number of populations of False spike and Texas fatmucket by population conditiona under future scenarios b in the Brazos River watershed. Texas False spike fawnsfoot H M U X H M U X Scenario Years 10 1 1 1 1 1 25 1 1 2 50 1 1 2 25 1 1 2 2 50 1 1 1 1 25 1 1 2 3 50 1 1 2 25 1 2 3 4 50 1 1 a AF Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. DR Table 7.10. Number of populations of Texas fawnsfoot by population conditiona under future scenarios b in the Trinity River watershed. Scenario 1 2 3 4 Years 10 25 50 25 50 25 50 25 50 Texas fawnsfoot H M U X 2 2 2 2 2 2 2 2 2 a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information.   Draft Central Texas Mussels SSA Report 126 April 2018 Table 7.11. Conditiona of False spike populations under future scenarios b (See Table 7.1 for more information) in the Guadalupe, Colorado, and Brazos River watersheds. Years Population Watershed 10 25 50 (West to East) (North to South) Scenario Lower Guadalupe Colorado River Lower San Saba Brazos River a M X M M M M X U X X X X X X U U U X U AF Llano 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 M H U U X U X X X X X X U U X X T Guadalupe River Little River U DR Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information. Draft Central Texas Mussels SSA Report 127 April 2018 T AF DR Figure 7.1. Current and projected future resiliency, representation, and redundancy of false spike under all scenarios and time steps. Draft Central Texas Mussels SSA Report 128 April 2018 Table 7.12. Conditiona of Texas fatmucket populations under future scenarios b (See Table 7.1 for more information) in the Guadalupe and Colorado River watersheds. Years Watershed 10 25 50 (West to East) Population (North to South) Scenario Guadalupe River Upper Guadalupe River Colorado River Bluff and Elm Creek U M U U U X X U X X U U U U U M U U U U U X X U X X M AF Llano River U X M X X X U X X U U X X U M U U X U X X X M X X T Upper/Middle San Saba River 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pedernales River Onion Creek U X DR a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information. Draft Central Texas Mussels SSA Report 129 April 2018 T AF DR Figure 7.2. Current and projected future resiliency, representation, and redundancy of Texas fatmucket under all scenarios and time steps. Draft Central Texas Mussels SSA Report 130 April 2018 Table 7.13. Conditiona of Texas fawnsfoot populations under future scenarios b (See Table 7.1 for more information) in the Colorado, Brazos, and Trinity River watersheds. Years Watershed (West 10 25 50 to East) Population (North to South) Scenario Colorado River Lower San Saba River Brazos River Clear Fork Brazos Lower Brazos East Fork Trinity DR Trinity River M X X X X M M M U X U X X X U X X M M M M U M U U U M U U X U AF Upper Brazos X Lower Trinity X U X X U H U X X U X T Lower Colorado 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 M U U X X X X M M U U M U U U M U U a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. b 1: Continuation (of current conditions); 2: (Additional) conservation; 3: RCP 6.0; 4: RCP 8.5. See Table 7.1 for more information. Draft Central Texas Mussels SSA Report 131 April 2018 T AF DR Figure 7.3. Current and projected future resiliency, representation, and redundancy of Texas fawnsfoot under all scenarios and time steps. Draft Central Texas Mussels SSA Report 132 April 2018 Table 7.14. Conditiona of Texas pimpleback populations under future scenarios b (See Table 7.1 for more information) in the Guadalupe and Colorado River watersheds. Years Watershed 10 25 50 (West to East) Population (North to South) Scenario Guadalupe River Upper Guadalupe Colorado River Concho M U U U X M M M M X X X X X U X X U U U X X U X X U M U X X U AF Upper San Saba U X U X X M M U U X X X X X M X X X U X X X M X X X M X X T San Marcos / Lower Guadalupe 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Upper Colorado and Lower San Saba DR Llano Lower Colorado M U M a Healthy (H); Moderately healthy (M); Unhealthy (U); Extirpated / Functional extirpated (X). See Table 5.1 for more information. Draft Central Texas Mussels SSA Report 133 April 2018 T AF DR Figure 7.4. 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Endangered and Threatened Wildlife and Plants; 12-Month finding on a Petition to list Texas Fatmucket, Golden Orb, Smooth Pimpleback, Texas Pimpleback, and Texas Fawnsfoot as Threatened or Endangered. 76FR62166. 48 pp. USFWS. 2015. U.S. Fish and Wildlife Service. USFWS species status assessment framework: an integrated analytical framework for conservation. Version 3.3, dated August 2015. Draft Central Texas Mussels SSA Report A-15 April 2018 USFWS. 2016. U.S. Fish and Wildlife Service. Internal agency email correspondence regarding mussel survey dataset. Received December 12, 2016. 2 pp. USFWS. 2017. U.S. Fish and Wildlife Service. Biologists field notes from mussel surveys in Central Texas. 10 pp. USGS. 1953. U.S. Geological Survey. Noyes Canal, Menard County, Texas Seepage Investigations, May 1920 and July 2, 1853. San Angelo, Texas. 8 pp. USGS. 1998. U.S. Geological Survey Water quality in the Trinity River basin, Texas, 1992-95. Circular 1171. 44 pp. USGS. 1999. 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Report submitted to Texas Department of Transportation. 15 pp. Williams, J.D., M.L. Warren, K.S. Cummings, J.L. Harris, and R.J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22. Williams, J.D., A.E. Bogan, R.S. Butler, K.S. Cummings, J.T. Garner, J.L. Harris, N.A. Johnson, and G.T. Watters. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20:33-58. Willner, S., A. Levermann, F. Zhao, and K. Frieler. 2018. Adaptation required to preserve future high-end river flood risk at present levels. Science Advances 4:eaao1914. 8 pp. T Winemiller, K.O., D.L. Roelke, A. Chin, S.E. Davis, B. Wilcox, and L.M. Romero. 2005. Caddo Lake Annotated Bibliography March 2005. AF Wolaver, B.D., C.E. Cook, D.L. Sunding, S.F. Hamilton, B.R. Scanlon, M.H. Young, X. Xu, and R.C. Reedy. 2014. Potential economic impacts of environmental flows following a possible listing of endangered Texas freshwater mussels. Journal of the American Water Resources Association 1-21. DOI: 10.1111/jawr.12171 Wright, B.H. 1898. A new Unio from Texas. https://biodiversitylibrary.org/page/1746720 The Nautilus 12:93. Available electronically at: Wuebbles, D., G. Meehl, K. Hayhoe, T.R. Karl, K. Kunkel, B. Santer, M. Wehner, B. Colle, E.M. Fischer, R. Fu, A. Goodman, E. Janssen, V. Kharin, H. Lee, W. Li, L.N. Long, S.C. Olsen, Z. Pan, A. Seth, J. Sheffield, and L. Sun. 2013. CMIP5 climate 1 model analyses: climate extremes in the United States. Bulletin of the American Meteorological Society 95:571-583. DR Yeager, M.M., D.S. Cherry, and R.J. Neves. 1994. Feeding and burrowing behaviors of juvenile rainbow mussels, Villosa iris (Bivalvia: Unionidae). Journal of the North American Benthological Society 13:217 222. Draft Central Texas Mussels SSA Report A-17 April 2018 DR AF T APPENDIX B – EVALUATING CAUSES AND EFFECTS OF STRESSORS FOR CENTRAL TEXAS MUSSELS SPECIES STATUS ASSESSMENT Draft Central Texas Mussels SSA Report B- 1 April 2018  Template for Cause and Effects Evaluation For Central Texas Mussels SSA Report THEME: ? [ESA Factor(s): ?] Analysis Confidence / Uncertainty See next page for confidences to  apply at each step. Supporting Information Literature Citations, with page  numbers , for each step. What is the ultimate source of the actions causing the stressor?  ‐ Activity(ies) What is actually happening on the ground as a result of the action? STRESSOR(S) What are the changes in evironmental conditions on the ground that  may be affecting the species?   ‐ Affected Resource(s) What are the resources that are needed by the species that are being  affected by this stressor?   ‐ Exposure of Stressor(s) Overlap in time and space.  When and where does the stressor overlap  with the resource need of the species (life history and habitat needs)?   ‐ Immediacy of Stressor(s) What's the timing and frequency of the stressors? Are the stressors  happening in the past, present, and/or future?   Changes in Resource(s) Specifically, how has(is) the resource changed(ing)? Response to Stressors:   ‐ INDIVIDUALS What are the effects on individuals of the species to the stressor?  (May be by life stage)    POPULATION & SPECIES  RESPONSES Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] [Following analysis will determine how do individual effects translate to population and species‐level responses? And what is the  magnitude of this stressor in terms of species viability?] DR AF T SOURCE(S) What are the effects on population characteristics (lower reproductive  rates, reduced population growth rate, changes in distribution, etc)? ‐ GEOGRAPHIC SCOPE What is the geographic extent of the stressor relative to the range of  the species/populations? In other words, this stressor effects what  proportion of the rangewide populations? What is the geographic extent of the stressor relative to the range of  the species/populations? In other words, this stressor effects what  proportion of the rangewide populations? ‐ MAGNITUDE How large of an effect do you expect it to have on the populations? SUMMARY What is the bottom line‐ is this stressor important to carry forward in  your analysis, or is it only having local effects, or no effects?    ‐ SCOPE Central Texas Mussels Draft SSA Report B‐2 April 2018 This table of Confidence Terminologies explains what we mean when we characterize our confidence levels in the cause and effects tables on the following pages. Highly Confident We are 70 to 90% sure that this relationship or assumption  accurately reflects the reality in the wild as supported by some  available information and/or  consistent with accepted  conservation biology principles. DR Moderately Confident Explanation We are more than 90% sure that this relationship or  assumption accurately reflects the reality in the wild as  supported by documented accounts or research and/or  strongly consistent with accepted conservation biology  principles. AF T Confidence Terminology Somewhat Confident We are 50 to 70% sure that this relationship or assumption  accurately reflects the reality in the wild as supported by some  available information and/or  consistent with accepted  conservation biology principles. Low Confidence We are less than 50% sure that this relationship or assumption  accurately reflects the reality in the wild, as there is little or no  supporting available information and/or  uncertainty  consistency with accepted conservation biology principles.  Indicates areas of high uncertainty. Central Texas Mussels Draft SSA Report B‐3 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment THEME: Increased fine sediment [ESA Factor(s):  A,E] Analysis *Decreased streamflow from reduced precipitation, groundwater extraction, surface withdrawals, and reservoir releases3 *Decreased stream velocities from reduced streamflow and impoundments.  As water velocity decreases, water loses its  ability to carry sediment; which falls to the substrate 5,3,4. *Additional inputs of sediment from streambank erosion from activities in the watershed such as sand and gravel mining,  roads, brush removal, and feral hog activity 4.  SOURCE(S) *Increased scouring in tributaries from large floods leads to sedimentation in rivers 1. 2 *Feral hogs through wallowing in rivers and destabilizing sediments Confidence / Uncertainty Supporting Information Highly confident that these are the primary sources  3Milhous 1998, p. 79 4 of sedimentation for Central Texas mussel  Brim Box and Mossa 1999, p. 100 populations 5 Watters 2000, p. 263 1 Earl (2007) p13 2 Timmons et al. 2011, p. 1 1 Activities that result in increased sedimentation throughout the ranges of the Central Texas mussels include: Environmental changes:  Reduced precipitation; flooding Anthropogenic water demands, development, and mining:  Groundwater extraction for irrigation (row crop agriculture,  municipal use, and oil and gas activities; reservoir construction and operation; reservoir releases; urban/exurban  construction (roads, bridges, and stream crossings, etc.); sand and gravel mining Livestock activity: Grazing/browsing, hoof action.  Runoff from increased impervious surfaces increases sediment loads in  streams and destabilizes stream channels 2. Feral hog activity:  Wallowing and trampling Brush removal: Ashe juniper (Juniperus asheiI ) removal can cause a marked increase in stream sediment1. Sand and gravel mining:   Accelerated streambank erosion and downcutting of streambeds are common effects of instream  sand and gravel mining, as is the mobilization of fine sediments during sand and gravel extraction 3. The removal of sand  AF T ‐Activities Greer 2005, p. 76 Pappas et al. 2008, p. 151 3 Roell 1999, p. 7 4 Simmang and Curran 2006, p. 1 5 USGS 2001, p. 27 2 from within the river creates sediment traps during periods of high flow, which causes scouring and erosion downstream 5.  In addition to headcutting, mines that are located near stream channels are subject to the gravel pit being captured by the  stream during flood events or due to gradual channel migration 4.   Siltation and general sediment runoff is a pervasive problem in streams and has been implicated in the decline of stream  mussel populations3.  Specific biological effects on Central Texas mussels from excessive sediment include reduced feeding  and respiratory efficiency from clogged gills5, disrupted metabolic processes, reduced growth rates, increased substrate  instability, limited burrowing activity 6,7, physical smothering, and disrupted host fish attractant mechanisms 8, smothering of  DR adults and juveniles 1, complete loss of habitat through sedimentation of the crevices inhabited by the species, reduced  juvenile habitat, and increased substrate instability 3,4.  STRESSOR(S) Interstitial spaces (small openings between rocks and gravels) in the substrate provide essential habitat for juvenile  2 mussels .  Fine sediments can lodge between coarser grains of the substrate to form a hardpan layer.   When clogged with  sand or silt, interstitial flow rates and spaces may become reduced, thus reducing juvenile habitat availability and oxygen  permeability2.  Juvenile freshwater mussels burrow into interstitial substrates, making it particularly susceptible to  degradation of this habitat feature 2.    ‐ Affected Resource(s) Highly confident in the relationship between  siltation and freshwater mussels, in general.   Moderately confident that these effects apply  equally to all four species of Central Texas mussels.   Highly confident that crevices completely filled in  with sediment are not suitable habitat for Texas  fatmucket9, 10 1 Watters 2000, p. 263 2 Sparks and Strayer 1998, p. 129 Brim Box and Mossa 1999, pp. 99,  100 3 4 Fraley and Ahlstedt 2000, pp.  193–194 5 Ellis 1936, p. 40 Marking and Bills 1979, pp. 208–209 6 7 Vannote and Minshall 1982, p. 4106 Hartfield and Hartfield 1996, p. 373 8 9  Randklev et al 2017c, p. 40  Howells 2010a, p. 4 10  Juvenile and adult habitat in riffles (False spike, Texas pimpleback, and Texas fawnsfoot) and crevices (Texas fatmucket). Central Texas Mussels Draft SSA Report B‐4 April 2018 Under natural conditions, fine sediments collect on the streambed and in crevices during low flow events, and they are  washed downstream during high flow events (also known as cleansing flows).  However, the increased frequency of low  flow events (from groundwater extraction, surface flow diversions, and drought) combined with a decrease in cleansing  flows (from reservoir management and drought)1 has caused sediment to accumulate to some degree at all populations.   ‐ Exposure of Stressor(s) High confidence in the effects of sedimentation on  freshwater mussels. 1 Milhous 1998, p. 79  Randklev et al 2017c, p. 40  2 3  Howells 2010a, p. 4 Low flows and reduction or elimination of spring flows in the region have been reported for decades.  These locations  experience fine sediment accumulation as a function of low water flow rather than from increased sediment inputs.  Dams  have reduced the number and duration of cleansing flows, such that the channel has aggraded and incised.   Grazing by  livestock (cattle, sheep and goats) is a common practice throughout each of the watersheds, especially in the upper parts of  the basins.  AF T The Texas fatmucket occurs in flowing water dominated with sand, mud, gravel and larger cobbles. The species has also  bene doucmented living in cracks and fissures in larger bedrocks slabs. 2, 3 This species has limited ability to survive low‐flow  events by persiting in deeper pools, with less flow. However, sedementation is more likely to affect lentic environments  instead of lotic areas of the stream.  Historical: The Edwards Plateau watersheds (where soils are naturally highly erodible), including the Guadalupe, Colorado,  and Brazos River watersheds, experienced overgrazing in the past, which was a source of excessive sedimentation. Even in  1959, both the Colorado and Guadalupe Rivers were noted as having high sedimentation rates from agricultural activities 1.  In the Guadalupe River, road crossings were found to cause a long‐term increase in sedimentation both upstream and  downstream, as channel constriction reduced flow upstream, causing sediment deposition, and runoff from the road  increased sedimentation downstream 4.  In the Brazos River, a gravel dredging operation was documented as depositing    ‐ Immediacy of Stressor(s) sediment as far as 1.6 km (1 mi) downstream5. Two sand and gravel mining operations occur in historical habitat for the  Texas fatmucket — the mainstem Colorado River 8 and Johnson Creek9.  Additionally,  two gravel mines along the Colorado  River downstream of Austin were inundated; one by stream channel migration in 1984, one by stream capture in 1991 10. In  1995, the reach of the Guadalupe River near Victoria, which contains a Texas pimpleback population, was described as  having numerous current and abandoned sand and gravel mining areas 13. Current: Agricultural activities and the effects of reservoirs are ongoing in the watersheds. This combined with reduced  cleansing flows has resulted in the accumulation of fine sediments.  All populations are experiencing reduced flood  frequency and duration from drought (exacerbated by climate change; see 3. Loss of Flowing Water for more information  about climate change in this region). Feral hogs are widely distributed in central Texas.  Much of the Brazos River basin is  grazed or farmed for row crops, which can contribute large amounts of sediment to the basin14.  Currently, TPWD has  permitted one sand mining activity within the current range of Texas pimpleback, in the Guadalupe River basin in Comal  County13; a small Texas pimpleback population occurs downstream of this area in the Guadalupe River. Four sand mining  DR activities in the Brazos River basin (Austin, Bosque, and Fort Bend Counties) 15,16,17,18. Turbidity has also been recorded as  high in the Guadalupe River near Victoria 11, indicating a large amount of suspended sediment where a small Texas  pimpleback population was recently found. Historic: Highly confident Current: Highly confident Future: Moderately confident that climate change  will reduce the frequency and duration of cleansing  flows. 1 Soil Conservation Service 1959, pp.  56, 59 2 Gillespie County Soil and Water  Conservation District 2011, p. 1 3 Howells 2010e, p. 6 Keen‐Zebert and Curran 2009, p.  301 4 5 Forshage and Carter 1973, p. 697 TPWD 2008c, p. 1 6 7 TPWD 2008a, p. 1 USACE 2010, p. 2 8 9 TPWD 2007a, p. 1 Simmang and Curran 2006, p. 1 10 11 Exelon 2010, p. 2.3–186 City of San Antonio 2010, p. 5 13 TPWD 2009b , p. 1 14 Brazos River Authority 2007, p. 4 15 TPWD 2004, p. 1 12 16 TPWD 2007b, p. 1 17 TPWD 2008b, p. 1 TPWD 2010b, p. 1 18 Future: Lower flows are expected to occur more often at all populations and for longer periods due to environmental  change combined with surface and ground water withdrawls.  Grazing and oil and gas development are expected to  continue. Sand and gravel mining operations  are permitted near the Texas fatmucket population in Onion Creek 6, and   ‐ Immediacy of Stressors,  continued another in the Llano River watershed in Kimble County 7.  Agriculture is a common land use in the Guadalupe and San  Antonio River basins, and the city of San Antonio, the second largest city in Texas, continues to grow 12. Overall, we expect  fine sediment accumulation to increase at all locations under most conditions. The Texas State Soil and Water Conservation Board has a funding program specifically for Juniperus ashei removal in Blanco,  Gillespie, Kerr, Kendall, and Travis Counties 2, which includes the watersheds of three known Texas fatmucket populations in  Live Oak Creek and the upper Guadalupe River.  In one example,  increased sediment deposition was noted after  widespread Juniperus ashei removal upstream of the Texas fatmucket population in Live Oak Creek 3. Central Texas Mussels Draft SSA Report B‐5 April 2018 Changes in Resource(s) Response to Stressors:   ‐ INDIVIDUALS Substrate suitability for juvenile and adult Central Texas mussels Specific impacts on juvenile and adult mussels from silt and sediments include clogged gills, which reduce feeding and  High confidence respiratory efficiency, impair reproductive activity, disrupt metabolic processes, and reduce growth rates;  and the physical  smothering of mussels under a blanket of silt 1,2. 1 Sparks and Strayer 1998, p. 129 Brim Box and Mossa 1999, pp. 99,  100 2    POPULATION & SPECIES  RESPONSES Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] Some levels of sedimentation may be tolerated by Central Texas mussels, as the lower reaches of the rivers inhabited by the  Moderately confident species are relatively turbid and silt‐laden (except in the case of Texas fatmucket).  However, when enough sediment is  deposited into the cracks and crevices in which Central Texas mussels are found, they become smothered and die.  If this  occurs over a long enough time and over enough of the inhabited reach, resiliency would be reduced. Moderately confident AF T Decreased Streamflow is expected to occur across the range of all four species of Central Texas mussels due to the  combined effects of drought due to climate change, decreased groundwater, and the effects of reservoir operations. 1  Bonner et al p. 242‐3, 266 Increased Scour has occured a multiple locations, primarily lower in the basins. For example, in 2017 a large diverse  ‐ GEOGRAPHIC SCOPE mussel community in the lower Colorado River (near Altair, Texas) was almost completed eliminated due to flooding scour  associated with Hurricane Harvey 1. Currently, all populations are experiencing  fine sediment accumulation such that substrate quality is affected.  ‐ MAGNITUDE DR SUMMARY Sediment accumulation is a pervasive problem throughout the range of Central Texas mussels. Sediment accumulation in the substrates occupied by Central Texas mussels has reduced habitat availability for all four  species historically and is expected to continue into the future.  This stressor will be carried forward in our analysis of future  conditions of the species. Central Texas Mussels Draft SSA Report B‐6 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment THEME: Changes in water quality  ‐ Activity(ies) DR SOURCE(S) Analysis Confidence / Uncertainty Changes in water quality parameters such as dissolved oxygen, salinity, total suspended solids,  High confidence increased temperature, and contaminants.  Sources of these changes include: Low dissolved oxygen:  Slow moving, warm water generally has low dissolved oxygen levels  relative to the needs of the species.  Additionally, high amounts of nutrients, such as nitrogen  and phosphorus, in streams can stimulate excessive plant growth (algae and periphyton, among  others), which in turn can reduce dissolved oxygen levels when dead plant material  decomposes. Salinity: In the Upper Brazos River,and in the Upper Colorado, saline springs and seeps in the  watershed contribute chlorides to the river2. Increased temperature: Drought and increased air temperature due to climate change (and low  flows and pooling result in water temp increases) degradation of riparian habitat (loss of  shading) contributes to increased water temps6. Total suspended solids: Sedimentation and increased organic matter. Contaminants: Point sources, such as spills, septic system leaks, and wastewater treatment  plants, and non‐point sources, such as agricultural and urban runoff, and uplanned releases  during major floods.  These sources contribute ammonia, organic compounds, heavy metals,  pesticides, bacteria, herbicides, nutrients, and a wide variety of newly emerging contaminants to  the aquatic environment. Sources of ammonia include agricultural activities (animal feedlots and  nitrogenous fertilizers), septic systems, municipal wastewater treatment plants and urban  runoff, and industrial waste,  as well as precipitation and natural processes (decomposition of  organic nitrogenous compounds)3,4,5.  Metals occur in industrial and wastewater effluents and  are often a result of atmospheric deposition from industrial processes and incinerators. Supporting Information 3 Augsperger et al. 2003, p. 2569 Newton 2003, p, 2543 5 Augsperger et al. 2007, pp. 2025, 2026 6 Mantua et al 2010, p. 196 1 Timmons et al 2011, p.1 2 Baker et al 1964 p. CC1 4 AF T [ESA Factor(s):  A,E] Low dissolved oxygen: wastewater discharge, groundwater extraction, climate change High confidence Salinity: Natural contributions (and petroleum extraction) from upstream tributaries in upper  Brazos River and far upper Colorado watershed3. Total suspended solids: See "Increased fine sediment" analysis for a full description of the  activites that result in increased total suspended solids (TSS). Increased temperature: Groundwater extraction, climate change, land use change (riparian  habitat degradation)4,5,6. Contaminants: Tanker truck and other spills7, wastewater treatment plant outfalls8, industrial  sources, municipal effluents, and agriculture runoff.  Ammonia may be particularly high  downstream of wastewater treatment plant discharges2. Activities related to septic systems  near the rivers, municipal wastewater discharge, agricultural wastewater discharge may cause  NH3‐N contamination.  Feral hog activity (and livestock, exotic deer) in a watershed can increase  levels of bacteria, nutrients through defecation in and near a river.1 Central Texas Mussels Draft SSA Report B‐7 2 Augsperger et al. 2003, p. 2569 Strayer et al 2004, p. 436 5 Mace and Wade 2008, p. 656 6 Mantua et al 2010, p. 196 7 Jones et al 2001 8 Gillis et al 2014 1 Timmons et al 2011 p. 1 3 Chowdhury et al. 2010 p. 36 4 April 2018 STRESSOR(S) Chemical contaminants:  The release of pollutants into streams from point and nonpoint  sources have immediate impacts on water quality conditions and may make environments  unsuitable for habitation by mussels11. Early life stages of freshwater mussels are some of the  most sensitive organisms of all species to ammonia and copper1,7,10, with mortality occurring at  levels lower than current EPA criteria8.  Additionally, sublethal effects of contaminants over time  can result in reduced filtration efficiency, reduced growth, decreased reproduction, changes in  enzyme activity, and behavioral changes to all mussel life stages8,11,12.  Even wastewater  discharges with low ammonia levels have been shown to negatively affect mussel populations11.  Mussels are also affected by metals13  such as cadmium, chromium, copper, mercury, and zinc,  which can negatively affect biological processes such as growth, filtration efficiency, enzyme  activity, valve closure, and behavior13,1,14,15. Water quality Freshwater mussels may close their valves to avoid short‐term exposure to poor water quality or  Moderately confident contaminants, but metabolic needs force the mussels to begin siphoning after about 24 hours1.   Newly transformed juveniles and not yet encysted glochidia are the most sensitive life stage to  poor water quality and contaminants.2 DR   ‐ Affected Resource(s) AF T Low dissolved oxygen: Juveniles are particularly susceptible to low dissolved oxygen levels,  Moderately confident although adult metabolism levels are lower in areas of lower dissolved oxygen.  Juveniles will  reduce feeding behavior between 2 ‐ 4 mg/L, and mortality has been shown to occur at levels  below 1.3 mg/L3.  Salinity: Juvenile mussels of other species have been shown to experience complete mortality  after 7 days at levels greater than 4 ppt5,11. Total suspended solids: Total suspended solids profoundly affect mussel reproduction through  direct interference with fertilization of eggs2,6. Increased temperature: Glochidial release may be associated with water temperature;  increased stream temperature may cause the timing of release to change4.  Depending the  degree of change in temperature, this could cause species/host interactions to be out of sync9.   Increased water temperature can also exacerbate other water quality problems, such as the  effects of contaminants (by causing thermal stress to individuals).   ‐ Exposure of Stressor(s) Central Texas Mussels Draft SSA Report B‐8 1 Naimo 1995, pp. 351–352 Sparks and Strayer 1998, pp. 129, 132 4 Watters and O'Dee 2000, p. 136 5 Blakeslee et al 2013, p. 2851 6 Strayer et al. 2004, p. 436 7 Cherry et al. 2005, p. 378 8 Augsperger et al 2007, p. 2025 9 Spooner and Vaughn 2008, p. 313 10 Gillis et al 2010, p. 2519 11 Gillis 2012, p. 354 12 Gillis et al 2014, p. 3 2 Gascho‐Landis et al. 2013 p. 76 13 Keller and Zam 1991 p 543 14 Jacobson et al. 1997, p. 2390 15 Valenti et al. 2005, p. 1244 3 1 Cope et al 2008, p. 453 Cope et al 2008, p. 456, 458 2 April 2018 2 Mace and Wade 2008, p. 656 CNorthwestlimate toolbox, p. 1 USGS 1999 3 Cihock 2011, p. 1 4 TCEQ 2010a, p. 294 5 Bramlette and Cosel 2010, p. 1 6 MacCormack 2011, p. 1 7 Lee and Schultz 1994, p. 8 8 Associated Press 1991, p. 1 9 Joiner 2010, p. 1 1 AF T   ‐ Immediacy of Stressor(s) Low dissolved oxygen: High summer temperatures cause low dissolved oxygen to currently  Moderately confident occur, and the incidence will increase as climate change causes lower water levels2.  Salinity: The upper Brazos River watershed has had documented high salinity due to naturally  saline seeps and springs in the basin.  Decreased water levels due to climate change and water  withdrawals may cause the salinity concentrations to increase. Total suspended solids: High TSS levels are occuring currently in locations with high turbidity. Increased temperature: In the short term, Central Texas mussels may be exposed to high  temperatures when water levels drop during drought.  Pools with no or little water flow increase  in temperature.  Over time, the average high air temperature is expected to increase by 2  degrees F in 20 years and 5.5 degrees F in 50 years1, drought will occur more often, and so  Central Texas mussels will be exposed to high temperatures more often. Contaminants: There is a history of water quality impairment and contamination throughout the  basins: the Trinity River historically experienced very poor water quality before the advent of  modern sanitation, there a 1961 DDT spill in Town Lake on the Colorado River, and  contamination has been assoicated with major floods like Hurricane Harvey, lots of bacteria  impairments (Leon, others). Spills from on‐site accidents (e.g. tank and pipeline spills) have occurred within the historical  ranges of the Central Texas mussels. For example, 450 gallons of oil were spilled into Lake  Bastrop, a reservoir on a tributary to the Colorado River, in February 20113. As much as 320,000  L (84,000 gal) of crude oil was spilled in the Brazos River in 19918.  In June 2010, flooding of  holding ponds adjacent to oil drilling operations leaked oil into Thompson Creek and  subsequently into the Brazos River.  Also, in July 2010, oil pipelines burst and released  approximately 165 barrels of crude oil into the upper Brazos River9. DR Within the range of Central Texas mussels, high ammonia levels are common, either chronically,  such as in Elm Creek, which is listed as impaired due to high ammonia concentrations4, or due to  spills.  A wastewater leak in August 2010 spilled approximately 380,000 liters (L) (100,000 gallons  (gal)) of sewage into Elm Creek5; ammonia is present in high concentrations in sewage, among  other pollutants.  Additionally, a sewage spill in 2008 in Onion Creek discharged nearly 380,000 L  (100,000 gal), and another sewage spill occurred in April 2011 in Quinlan Creek, a tributary to  the Guadalupe River6. High copper concentrations have been recorded in fish in the lower Guadalupe River and San  Antonio River7. Changes in Resource(s) Water becomes less suitable or unsuitable. Central Texas Mussels Draft SSA Report B‐9 April 2018    POPULATION & SPECIES  RESPONSES Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] ‐ MAGNITUDE SUMMARY 1 Havlik and Marking 1987, p. 13 Sparks and Strayer 1998, pp. 129, 132 3 Watters and O'Dee 2000, p. 136 4 Spooner and Vaughn 2008, p. 313 5 Blakeslee et al 2013, p. 2851 2 Populations in areas affected by changed water quality parameters can be eliminated. Low dissolved oxygen: Low dissolved oxygen is most likely to occur in reaches with low water  Moderately confident levels and/or sources of effluent. The Hill Country tributaries to the Colorado River, the Colorado  River mainstem near Colorado Bend State Park, and the Colorado River downstream of Austin,  Texas could be sussceptible to low oxygen availability due to either low flows and increased  temperature or waste water effluent. Upper stretches of the Brazos River near Possum Kingdom  reservoir and north of Waco could experience low dissolved oxygen due to low flows.  Salinity: The upper Brazos River basin (and Upper Colorado) is affected by high salinity, and we  expect this to continue into the future. With decreased flows the effects of eleveated sality  increase. Increased temperature: Temperatures are expected to increase more in small streams that are  more vulnerable to low water levels. Contaminants: Ammonia concentrations increase with increasing temperature and low‐flow  conditions, which may be exacerbated during low‐flow events in streams1,2.  1 Cherry et al. 2005, p. 378 Cooper et al. 2005, p. 381 2 DR ‐ GEOGRAPHIC SCOPE AF T Response to Stressors:   ‐ INDIVIDUALS Moderately confident Low dissolved oxygen: Adults and juveniles reduce activity and ultimately die2. Salinity:   Overall, freshwater mussels cannot live fore extended periods in saline waters.  Juvenile Elliptio complanata  have been shown to experience complete mortality after 7 days at  4 ppt5. Increased temperature: Individuals exposed to high temperatures may experience thermal  stress.  This generally occurs at temperatures over 40 degrees C, for thermally tolerant species.   If this exposure lasts for more than a short period, individuals may die4.  Increased water  temperatures may also affect the timing of glochidial release3. Contaminants:  Ammonia, chlorine, and copper are particularly toxic to juvenile mussels1.  Glochidia also appear to be very sensitive to certain toxicants, such as heavy metals. Even at low  levels, certain heavy metals, such as copper, may inhibit glochidial attachment to fish hosts. This threat is significant for mussels inhabiting smaller, more headwater streams. We believe  these episodic low‐flow events during drought are a natural phenomenon experienced by the  species but has been exacerbated by alluvial pumping, agriculture and municipal water needs.  Freshwater mussels are particularly sensitive to water quality impairment.  Poor water quality  has  reduced habitat availability for all four species historically and is expected to continue into  the future.  This stressor will be carried forward in our analysis of future conditions of the  species. Central Texas Mussels Draft SSA Report B‐10 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment [ESA Factor(s):  A,E] SOURCE(S) THEME:  Altered Hydrology ‐ Inundation Analysis Confidence / Uncertainty Reservoir construction and operation High confidence Large and small impoundments STRESSOR(S)   ‐ Affected Resource(s) Moderately confident The Central Texas Mussels generally do not inhabit reservoirs or ponded areas,  likely due to smothering by deposited sediment and the lack of use of that habitat  by host fish.  In large reservoirs, deep water is very cold and often devoid of oxygen  1 and necessary nutrients .  Cold water (less than 11 °C (52 °F)) has been shown to  stunt mussel growth.  Because mussel reproduction may be tied to temperature, it  is likely that individuals living in the constantly cold hypolimnion in these channels  2,3 may never reproduce, or reproduce less frequently .  Cold water releases  downstream of dams may also preclude reproduction. Water and, as water velocity slows, substrate Moderately confident Dam construction in Texas began in 1890 with Miller Dam on the Colorado River  1 near Austin .  Over 100 major reservoirs (> 5,000 ac/ft) were constructed in Texas  before 19601.  Texas now has 188 major reservoirs and numerous river diversions 5.   Since that time, 27 major reservoirs have been constructed in the Brazos basin 2, 19  in the Colorado River basin 3, and two large reservoirs and 6 smaller reservoirs in the  Guadalupe River basin 4.  These reservoirs have fragmented habitat for Central  Texas mussels, as none of these species occur in reservoirs, and habitat  downstream of dams is unsuitable due to temperature and hydrological impacts. DR  ‐ Exposure of Stressor(s) High confidence AF T ACTIVITY Historically, reservoirs are the primary cause of habitat loss for the Central Texas  Highly confident mussel species and drive their current distribution. Future projects are planned,  1 such as Cedar Ridge Reservoir on the Clear Fork Brazos River , within the range of  3 Texas fawnsfoot . This reservior would most likely have a detrimental effect, if not  copletley extirpate the Clear Fork of the Brazos Texas fawnsfoot population.    ‐ Immediacy of Stressor(s) Supporting Information 1 Hanson et al. 1988, p. 352 Watters 2000, p. 264 3 Watters and O’Dee 2000, p. 455 2 Dean and Schmidt 2011, pp. 4, 6 Carter et al 2015, p. 15 1 Carter et al 1964, pp. 3‐8 2 TWDB 2018a, pp. 2‐4 3 TWDB 2018b, pp. 2‐3 TWDB 2018c, p. 2 5 TWDB 2017, p. 62 4 1 USACE 2016, p. 2 Howells 1997a, p. 36, 71 3 HDR Engineering, 2011 p. 2,3 2 In one area on the Guadalupe River in Kerr County, a Texas fatmucket population  2 once existed directly below a small dam , indicating the effects of the dam  construction and closure were not immediately lethal.  However, the population  2 has been presumed extirpated since 1998 , and it is likely that fluctuating  downstream flows from the dam contributed to the loss of this population. Central Texas Mussels Draft SSA Report B‐11 April 2018 Response to Stressors:   ‐ INDIVIDUALS    POPULATION & SPECIES  RESPONSES BIO‐WEST 2018 p.1 Populations in areas affected by inundation can be eliminated. DR Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] 1 AF T Changes in Resource(s) Water resources in reservoirs are generally unsuitable for Central Texas mussel  High confidence species, which require flow.  Additionally, inundation can cause large amounts of  sediment to be deposited in the mussel bed, eliminating suitable habitat for the  mussels.   High confidence Texas pimpleback, Texas fawnsfoot, and false spike: Individuals in inundated  reaches will likely not reproduce.  Those smothered with deposited sediment will  die.  Texas fatmucket: Some Texas fatmucket are able to tolerate, persist, and  reproduce in small in‐channel impoundments (i.e. above lowhead dams) that retain  characteristics of free‐flowing streams and may provide for low‐flow refugia (pools)  during droughts (Llano Park Lake  was completed in 1958; Kerrville Ponding Dam  was completed in 1980), but not in similar but larger impoundments like Llano City  1 Lake that result in more of a reservoir‐type (lentic) environment . This species has  adapted to persiting in pools as it utilizes naturally forming pool areas in streams to  persist during low flow events.  Central Texas Mussels Draft SSA Report B‐12 April 2018 Dams have been built throughout the range of the Central Texas mussels, especially  Moderately confident on the larger river systems (Brazos, Colo, Guad), fragmenting populations and  eliminating habitat above and below each major impoundment. TWDB 2018a, b, c ‐ GEOGRAPHIC SCOPE AF T Brazos River: There are 27 major reservoirs in the Brazos River basin2.  The Brazos  River Authority (BRA) owns and operates 3 reservoirs Possum Kingdom (on the  Brazos River), Grandbury (on the Brazos River) and Limestone (on the Navasota  River).  The BRA has water contracts for and the US Army Corps of Engineers  operates Whitney (on the Brazos River), Proctor and Belton (on the Leon River),  Stillhouse Hollow (on the Lampasas River), Georgetown and Granger (on the San  Gabriel River), Somerville (on Yegua Creek), and Aquilla (on Aquilla Creek). Colorado River (and Hill Country tributary rivers): There are 19 major reservoirs in  the Colorado River basin3 ), including the 6 Highland Lakes that supply water to the  Austin, Texas metro area.  Guadalupe River: There are 2 major reservoirs in the Guadalupe River basin,  Canyon (a cold water release hydropower reservoir build in 1964) and Coleto Creek  (a cooling plant reservoir), and 6 smaller reservoirs managed by GBRA that are  located between Canyon and Coleto Creek. Cold water releases below Canyon Dam on the Guadalupe River likely preclude  Central Texas Mussels. low temps, low DO, algal blooms. The other major dams are  designed more for flood protection, recreation, and water supply and do not  release water from the hypolimnion. DR The current condition and range of all four Central Texas mussel species was greatly  formed by reservoir construction and operation, and these effects are expected to  continue into the future. Historically, reservoirs drove the distribution of the Central Texas mussels,  fragmenting ranges, preventing genetic exchange, and preventing recolonization  after stochastic events.  These effects continue to affect the status of all four  species into the future. ‐ MAGNITUDE SUMMARY Central Texas Mussels Draft SSA Report B‐13 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment [ESA Factor(s):  A,E] AF T SOURCES THEME:  Altered Hydrology ‐ Flow Loss and Scour Analysis Confidence / Uncertainty Effects of climate change such as drought, flood/scour from very large rainfall  High confidence events, heat waves, and increase evapotranspiration Anthropogenic water demands such as groundwater extraction and surface water  diversion Construction projects River dewatering may be used to expedite construction  activities. Climate change is likely to result in more extreme flooding and droughts and lead  High confidence 4 to changes in surface water, soil moisture, and groundwater .  Effects of climate  change and anthropogenic water demands, in combination, cause reduced  5 baseflow; reduced groundwater recharge and spring flows , increased  evapotranspiration, and increased frequency and duration of drought. Increased human populations in Texas result in an increase municipal water  demand. Groundwater extraction and surface water diversions result in reduced  5  groundwater recharge and spring flows and reduced baseflow, resulting in at least  partial stream drying.  Additionally, water use for oil and gas production 6 and shale‐ gas production (such as Eagle Ford shale in the Guadalupe River basin) can result in  lowered base flows. ACTIVITY Stream drying:  Mussels can tolerate short periods of time out of water.  If the  Moderately confident stream is not completely dry but has very low flow, they may be able to close their  valves until conditions improve.  However, as low flows persist, they face oxygen  1  TWDB 2017, p. 3 TWDB 2017, p. 6 3  TWDB 2017, p. 78 4 Talyor et al. 2013, entire 5 Niraula et al 2017 2  6 Arciniega‐Esparza et al 2017 1 Watters 2000, p. 264 2 Golladay et al. 2004, p. 501 Galbraith et al 2010 p. 1180 3 DR deprivation, increased water temperature, and, ultimately, stranding 2,3. Supporting Information STRESSORS  ‐ Affected Resources Scour: Freshwater mussels require stable substrates in which to anchor. Extreme  rainfall events that scour habitats occupied by the Central Texas mussels can  dislodge the mussels from their habitats, depositing them downstream.   Additionally, sediments entrained by the high flow events may then be deposited  1 on the substrate inhabited by the species, if they did not get dislodged . Water and, as water velocity slows, substrate Central Texas Mussels Draft SSA Report B‐14 April 2018 Stream drying can affect individuals at all life stages. Because anthropogenic water  Moderately confident demand is high at the same time availability is low, Central Texas mussels will be  more vulnerable to dyring during dry seasons. 1 Randklev et al 2017, p. 13, 110, 137 1 Texas fawnsfoot occurs in riverbanks . Because of this, they may be stranded even  when water levels do not drop to levels low enough to expose the stream bottom.    ‐ Exposure of Stressors Moderately confident Stream drying: As with many areas of North America, the range of the Central  Texas Mussels is projected to experience an overall warming trend over the next 50  8,9,10 . Although precipitation models vary substantially, with some even  to 100 years predicting increased precipitation annually, a consensus is emerging that  evaporation rates are likely to increase significantly, and annual runoff is expected  to decrease in Texas by 10 to 30 percent. Many models are also predicting that  seasonal variability in flow rates is likely to increase with more precipitation  occurring in the wet seasons and more extended dry periods, with a greater  likelihood for more extreme droughts. Drought is also expected to increase in  frequency and magnitude due to climate change.  Heat waves and extreme  4 precipitation events are expected to become more intense and frequent .   Temperatures in the state of Texas have increased by an average of 2 degrees  1 Fahrenheit since the 1970s . One preliminary study forecasting the possible  hydrological impacts of climate change on the annual runoff and its seasonality in  the upper Colorado River watershed was conducted by CH2M HILL (2008).  In this  initial evaluation, four modeling scenarios (chosen to represent a range of possible  future climatic conditions) were each run under a 2050 and 2080 time scenario,  producing annual surface water runoff estimates at multiple sites with stream  gages in the Colorado River basin.  For the 2050 scenarios, the results from all four  climate change scenarios predicted significant decreases in annual runoff totals  9 compared to historic averages  .  DR  ‐ Immediacy of Stressors AF T 1 False spike and Texas pimpleback occur in riffles and shallow bank habitat .  Riffles,  by definition, are less deep than pools, and therefore experience drying or very low  river levels before pools.  Species found in these habitats are more susceptable to  dessication when drying occurs. Central Texas Mussels Draft SSA Report B‐15 8 Nohara et al. 2006, p. 1087 CH2M HILL 2008, p. 6‐4 9 10 Mace and Wade 2008, p. 656 StateImpact 2014, pp. 1, 2 2 Nicot and Scanlon 2012, p. 3584 1 3 TWDB 2017 p 36 IPCC 2014 p. 10 5 NOAA 2018, p. 6 4 6 Geeslin et al 2015 Arciniega‐Esparza et al 2017, p. 170 7 8 Howells 1999, pp. 18–19 9 CH2M HILL 2008, pp. 7‐30–7‐32 Bonner et al, p. 242‐3, 266 10 April 2018 Effects of climate change are only expected to increase into the future as droughts  become more frequent and air temperatures increase, resulting in more  groundwater extraction.  The Texas human population is expected to increase by  more than 70% between 2020 and 2070 (from 29.5 to 51 million) and water  demands are expected to increase by 17% during the same period (from 18.4 to  21.6 million acre feet per year1 with the largest increase resulting from municipal  2 demands ; State Water Plan considers a 50‐year horizon; by 2070, municipal water  3 users are expected to make 38% of the state's water needs . AF T Dessication and subsequent mussel death due to drought occured throughout the  range of Central Texas mussels in 2011, which was the driest year on record for  1,3 Texas . Intensity of water use in the Eagle Ford Shale has likely peaked and is  expected to decrease 2. 2011‐2015 drought evident in the Colorado River at Garwood.  *2015 drought  6 low/no flow in San Saba River ‐ recent dead observed .  ‐ Immediacy of stressors,  continued Reductions in baseflow due to hydraulic fracturing ("fracking") water withdrawals  were observed in the Gualupe River basin, but were masked and exacerbated by  the 2011‐2012 drought and by other consumptive uses of groundwater (i.e., ag  7 irrigation and urban demand . DR In 2017, Hurricane Harvey was the most significant rainfall event in U.S. history 5.  Flooding occured throughout Central Texas. In the lower Colorado River near Altair,  Texas, significant changes in both mussel community structure and bathymetry  10 occured during extensive flooding in August 2017, as a result of Hurricane Harvey .  This reach previously held the highest mussel abundance of the Lover Colorado  River and represented high quality habitat within the Colorado basin, prior to these  10 flooding events . Survey results indicated a significant decrease in mussel  abundance on the scale of nearly two orders of magnitude 10. This location had two  of the Central Texas mussels (Texas fawnsfoot and Texas pimpleback) present  10 during initial surveys in 2017 . Rivers can also be dewatered to expedite construction activities, which happened in  the upper Guadalupe River in Kerr County in 1998 for bridge construction;  8 numerous Texas fatmuckets were exposed and desiccated (dried out and died) . Central Texas Mussels Draft SSA Report B‐16 April 2018 Changes in Resources Stream drying: A completely dry streambed eliminates habitat for the Central Texas  High confidence mussels.  Lowered flows can cause stagnant pools to form, which over a period of  time can become unsuitable for mussels as water temperatures increase and  dissolved oxygen decreases.  Low water levels for a short period of time may be  endured periodically, but over the long term mortality of mussels can be similar  between reaches that are completely dry or those that remain wetted at very low  1 flow . 1 Haag and Warren 2008, p. 1173 AF T Scour: Mussels may become dislodged and deposited downstream in unsuitable  habitat.  Additionally, sediment being carried downstream may be deposited on  mussel beds as velocities slow. Stream drying: Mussels in dry reaches will become desiccated.  Those in reaches  with very low flow may experience temperature stress and the effects of low  dissolved oxygen.  If the condition persists, they will likely die. Response to Stressors:   ‐ INDIVIDUALS    POPULATION & SPECIES  RESPONSES Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] High confidence Scour: Individuals deposited downstream will likely die. Those smothered with  deposited sediment will die. Populations in areas affected by loss of flowing water can be eliminated. Moderately confident 1 Niraula et al 2017 DR Groundwater recharge is expected to be reduced in the future throughout the  range of the Central Texas mussels 1.    ‐ GEOGRAPHIC SCOPE Currently, groundwater pumping and surface diversions are not high enough to  show significant effects to populations of Central Texas mussels, except perhaps in  portions of the San Saba River.  However, pumping and diversions, could  exacerbate drought effects.  Further, future increases in pumping and diversions  could further reduce flow in river reaches occupied by Central Texas Mussels. ‐ MAGNITUDE Flow loss and scour are having large effects on Central Texas mussels throughout  their ranges, and these effects are expected into the future. SUMMARY Flow loss, stream drying, and scour are expected to continue to affect Central Texas  mussel species into the future due to the combined effects of climate change and  increased human demand for water.  These effects will be carried forward in our  analysis of  effects to Central Texas mussels into the future. Central Texas Mussels Draft SSA Report B‐17 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment THEME: Predation, Collecting, Disease and Invasive Species SOURCE(S)  ‐ Activity(ies) Confidence / Uncertainty As stream flows decline, access by terrestrial predators increases, causing  higher mortality to the population than would otherwise be experienced. Collection and sampling of rare species at known sites can impact  population sizes. High confidence   ‐ Affected Resource(s)   ‐ Exposure of Stressor(s) Supporting Information 1 Edelman et al. 2015 1 *Predation on freshwater mussels is a natural ecological interaction.   Moderate confidence that zebra  TPWD 2018, p. 1 2 Raccoons, snapping turtles, and fish are known to prey upon Central Texas  mussels will continue to infest  Strayer and Malcom 2007, pp.  mussels.  Under natural conditions, the level of predation occurring within  reservoirs in the BCG  111,118 populations is not likely to be a significant risk to that population.   basins...uncertain of the magnitude of  However, during periods of low flow, terrestrial predators have increased  effect on Central Texas Mussels in the  access to portions of the river that are generally too deep under normal  future. flow conditions.  Muskrats and raccoons are known to prey upon live  mussels, as evidenced by freshly fragmented valves strewn along vegetated  riverbank margins. *Invasive zebra mussels are now introduced in the Brazos, Colorado, and  Guadalupe River basins1. Zebra mussels can affect water quality and  compete for food and dissolved oxygen2. *Collection for scientific studies removes animals from the reproducing  population and, if a population is repeatedly visited for samples, can have a  negative effect on the population. DR STRESSOR Analysis *Increased terrestrial predation from American mink, northern raccoon,  northern river otter, and common muskrat1. *increased competition/negative interactions with exotic invasive species *Overcollection at certain locations AF T [ESA Factor(s): C] *Predation, Collection: Individuals are killed. *Invasive species compete for resources. As stream flows decline, access by terrestrial predators increases,  increasing predation rates by raccoons and muskrats1. Adults are more  susceptible to predation and collection than juveniles, as they are larger  and easier to find. High confidence High confidence 1 Golladay et al 2004, p. 503 Zebra mussels have not been found co‐occuring with Central Texas mussel  populations yet, but may in the future. Central Texas Mussels Draft SSA Report B‐18 April 2018 Mortality due to predation have been observed during low flow periods.   Somewhat confident Raccoons have preyed on individual Texas fatmuckets stranded by low  waters or deposited in shallow water or on bars following flooding or low  water periods2 As drought and low flow are predicted to occur more often  and for longer periods due to climate change, the san Saba River and other  hill country rivers are expected to experience additional predation pressure  in the future. Collection is occurring currently at multiple locations across the known  range of the Central Texas mussels. For example, in 2017 seven Texas  fatmucket, ten false spike, seventy Texas fatmucket, and nintey six Texas  pimplebacks were removed from across eight sites in the Brazos, Colorado  and Guadalupe Rivers3. While these animals were utilized for scientific  research, many of the sites sampled in 2017 are easily accessed and often  collected from by other individuals for other research interests.  AF T   ‐ Immediacy of Stressor(s)  1Howells 2004, p. 7 Howells 2010c, p. 12 3 Bonner et al 2018, p. 159 2 Commercial harvest impacted populations in the past. No live unionids  (native freshwater mussels) were reported from Elm Creek or from the  Colorado River near Ballinger, Texas, in August 2003; pearl harvesters had  previously reported that exhaustive collecting had occurred at these sites1. Zebra mussels are currently found in all rivers occupied by Central Texas  mussels, although they occur in reservoirs not occupied by Central Texas  mussels.  High confidence Mussels preyed upon or collected die.  Mussels competing for resources  may have lower fitness and reproductive output, and overall the population  may decline. High confidence Mussels preyed upon or collected die.  Mussels competing for resources  may have lower fitness and reproductive output, and overall the population  may decline. DR Changes in Resource(s) Response to Stressors:   ‐ INDIVIDUALS    POPULATION & SPECIES  RESPONSES Central Texas Mussels Draft SSA Report B‐19 April 2018 Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] Predation on freshwater mussels is a natural ecological interaction.  Otters,  High confidence raccoons, snapping turtles, and fish are known to prey upon Texas  hornshell.  Under natural conditions, the level of predation occurring within  Central Texas mussels populations is not expected to be a significant risk.   However, populations that are already at risk from low flow conditions  during drought are further affected by increased access by terrestrial  predators.  Populations experiencing this combination of low flow and high  predation have less resiliency and a higher risk of extirpation than those  not experiencing those pressures. AF T Populations experiencing overcollection will continue to decline. At this time, we do not expect zebra mussels to affect Central Texas mussel  population resiliency, due to the habitat used by zebra mussels. The upper portions of the watersheds (Hill Country Rivers of the Colorado  High confidence River Basin) as well as the upper Brazos and upper Guadalupe are more  susceptible to low flow events and, therefore, increased predation levels,  compared with the lower reaches. In the larger, mainstem rivers (Trinity,  Brazos, Colorado, and Guadalupe) there is some concern of increased  predation risk with low flow events as all of the Central Texas mussels  inhabitat areas prone to dewatering.  Collection occurs potentially range wide for all Central Texas mussels.  However, it is of particular concern in the Hill Country tributaries to the  Colorado River and to some extent the populations on the lower Guadalupe  River. The Trinity and Braozs Rivers seem less impacted by collection and  scientific research activites as these areas are typically more remote, and  require more specialized equipment to access (e.g. scuba/boat).  DR ‐ GEOGRAPHIC SCOPE ‐ MAGNITUDE Predation is an exacerbating factor on populations already experiencing  stress due to low flows, and the additional mortality reduces resiliency.   Overcollection has a large impact at certain populations, but not  rangewide.  Zebra mussels are not expected to have a large impact. SUMMARY Predation and collection are expected to continue to exacerbate poor  habitat conditions at Central Texas mussel populations into the future  These effects will be carried forward in our analysis of  effects to Central  Texas mussels into the future.  Zebra mussels will not be carried forward in  our analysis. Central Texas Mussels Draft SSA Report B‐20 April 2018 Evaluating Cause and Effects for Central Texas Mussels Species Status Assessment THEME: Barriers to fish movement [ESA Factor(s): A] SOURCE(S)  ‐ Activity(ies) Analysis Dams, diversions, reservoirs Dam construction, water withdrawals, flood control Confidence / Uncertainty High confidence High confidence 1 Hoffman et al. 2017 pp. 2, 8‐9 Watters 1996, pp. 80, 83 3 Turner et al 2000, p. 783 4 Berg et al 2007, pp. 1436 ‐1437  2 Population fragmentation:  Dam construction fragments the range of  Central Texas Mussels, leaving remaining habitats and populations isolated  by the structures as well as by extensive areas of deep uninhabitable,  impounded waters. Dams impound river habitats throughout almost the  entire range of the species, and these impoundments have left isolated  patches of remnant habitat between impounded reaches. Multiple  tributary streams draining into the Brazos, Colorado and Guadalupe River  bains drain directly into mainstem river impoudnments and are isolated  from other populations of mussels. Fragmented populations are susceptible  to genetic drift (change of gene frequencies in a population over time), and  inbreeding depression3,4. Inbreeding depression can result in death,  decreased fertility, smaller body size, loss of vigor, reduced fitness, and  various chromosomal abnormalities1,3.  DR STRESSOR(S) AF T Change in distribution and abundance of mussels:  The overall distribution  High confidence  of mussels is a function of the dispersal of their hosts. The distributions of  the fragile papershell (Leptodea fragilis ) and pink heelsplitter (Potamilus  alatus ) in five midwestern rivers have been limited by the presence of low‐ head dams2.  These dams were non‐navigable (without locks), lacked fish  ladders, and varied in height from 1 to 17.7 m (3 ft to 58 ft), and the host  fish could not disperse through them2. The multiple dams throughout the  range of Central Texas species in the Trinity, Brazos, Colorado and  Gudalupe River basins have fragmented their ranges in a similar way.  Supporting Information Host fish abundance: recruitment is generally positively related to host fish  High confidence abundance, although the relationship may be nonlinear1.   1 Haag and Stoeckel 2015   ‐ Affected Resource(s) Populations that are extirpated due to other, stochastic events can not be  recolonized due to isolation from previously connected reaches.   ‐ Exposure of Stressor(s)   ‐ Immediacy of Stressor(s) There are 48 large dams in the Brazos, Colorado, and Guadalupe River  basins, affecting the gene flow and resiliency of existing populations.  High confidence Large dams have been in existence since the mid 1900s, (generally between  High confidence the 1930s and 1960s ‐ some as recently as 1980s) fragmenting the range of  Central Texas Mussels since that time. Central Texas Mussels Draft SSA Report B‐21 National Dam Inventory April 2018 Response to Stressors:   ‐ INDIVIDUALS    POPULATION & SPECIES  RESPONSES Effects of Stressors:   ‐ POPULATIONS      [RESILIENCY] ‐ GEOGRAPHIC SCOPE ‐ MAGNITUDE Moderately confident Population resiliency is decreased if isolation results in such genetic  Moderately confident isolation that genetic drift occurs. We do not currently expect that Central  Texas mussel population resiliency has been affected, where they currently  occur.  However, if populations are extirpated they will not be recolonized  naturally High confidence Overall, within the Brazos, Colorado and Guadalupe River bains each  species of Central Texas mussel is experiencing population fragmentation  due to impoundments and dams. However, the degree of isolation varies  by species and by basin.  Population fragmentation due to barriers to fish movement has had a large  High confidence effect on all four Central Texas mussel species historically.  Currently, and  into the future this fragmentation reduces the ability of all populations to  rebound from stochastic events. We do not expect fragementation to get worse into the future.  We will  carry forward the historical effects of fragmentation on the four Central  Texas mussel species, but we will not vary the magnitude of this stressor in  future scenarios. DR SUMMARY Habitat fragmentation acts on the population level. Individuals are  unaffected. AF T Changes in Resource(s) Host fish are unable to travel between Central Texas mussel populations,  High confidence isolating existing populations from one another. Genetic exchange between  populations has been eliminated, and any populations that may be  extirpated through stochastic events will not be naturally recolonized. Central Texas Mussels Draft SSA Report B‐22 April 2018 APPENDIX C ‐ FUTURE CONDITION TABLES FOR CENTRAL TEXAS MUSSELS C.1. FALSE SPIKE C.1.A SCENARIO 1 Table C.1. False spike population conditions under Scenario 1 (Continuation) in 10 years. Colorado Population Lower San Saba Llano Guadalupe Brazos Lower Guadalupe Little AF T Basin False Spike- Scenario 1, 10 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Func. Ext. Overall Condition Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Unhealthy Moderate Moderate Moderate Unhealthy Healthy Unhealthy Unhealthy Table C.2. False spike population conditions under Scenario 1 (Continuation) in 25 years. DR False Spike- Continuation Scenario 1, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Basin Colorado Guadalupe Brazos Population Overall Condition Lower San Saba Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Lower Guadalupe Healthy Healthy Moderate Moderate Moderate Moderate Moderate Little Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Draft Central Texas Mussels SSA Report C- 1 April 2018 Table C.3. False spike population conditions under Scenario 1 (Continuation) in 50 years. Colorado Guadalupe Brazos Population Overall Condition Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Guadalupe Little C.1.B SCENARIO 2 AF T Basin False Spike- Continuation Scenario 1, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Healthy Healthy Unhealthy Unhealthy Moderate Moderate Unhealthy Unhealthy Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Table C.4. False spike population conditions under Scenario 2 (Conservation) in 25 years. Basin Lower San Saba Moderate Unhealthy Unhealthy DR Colorado Population False Spike- Continuation Scenario 2, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Guadalupe Brazos Overall Condition Moderate Moderate Moderate Unhealthy Llano Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Lower Guadalupe Healthy Healthy Moderate Moderate Moderate Moderate Moderate Little Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Draft Central Texas Mussels SSA Report C- 2 April 2018 Table C.5. False spike population conditions under Scenario 2 (Conservation) in 50 years. Colorado Population Lower San Saba Llano Guadalupe Brazos Lower Guadalupe Little C.1.C SCENARIO 3 Overall Condition Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Healthy Healthy Healthy Moderate Moderate Moderate Healthy Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy AF T Basin False Spike- Scenario 2, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Table C.6. False spike population conditions under Scenario 3 (RCP 6.0) in 25 years. False Spike- Scenario 3, 25 years Population Factors Population Abundance Reproduction Habitat Factors Flowing Water Substrate Water Quality DR Basin Stream Length Colorado Guadalupe Brazos Overall Condition Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Guadalupe Healthy Healthy Moderate Moderate Little Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Draft Central Texas Mussels SSA Report C- 3 Moderate Moderate Moderate April 2018 Table C.7. False spike population conditions under Scenario 3 (RCP 6.0) in 50 years. False Spike- Scenario 3, 50 years Population Factors Population Lower San Saba Colorado Guadalupe Brazos Llano Lower Guadalupe Little C.1.D SCENARIO 4 Abundance Reproduction Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Healthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. AF T Basin Habitat Factors Flowing Water Substrate Water Quality Stream Length Overall Condition Table C.8. False spike population conditions under Scenario 4 (RCP 8.5) in 25 years. False Spike- Scenario 4, 25 years Population Factors DR Abundance Reproduction Habitat Factors Flowing Water Substrate Water Quality Basin Colorado Guadalupe Brazos Stream Length Population Overall Condition Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Guadalupe Healthy Moderate Moderate Moderate Little Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Draft Central Texas Mussels SSA Report C- 4 Moderate Moderate Moderate April 2018 Table C.9. False spike population conditions under Scenario 4 (RCP 8.5) in 50 years. False Spike- Scenario 4, 50 years Population Factors Population Lower San Saba Colorado Guadalupe Brazos Llano Lower Guadalupe Little C.2. TEXAS FATMUCKET Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. DR C.2.A SCENARIO 1 Abundance Reproduction AF T Basin Habitat Factors Flowing Water Substrate Water Quality Stream Length Overall Condition Table C.10. Texas fatmucket population conditions under Scenario 1 (Continuation) in 10 years. Basin Colorado Guadalupe Population Texas Fatmucket – Scenario 1, 10 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Elm Creek Unhealthy Unhealthy Unhealthy Moderate Unhealthy Unhealthy Unhealthy San Saba Healthy Moderate Moderate Moderate Moderate Moderate Moderate Llano Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Pedernales Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Unhealthy Func. Ext. Guadalupe Unhealthy Unhealthy Unhealthy Moderate Moderate Draft Central Texas Mussels SSA Report C- 5 Moderate Unhealthy April 2018 Table C.11. Texas fatmucket population conditions under Scenario 1 (Continuation) in 25 years. Colorado Guadalupe Population Overall Condition Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Llano Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Pedernales Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Unhealthy Func. Ext. Guadalupe Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Texas Fatmucket – Scenario 1, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition AF T Basin Texas Fatmucket – Scenario 1, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate DR Table C.12. Texas fatmucket population conditions under Scenario 1 (Continuation) in 50 years. Basin Colorado Guadalupe Population Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Llano Moderate Unhealthy Unhealthy Moderate Pedernales Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Unhealthy     Draft Central Texas Mussels SSA Report C- 6 April 2018       C.2.B SCENARIO 2 Table C.13. Texas fatmucket population conditions under Scenario 2 (Conservation) in 25 years. Colorado Guadalupe Population AF T Basin Texas Fatmucket – Scenario 2, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Elm Creek Unhealthy Unhealthy Unhealthy Moderate San Saba Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Llano Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Pedernales Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Onion Creek Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Guadalupe Moderate Unhealthy Moderate Moderate Moderate Unhealthy Elm Creek Texas Fatmucket – Scenario 2, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Unhealthy Unhealthy Unhealthy Moderate Unhealthy Moderate Overall Condition Unhealthy San Saba Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Pedernales Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Onion Creek Guadalupe Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Moderate Unhealthy Unhealthy Moderate Overall Condition Unhealthy DR Table C.14. Texas fatmucket population conditions under Scenario 2 (Conservation) in 50 years. Basin Colorado Guadalupe Population Llano   Draft Central Texas Mussels SSA Report C- 7 April 2018     C.2.C SCENARIO 3 Table C.15. Texas fatmucket population conditions under Scenario 3 (RCP 6.0) in 25 years. Colorado Guadalupe Population Overall Condition AF T Basin Texas Fatmucket – Scenario 3, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Llano Healthy Unhealthy Unhealthy Moderate Pedernales Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Guadalupe Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Moderate Unhealthy Table C.16. Texas fatmucket population conditions under Scenario 3 (RCP 6.0) in 50 years. DR Basin Colorado Guadalupe   Texas Fatmucket – Scenario 3, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Population Overall Condition Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Pedernales Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext.   Draft Central Texas Mussels SSA Report C- 8 April 2018     C.2.D SCENARIO 4 Table C.17. Texas fatmucket population conditions under Scenario 4 (RCP 8.5) in 25 years. Colorado Guadalupe Population Overall Condition AF T Basin Texas Fatmucket – Scenario 4, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Llano Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Pedernales Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext.   Table C.18. Texas fatmucket population conditions under Scenario 4 (RCP 8.5) in 50 years. DR Basin Colorado Guadalupe   Texas Fatmucket – Scenario 4, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Population Overall Condition Elm Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Pedernales Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Onion Creek Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext.   Draft Central Texas Mussels SSA Report C- 9 April 2018   C.3. TEXAS FAWNSFOOT C.3.A SCENARIO 1 Table C.19. Texas fawnsfoot population conditions under Scenario 1 (Continuation) in 10 years. Brazos Colorado Trinity Population Overall Condition AF T Basin Texas Fawnsfoot – Scenario 1, 10 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Healthy Unhealthy Unhealthy Unhealthy Unhealthy Moderate Unhealthy Lower Brazos Healthy Moderate Moderate Moderate Moderate Moderate Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Moderate Func. Ext. Lower Colorado Healthy Moderate Healthy Moderate Moderate Moderate Moderate East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Unhealthy Unhealthy Moderate Unhealthy Unhealthy Healthy Table C.20. Texas fawnsfoot population conditions under Scenario 1 (Continuation) in 25 years. DR Texas Fawnsfoot – Scenario 1, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Basin Brazos Colorado Trinity Population Overall Condition Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Lower Brazos Moderate Moderate Moderate Moderate Moderate Moderate Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Moderate Func. Ext. Lower Colorado Healthy Moderate Moderate Unhealthy Unhealthy Unhealthy Moderate East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Moderate Moderate Moderate Unhealthy Unhealthy Healthy   Draft Central Texas Mussels SSA Report C-10 April 2018     Table C.21. Texas fawnsfoot population conditions under Scenario 1 (Continuation) in 50 years. Brazos Colorado Trinity Population Overall Condition Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Lower Brazos Moderate Moderate Moderate Moderate Moderate Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Moderate Moderate Moderate Unhealthy Texas Fawnsfoot – Scenario 2, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition   C.3.B SCENARIO 2 AF T Basin Texas Fawnsfoot – Scenario 1, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Unhealthy Moderate Moderate DR Table C.22. Texas fawnsfoot population conditions under Scenario 2 (Conservation) in 25 years. Basin Brazos Colorado Trinity Population Clear Fork Brazos Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Upper Brazos Healthy Unhealthy Unhealthy Unhealthy Unhealthy Moderate Unhealthy Lower Brazos Healthy Moderate Moderate Moderate Moderate Moderate Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Moderate Func. Ext. Lower Colorado Healthy Moderate Healthy Moderate Moderate Moderate Moderate East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Moderate Moderate Moderate Unhealthy Unhealthy Moderate Healthy   Draft Central Texas Mussels SSA Report C-11 April 2018 Table C.23. Texas fawnsfoot population conditions under Scenario 2 (Conservation) in 50 years. Brazos Colorado Trinity Population Clear Fork Brazos Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Lower Brazos Healthy Moderate Moderate Moderate Healthy Moderate Moderate Lower San Saba Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Lower Colorado Healthy Healthy Moderate Moderate Moderate Healthy East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Moderate Moderate Moderate Unhealthy Texas Fawnsfoot – Scenario 3, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition   C.3.C SCENARIO 3 Moderate Overall Condition AF T Basin Texas Fawnsfoot – Scenario 2, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Healthy Unhealthy DR Table C.24. Texas fawnsfoot population conditions under Scenario 3 (RCP 6.0) in 25 years. Basin Brazos Colorado Trinity Population Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Lower Brazos Moderate Moderate Moderate Moderate Moderate Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Moderate East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Unhealthy Moderate Moderate Unhealthy Unhealthy Moderate Moderate   Draft Central Texas Mussels SSA Report C-12 April 2018 Table C.25. Texas fawnsfoot population conditions under Scenario 3 (RCP 6.0) in 50 years. Brazos Colorado Trinity Population Overall Condition Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Lower Brazos Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy East Fork Trinity Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Trinity Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Texas Fawnsfoot – Scenario 4, 25 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition   C.3.D SCENARIO 4 AF T Basin Texas Fawnsfoot – Scenario 3, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Func. Ext. DR Table C.26. Texas fawnsfoot population conditions under Scenario 4 (RCP 8.5) in 25 years. Basin Brazos Colorado Trinity Population Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Lower Brazos Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy East Fork Trinity Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Trinity Healthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Moderate Func. Ext.   Draft Central Texas Mussels SSA Report C-13 April 2018 Table C.27. Texas fawnsfoot population conditions under Scenario 4 (RCP 8.5) in 50 years. Brazos Colorado Trinity Population Overall Condition Clear Fork Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Brazos Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Lower Brazos Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Lower San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. East Fork Trinity Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Trinity Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy   C.4. TEXAS PIMPLEBACK C.4.A SCENARIO 1 Func. Ext. AF T Basin Texas Fawnsfoot – Scenario 4, 50 years Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Table C.28. Texas pimpleback population conditions under Scenario 1 (Continuation) in 10 years. DR Texas pimpleback – Scenario 1, 10 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Basin Colorado Population Concho Colorado & San Saba Upper San Saba Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Llano Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Lower Colorado Guadalupe Upper Guadalupe San Marcos & Lower Guadalupe Draft Central Texas Mussels SSA Report C-14 April 2018   Table C.29. Texas pimpleback population conditions under Scenario 1 (Continuation) in 25 years. Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba Moderate Unhealthy Unhealthy Moderate Moderate Moderate Moderate AF T Basin Texas Pimpleback – Scenario 1, 25 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Moderate Func. Ext. Lower Colorado Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Upper Guadalupe San Marcos & Lower Guadalupe Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Moderate Table C.30. Texas pimpleback population conditions under Scenario 1 (Continuation) in 50 years. DR Texas Pimpleback – Scenario 1, 50 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Basin Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Guadalupe San Marcos & Lower Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Healthy Moderate Moderate Moderate Moderate Moderate Moderate   Draft Central Texas Mussels SSA Report C-15 April 2018   C.4.B SCENARIO 2 Table C.31. Texas pimpleback population conditions under Scenario 2 (Conservation) in 25 years. Colorado Population Concho Colorado & San Saba Upper San Saba Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Llano Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Lower Colorado Guadalupe Upper Guadalupe San Marcos & Lower Guadalupe AF T Basin Texas Pimpleback – Scenario 2, 25 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Table C.32. Texas pimpleback population conditions under Scenario 2 (Conservation) in 50 years. DR Texas Pimpleback – Scenario 2, 50 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Basin Colorado Population Concho Colorado & San Saba Upper San Saba Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Unhealthy Moderate Moderate Moderate Moderate Moderate Moderate Llano Unhealthy Moderate Moderate Unhealthy Moderate Moderate Moderate Healthy Moderate Moderate Moderate Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Lower Colorado Guadalupe Upper Guadalupe San Marcos & Lower Guadalupe   Draft Central Texas Mussels SSA Report C-16 April 2018   C.4.C SCENARIO 3 Table C.33. Texas pimpleback population conditions under Scenario 3 (RCP 6.0) in 25 years. Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba AF T Basin Texas Pimpleback – Scenario 3, 25 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Upper Guadalupe San Marcos & Lower Guadalupe Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Healthy Moderate Moderate Moderate Moderate Moderate Moderate Table C.34. Texas pimpleback population conditions under Scenario 3 (RCP 6.0) in 50 years. DR Texas Pimpleback – Scenario 3, 50 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Basin Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Guadalupe San Marcos & Lower Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Healthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Draft Central Texas Mussels SSA Report C-17 April 2018 C.4.D SCENARIO 4 Table C.35. Texas pimpleback population conditions under Scenario 4 (RCP 8.5) in 25 years. Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba AF T Basin Texas Pimpleback – Scenario 4, 25 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Guadalupe San Marcos & Lower Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy   Moderate Table C.36. Texas pimpleback population conditions under Scenario 4 (RCP 8.5) in 50 years. DR Texas Pimpleback – Scenario 4, 50 years Population Factors Habitat Factors Stream Flowing Water Overall Length Abundance Reproduction Substrate Water Quality Condition Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Basin Colorado Guadalupe Population Concho Colorado & San Saba Upper San Saba Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Llano Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Lower Colorado Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Upper Guadalupe San Marcos & Lower Guadalupe Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy   Draft Central Texas Mussels SSA Report C-18 April 2018 APPENDIX D– RESULTS BY POPULATION Freshwater mussels, as a taxonomic group in North America, have faced a multitude of threats including: habitat destruction, reduced access to host fish, commercial exploitation, and introduced species (Bogan 1993, pp. 603-5). The Central Texas mussels are vulnerable to each those “big-picture” stressors, but are also subject to the following stressors, in particular: (reviewed in detail of Chapter 6, this report). Increased fine sediment Changes in water quality Altered hydrology: inundation Altered hydrology: flow loss and scour Predation, collection, disease, and invasive species Barriers to fish movement affecting access to affiliate species of host fish T       AF Additionally, there is the potential that positive management actions can be made to improve the current and future population conditions of the Central Texas mussels. While there is high certainty that climate effects have and will continue to occur, some uncertainty remains in the relative magnitude of these effects (i.e., “intermediate” versus “severe”). What is constant in the climate change predictions is enhanced evaporative demand (i.e., overall drying) and that precipitation patterns will become more “extreme.” DR Important uncertainties relevant to the future condition of identified populations include: erosion and sediment dynamics associated with development patterns, climate change effects on stream inputs and outputs (through evapotranspiration and other losses), changes to hydrology due to the effects of increasing climate extremes and management actions, human responses to decreased inputs and increased outputs, construction of reservoirs and wastewater treatment plants, return flows and reuse, development of alternative water supplies, and effects of invasive species, among others. This appendix contains summaries of the results of the status assessment by the population of each species. For specific discussion of how the stressors act upon the species, see Chapter 6 (Factors Influencing Viability) and Appendix B (Cause and Effects Tables), and for discussion of details of each scenario and the specific activities occurring in each major river basin, see Chapter 7 (Viability and Future Conditions). D.1 FALSE SPIKE False spike is currently represented by two populations in the Colorado River basin, one population in the Guadalupe River basin, and one population in the Brazos River basin. The currently unhealthy Lower San Saba River population (Table D.1) will continue to be threatened by very low habitat occupancy, low abundances, and a lack of reproduction and subsequent recruitment, despite the currently moderately healthy substrate, water quantity, and water quality conditions, and is expected to become functionally extirpated in the next 10 years. Future degradation of habitat factors is expected as flows continue to be diminished by climate forcings, most notably altered precipitation Draft Central Texas Mussels SSA Report E-1 April 2018 patterns (dewatering droughts and scouring floods) combined with enhanced evaporative demands, and anthropogenic withdrawals to support existing and future demands for municipal and agricultural water. Because reduced flows and other hydrologic alterations exacerbate the effects of and interact with impaired substrate and water quality, each of the three habitat factors is expected to become unhealthy in 50 years. Some conservation actions could improve the viability of this population somewhat if implemented in the next 10 years. These actions include measures to maintain and improve the status quo conditions of the habitat factors, through habitat restoration and flows management. Improvements to the Brady, Texas wastewater treatment plant (currently underway) could have a combination of positive and negative effects to the downstream mussels. Presumably the new plant would be discharging larger volumes of effluent, increasing the anthropogenic influences of the hydrology of the Lower San Saba River, with uncertain effects on water quality and sediment dynamics. False Spike: Lower San Saba River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality AF Scenario T Table D.1. Projection of false spike population conditions in the Lower San Saba River currently and in 50 years under four future scenarios. Moderate Current Moderate Unhealthy Unhealthy Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Moderate Unhealthy Unhealthy Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Unhealthy Unhealthy DR Moderate Moderate Overall Condition The currently unhealthy Llano River population (Table D.2) will continue to be threatened by low habitat occupancy, low abundances, and low reproduction and subsequent recruitment, despite the currently moderately healthy substrate, water quantity, and water quality conditions, and is expected to become functionally extirpated in the next 25 years. Future degradation of habitat factors is expected as flows continue to be diminished by climate forcings, most notably altered precipitation patterns (dewatering droughts and scouring floods) combined with enhanced evaporative demands, and anthropogenic withdrawals to support existing and future demands for municipal and agricultural water. Likewise, the currently small population will become smaller as older individuals leave the population and new individuals fail to recruit into the population, as evidenced by an apparent lack of reproduction. Because reduced flows and other hydrologic alterations exacerbate the effects of and interact with impaired substrate and water quality, each of the three habitat factors is expected to become unhealthy in 50 years. Given the limited spatial extent of this population, low population size, and apparent lack of reproduction provide little hope that conservation actions could improve the viability of this population somewhat if implemented in the next 50 years. This population, due to ease of access to the location, is especially vulnerable to the threat of over-collection and vandalism. We expect this population to be extirpated in 50 years under all scenarios. Draft Central Texas Mussels SSA Report E-2 April 2018 Table D.2. Projection of false spike population conditions in the Llano River currently and in 50 years under four future scenarios. Scenario False Spike: Llano River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Current Unhealthy Unhealthy Unhealthy Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Func. Ext. Func. Ext. Func. Ext. Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Unhealthy Func. Ext. T Moderate Moderate Overall Condition DR AF The currently moderately healthy Lower Guadalupe (Table D.3) population will continue to be resilient to degradation of habitat factors, due to healthy abundances, large amount of occupied habitat, and evidence of reproduction and recruitment, and is expected to become unhealthy in 50 years only in Scenarios 3 and 4, where flows become diminished somewhat under increasingly severe climate scenarios. In all other cases, this population remains moderately healthy or healthy in 50 years due to a combination of habitat and demographic factors. Some conservation actions could improve the viability of this population somewhat if implemented in the next 10 years. These actions include measures to maintain and improve the status quo conditions of the habitat factors, through habitat restoration, flows management, and continued improvements to water quality. Additional opportunities for enhanced resiliency exist in the form of possible “mussel-friendly” improvements to the Guadalupe Valley Electric Cooperative string of dams above this population. Continued flow protections, afforded by the EAHCP, contribute substantially to the resiliency of this population. For as long as stream flows provide much of the base flow to the Lower Guadalupe River, this population will be relatively resilient to climate forcings, compared to the other river systems that lack this subsidized base flow. Table D.3. Projection of false spike population conditions in the Lower Guadalupe River currently and in 50 years under four future scenarios. Scenario False Spike: Lower Guadalupe River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Healthy Moderate Moderate Moderate Moderate Moderate Scenario 1 Healthy Healthy Moderate Moderate Unhealthy Unhealthy Moderate Scenario 2 Healthy Healthy Healthy Moderate Moderate Scenario 3 Healthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 4 Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Draft Central Texas Mussels SSA Report E-3 Moderate Healthy April 2018 T The currently unhealthy Little River population (Table D.4) is expected to remain unhealthy in 25 years, becoming functionally extirpated in 50 years under Scenarios 3 and 4. Habitat factors are expected to decline to unhealthy in 25 years, because of alterations to flows and water quality associated primarily with increasing development in the watershed as the Austin metropolitan area continues to expand. Climate forcings remain a concern that is mediated somewhat by the likelihood that enhanced return flows associated with the development and use alternative water supplies will bolster base flows somewhat. The boost from return flows will likely be limited by the need for reuse and additional water conservation in 50 years. Because of the relatively small size of the Little River basin, some conservation actions could improve the viability of this population somewhat if implemented in the next 10 years. These actions include measures to maintain and improve the status quo conditions of the habitat factors, through habitat restoration, flows management, and continued improvements to water quality. For example, it may be possible to manage releases from Belton, Stillhouse, and Granger Lakes to provide flows to benefit this population. Further, opportunities may exist to restore and enhance riparian and adjacent upland habitats in the watershed. Table D.4. Projection of false spike population conditions in the Little River currently and in 50 years under four future scenarios. AF Scenario False Spike: Little River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Unhealthy Unhealthy Moderate Scenario 1 Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 2 Moderate Unhealthy Unhealthy Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. DR Current Scenario 4 Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Overall Condition Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Func. Ext. In Scenario 1, within 50 years, the Lower San Saba River and Llano River populations are projected to become functionally extirpated, the Lower Guadalupe River population would be moderately healthy, and the Little River population would be unhealthy. In both Scenario 3 and 4, only the unhealthy Lower Guadalupe River population would remain extant, in 50 years. D.2 TEXAS FATMUCKET Texas fatmucket is currently represented by five populations (including one believed to be functionally extirpated) in the Colorado River basin and by one population in the Guadalupe River basin. The currently unhealthy Elm Creek population (Table D.5) is expected to become functionally extinct in the next 50 years in all future scenarios except for Scenario 2 where the population is maintained at status quo unhealthy conditions through implementation of positive soil and water conservation measures in the relatively small and agriculturally dominated watershed of Elm Creek. The population will continue to be Draft Central Texas Mussels SSA Report E-4 April 2018 threatened by existing unhealthy amount of occupied stream length and unhealthy low population abundance and unhealthy low levels of reproduction and subsequent recruitment into the population. Likewise, habitat factors in all but the most optimistic scenario are considered to be unhealthy because of excessive sedimentation and deterioration of substrate, altered hydrology associated with anthropogenic activities and climate forcing, and water quality impairment. Because of the relatively small size of the watershed, some opportunities exist to engage agricultural producers and municipal users in improving water quality, and perhaps water quantity in the watershed. However, because this population is small in terms of occupied stream miles and is hydrologically isolated from larger populations, it will likely never be more resilient than unhealthy. Table D.5. Projection of Texas fatmucket population conditions in Elm Creek currently and in 50 years under four future scenarios. T Scenario Texas Fatmucket: Elm Creek Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Unhealthy Unhealthy Unhealthy Moderate Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Unhealthy Unhealthy Moderate Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. AF Current Moderate Unhealthy DR The currently moderately healthy San Saba River population (Table D.6) is expected to become unhealthy or functionally extirpated in the next 50 years, depending on the influence of climate change over the next 25+ years. The San Saba River population is threatened by habitat degradation in the form of excessive sedimentation, reduced flows due to anthropogenic influences and climate forcing, and water quality impairment primarily associated with low flows. Because of the complex geology of the San Saba River, certain sections of the river are considered “losing reaches” that are especially sensitive to reductions in flow associated with pumping and drought. In fact, this “losing stretch” of the river is subject to repeated drying and is dependent on the lower “gaining reaches” reaches for recolonization following a prolonged drought. There is some evidence that Texas fatmucket can persist at low levels in pools and in crevices for some length of time during a dewatering event. However, available habitat is limited during prolonged low flow conditions, which are almost certain to occur with increasing frequency in the future. Reductions in available habitat due to dewatering also make mussels more vulnerable to predation. Some mussel beds within this population, due to ease of access, are vulnerable to the threat of over-collection and vandalism. Draft Central Texas Mussels SSA Report E-5 April 2018 Table D.6. Projection of Texas fatmucket population conditions in the San Saba River currently and in 50 years under four future scenarios. Scenario Texas Fatmucket: San Saba River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Moderate Moderate Moderate Moderate Scenario 1 Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 2 Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate T Moderate AF The currently moderately healthy Llano River population (Table D.7) is expected to become unhealthy, in the next 50 years under scenarios 1, 3 and 4, as population factors including abundance decline due to unhealthy reproductive conditions and over-collection. Declining flows in scenarios 3 and 4 results in unhealthy habitat factors, compounding the effects of currently unhealthy reproduction conditions. In Scenario 2, population factors are improved through adaptive management of collection, and moderately healthy habitat factors are maintained through voluntary programs and management of pumping during drought to mitigate against severe dewatering events. This population, due to ease of access to the location, is especially vulnerable to the threat of over-collection and vandalism. DR Table D.7. Projection of Texas fatmucket population conditions in the Llano River currently and in 50 years under four future scenarios. Scenario Texas Fatmucket: Llano River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Moderate Unhealthy Moderate Moderate Moderate Moderate Scenario 1 Moderate Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 2 Healthy Moderate Moderate Moderate Moderate Moderate Moderate Scenario 3 Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 4 Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy The currently unhealthy Pedernales River population (Table D.8) is expected to become functionally extinct in the next 50 years in all scenarios except for Scenario 2, in which current habitat and population factors are maintained through conservation actions. This population will continue to be threatened by unhealthy population factors, generally in terms of low abundance and low reproduction and subsequent recruitment of individuals into the population. This population will also be influenced by future Draft Central Texas Mussels SSA Report E-6 April 2018 development near Fredericksburg, as well as by continuing and exacerbated climate forcings. The Pedernales River is a flashy system, especially in the lower reaches in the vicinity of Pedernales Falls State Park, and below. Regardless, give the current low observed abundances and hydrologic isolation from other larger populations, this population is not expected to be very resilient now or into the future. Table D.8. Projection of Texas fatmucket population conditions in the Pedernales River currently and in 50 years under four future scenarios. Scenario Texas Fatmucket: Pedernales River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Unhealthy Unhealthy Moderate Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Moderate Unhealthy Unhealthy Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate T Moderate Moderate Unhealthy AF Moderate DR The currently functionally extirpated Onion Creek population (Table D.9) is expected to remain functionally extirpated in the next 50 years in all scenarios except for Scenario 2, which assumes that the habitat factors can be improved somewhat by habitat enhancement in the watershed, by water quality protections as the watershed develops, and by restoration of populations by repatriation of hatchery-reared individuals. Given that Texas fatmucket has apparently been extirpated from Onion Creek, and it is hydrologically isolated from any other population, repatriation using hatchery-produced stock in Onion Creek may be appropriate if the habitat can be restored. Scenario 2 assumes that Texas fatmucket can be restored to Onion Creek and that Onion Creek can be managed through partnerships with the City of Austin, private landowners, and other interested parties. Given the spatial extent of Onion Creek, and its isolation, it is expected that the population will remain functionally extirpated without positive conservation that could ultimately result in a moderately healthy managed population in 50 years. Draft Central Texas Mussels SSA Report E-7 April 2018 Table D.9. Projection of Texas fatmucket population conditions in Onion Creek currently and in 50 years under four future scenarios. Scenario Texas Fatmucket: Onion Creek Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Overall Condition Current Func. Ext.  Func. Ext.  Func. Ext.  Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Moderate Moderate Moderate Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate T Moderate Unhealthy Func. Ext. AF The currently unhealthy Guadalupe River population (Table D.10) is expected to become functionally extirpated in the next 50 years due to a combination of population and habitat factors, most notably low abundances and risks of low flow events due to drought. This population is likely very dependent on maintenance of base flows thorough groundwater (i.e., spring) influences. Scenario 2 includes some positive conservation actions that could possibly increase the resiliency of the population to moderately healthy after 50 years. (Note: This population may, in fact, represent a species other than Texas fatmucket.) Table D.10. Projection of Texas fatmucket population conditions in the Guadalupe River currently and in 50 years under four future scenarios. DR Texas Fatmucket: Guadalupe River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Scenario Moderate Current Moderate Unhealthy Unhealthy Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Moderate Moderate Moderate Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Overall Condition Moderate Unhealthy Moderate In summary, after 50 years and assuming Scenario 1 conditions, four of the six populations are expected to become functionally extirpated while the remaining two populations would be unhealthy.     Draft Central Texas Mussels SSA Report E-8 April 2018 D.3 TEXAS FAWNSFOOT Texas fawnsfoot is currently represented by 3 populations in the Brazos River basin, 2 populations in the Colorado River basin, and 2 populations in the Trinity River basin. T The currently unhealthy Clear Fork of the Brazos River population (Table D.11) is threatened by unhealthy population factors, namely low abundance, and low reproduction, and by unhealthy habitat factors. This population likely experienced extensive mortality associated with prolonged dewatering during the 2011-13 drought combined with ambient water quality impairments associated with naturally occurring elevated salinity levels from the upper reaches of the river. This population is likely functionally extirpated, although more survey effort may be needed to reach that conclusion. Further, the proposed Cedar Ridge Reservoir, if constructed, will likely result in significant hydrologic alterations, all of which would not be expected to improve the overall condition of this population of Texas fawnsfoot. This population is not expected to be resilient in the future, regardless of scenario. Scenario AF Table D.11. Projection of Texas fawnsfoot population conditions in the Clear Fork of the Brazos River currently and in 50 years under four future scenarios. Texas Fawnsfoot: Clear Fork Brazos River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Unhealthy Unhealthy Moderate DR Current Moderate Moderate Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. The currently unhealthy Upper Brazos River population (Table D.12) is similarly threatened by low abundances and lack of reproduction, and by reduced flows associated with drought, anthropogenic actions and by current and future climate forcings, and by water quality impairments associated with naturally-occurring salinity. Under all scenarios, this population is expected to become functionally extirpated in the next 50 years, principally due to unhealthy abundance and reproduction factors. This population is not expected to be resilient in the future, regardless of scenario. Draft Central Texas Mussels SSA Report E-9 April 2018 Table D.12. Projection of Texas fawnsfoot population conditions in the Upper Brazos River currently and in 50 years under four future scenarios. Overall Condition Current Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Scenario 2 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Moderate Func. Ext. T Scenario Texas Fawnsfoot: Upper Brazos River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality DR AF The currently moderately healthy Lower Brazos River population (Table D.13) generally benefits from having a moderately healthy habitat occupancy, as well as observed moderately healthy abundance and evidence of reproduction and recruitment. Likewise, habitat factors are moderately healthy to healthy, likely because of the lack of major impoundments and diversions in the Brazos River below Waco, Texas. In the next 50 years, assuming Scenario 1 or Scenario 2 conditions, this population remains moderately healthy. In Scenarios 3 and 4, the population declines to an unhealthy condition as anthropogenic activities interact with additional climate forcings, and the Lower Brazos River becomes more utilized for municipal and other needs. Because Texas fawnsfoot occupies primarily bank habitats in this system, even small reductions in flows can reduce water elevations such that bank habitats become dewatered or otherwise exposed to predation, sedimentation, and elevated water temperatures. This habitat affinity may also make this population vulnerable to the threat of sand and gravel mining in the lower reaches of this segment. The planned Allen’s Creek off-channel reservoir is located near an especially abundant location of Texas fawnsfoot, and construction and subsequent operation of this reservoir are not expected to improve the condition of this population. While this system is apparently fairly resilient, Texas fawnsfoot has yet to be collected in abundance. Regardless, Texas fawnsfoot is not currently found in high abundances in the Lower Brazos River, and future habitat degradation will likely reduce the resiliency of this population. Draft Central Texas Mussels SSA Report E-10 April 2018 Table D.13. Projection of Texas fawnsfoot population conditions in the Lower Brazos River currently and in 50 years under four future scenarios. Overall Condition Current Healthy Moderate Moderate Moderate Healthy Moderate Moderate Scenario 1 Moderate Moderate Moderate Moderate Moderate Moderate Moderate Scenario 2 Healthy Moderate Moderate Moderate Healthy Moderate Moderate Scenario 3 Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 4 Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy T Scenario Texas Fawnsfoot: Lower Brazos River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality AF The currently unhealthy Lower San Saba River population (Table D.14) is subject to unhealthy population factors, namely low abundance and apparent lack of reproductive success and subsequent recruitment of new individuals to the population. Habitat factors are currently unhealthy overall, due primarily to degraded substrate conditions caused, in part, by reductions in flowing water over time due to a combination of anthropogenic activities and drought. In all scenarios except for Scenario 2, over the next 50 years, this population becomes functionally extirpated as unhealthy habitat factors contribute to further declines in reproduction, leading to subsequent declines in abundance and occupied stream length over time. Conservation in Scenario 2, would enhance substrate conditions, maintain flows, and improve water quality in the Lower San Saba River; the population would, therefore, be likely to maintain current population factors. DR Table D.14. Projection of Texas fawnsfoot population conditions in the Lower San Saba River currently and in 50 years under four future scenarios. Scenario Texas Fawnsfoot: Lower San Saba River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Current Moderate Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Unhealthy Unhealthy Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Overall Condition Moderate Unhealthy Unhealthy The currently moderately healthy Lower Colorado River population (Table D.15) is expected to remain extant over the next 50 years in all scenarios except Scenario 4. The Lower Colorado River is expected to remain flowing to provide water to downstream senior rights. But, similar to the Lower Brazos River Draft Central Texas Mussels SSA Report E-11 April 2018 population, the Lower Colorado River is vulnerable to reduced flows and associated habitat degradation, because the Texas fawnsfoot occurs in bank habitats that are likely to become exposed to desiccation, predation, and increased water temperatures as river elevations decline while the river still flows in its main channel (i.e., thalweg). In Scenario 2, flows are managed such that the bank habitats are adequately wetted, and releases are managed such that excessive scour is reduced, leading to an overall healthy condition in 50 years. In Scenario 1 and 3, flows are reduced, negatively affecting substrate quality and water quality (through increased sediment load and water temperature) such that reproduction and abundance are negatively affected, leading to overall unhealthy population condition. In Scenario 4, bank habitats are dewatered frequently and scour associated with floods from major storms and dam releases degrade habitat factors to the point that the already low and slow to reproduce population can no longer persist. T Table D.15. Projection of Texas fawnsfoot population conditions in the Lower Colorado River currently and in 50 years under four future scenarios. Overall Condition Current Healthy Moderate Healthy Moderate Scenario 1 Moderate Unhealthy Unhealthy Scenario 2 Healthy Healthy Healthy Scenario 3 Moderate Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. AF Scenario Texas Fawnsfoot: Lower Colorado River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Moderate Moderate Unhealthy Unhealthy Unhealthy Unhealthy Moderate Moderate Healthy DR Moderate The currently unhealthy East Fork of the Trinity River population (Table D.16) is characterized by moderately healthy habitat factors, which are expected to remain moderately healthy over the next 50 years in all scenarios, largely because of the influence of return flows in this highly managed segment. This population occupies a small spatial extent, making it especially vulnerable to a single stochastic event such as a spill or flood. Further, no evidence of reproduction exists for this population. Currently unhealthy low levels of reproduction are expected to lead to unhealthy low abundances and an overall unhealthy population condition in 50 years for Scenario 1 and Scenario 2. In Scenario 3 and Scenario 4, habitat factors decline but remain in the moderately healthy range given interactions between additional climate forcings and water demands, combined with current unhealthy levels of reproduction, are expected to lead to functional extirpation due to very low abundance and with more frequent and prolonged periods minimum flows over the next 50 years. That is, while the habitat factors remain in the moderately healthy category, they still decline somewhat (i.e., flows are more often closer to the managed minimum flow requirement rather than almost always meeting the requirement). This population is small and isolated from the middle and lower Trinity River population, by unsuitable habitat affected primarily be altered hydrology as flows from the Dallas-Fort Worth metro area are too flashy to provide suitable habitat for Texas fawnsfoot. This population has low resilience, but that low resilience can likely be maintained through conservation actions by parties that are currently involved in managing the occupied Draft Central Texas Mussels SSA Report E-12 April 2018 sections of the East Fork of the Trinity River, to the extent that future return flows are adequate for maintaining this population. Table D.16. Projection of Texas fawnsfoot population conditions in the East Fork of the Trinity River currently and in 50 years under four future scenarios. Scenario Texas Fawnsfoot: East Fork Trinity River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Unhealthy Moderate Unhealthy Moderate Moderate Moderate Unhealthy Scenario 1 Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 2 Unhealthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Moderate Moderate Moderate Func. Ext. AF T Current DR The currently unhealthy Trinity River population (Table D.17) is subject to moderately healthy habitat factors as water quality has improved substantially over the past 30 years, as streamflow is subsidized by return flows originating in part from other basins and the fact that a relatively long and unobstructed run of river currently exists. The population factors include unhealthy low levels of reproduction, which leads to unhealthy low abundances in all future scenarios in 50 years. Occupied stream length remains healthy in Scenario 1 and 2 but degrades to moderately healthy as anthropogenic activities and climate forcings combine to further alter the hydrology of the system, largely through excessive scour reducing quality and quantity of flow-protected bank habitats. In all future scenarios, the Trinity River population of Texas fawnsfoot is expected to maintain an unhealthy overall population condition. Table D.17. Projection of Texas fawnsfoot population conditions in the Trinity River currently and in 50 years under four future scenarios. Scenario Texas Fawnsfoot: Trinity River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Moderate Unhealthy Moderate Moderate Moderate Unhealthy Scenario 1 Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 2 Healthy Unhealthy Unhealthy Moderate Moderate Moderate Unhealthy Scenario 3 Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy Scenario 4 Moderate Unhealthy Unhealthy Unhealthy Moderate Moderate Unhealthy In Summary, within 50 years and assuming Scenario 1, three of seven populations become functionally extirpated, three would be in unhealthy condition, and one population would be moderately healthy. Draft Central Texas Mussels SSA Report E-13 April 2018 Assuming Scenario 3 and Scenario 4, four and five populations become functionally extirpated, respectively. D.4 TEXAS PIMPLEBACK Texas pimpleback is currently represented by five populations in the Colorado River basin and by two populations in the Guadalupe River basin. Reproductive output is currently in an unhealthy low condition, in six of the seven populations. T The currently unhealthy Concho River population (Table D.18) is threatened by unhealthy habitat factors, most notably unhealthy low levels of flowing water combined with unhealthy water and substrate quality. The Concho River population is also experiencing unhealthy population condition as evidenced by low occupied stream length, low abundance, and low reproduction, largely as a consequence of unhealthy habitat conditions during the 2011-12 drought. This population is vulnerable to future low water events, and in every scenario, and within 50 years, this population is functionally extirpated due to unhealthy habitat conditions and concomitant low abundance and reproductive failure. Scenario AF Table D.18. Projection of Texas pimpleback population conditions in the Concho River currently and in 50 years under four future scenarios. Texas Pimpleback: Concho River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. DR Current Scenario 2 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. The currently moderately healthy Middle Colorado River and Lower San Saba River population (Table D.19) is similarly threatened by unhealthy habitat conditions, due to a combination of reduced flows, impaired water quality, and substrate degradation. Within 50 years, this population is expected to become functionally extirpated in all scenarios, except for Scenario 2. Scenario 2 establishes positive conservation programs that maintain flows during droughts, which serves to maintain status quo moderately healthy water and substrate quality. However, due to currently unhealthy levels of reproductive output, abundance declines to unhealthy and occupied stream length declines to moderately healthy levels after 50 years, even given these conservation measures. The resiliency of this population is likely tied to the capacity for the lower San Saba River to sustain adequate base flows and thus is sensitive to hydrologic changes associated with anthropogenic actions and climate forcings. Some mussel beds within this population, due to ease of access, are vulnerable to the threat of over-collection and Draft Central Texas Mussels SSA Report E-14 April 2018 vandalism, which negatively affects each of the three population factors. Scenario 2 establishes a monitoring and regulatory framework to lessen the adverse effects of over-collection and vandalism. Table D.19. Projection of Texas pimpleback population conditions in the Middle Colorado and San Saba Rivers currently and in 50 years under four future scenarios. Scenario Texas Pimpleback: Middle Colorado and San Saba Rivers Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Healthy Unhealthy Moderate Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Moderate Unhealthy Unhealthy Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Unhealthy AF T Moderate Moderate DR The currently unhealthy Upper San Saba River population (Table D.20) is similarly dependent on current and future sustainability of spring-fed base flows in the Upper San Saba River. This population is expected to become functionally extirpated within 50 years in all scenarios except for Scenario 2, due to unhealthy habitat factors interacting with existing unhealthy reproduction conditions, combined with threats of reduced spring flows during future droughts (i.e., repeat of 2011). Because of the proximity of this location to the springs, this population is somewhat more resilient than the lower San Saba River, such that if conservation actions are implemented, including flows management during drought, the population may be able to sustain in a moderately healthy condition. In scenarios 1, 3, and 4 flow reductions result in declines in habitat factors to unhealthy conditions. Because of the “losing reach” near Hext, Texas, that serves to separate the upper and lower San Saba River populations, along with differences in substrate, this population is isolated and no longer connected to the lower San Saba River population. Draft Central Texas Mussels SSA Report E-15 April 2018 Table D.20. Projection of Texas pimpleback population conditions in the Upper San Saba River currently and in 50 years under four future scenarios. Scenario Texas Pimpleback: Upper San Saba River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Current Moderate Unhealthy Unhealthy Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Moderate Moderate Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Unhealthy Moderate T Moderate Moderate Overall Condition DR AF The currently unhealthy Llano River population (Table D.21) occupies a very short stream length, which is negatively affected by substrate degradation during periods of low flows. Within 50 years, this population is expected to become functionally extirpated in all scenarios, except for Scenario 2 due to unhealthy habitat factors interacting with existing unhealthy population abundance and reproduction conditions, combined with threats of reduced spring flows during future droughts (i.e., repeat of 2011). Scenario 2 establishes positive conservation programs that maintain flows during droughts, which serves to maintain status quo moderately healthy riffle habitats, improving reproductive output and abundance, lifting the overall population condition to moderately healthy. This population, due to ease of access to the location, is especially vulnerable to the threat of over-collection and vandalism, which negatively affects each of the three population factors. Scenario 2 establishes an adaptive management monitoring and regulatory framework to lessen the adverse effects of over-collection and vandalism. Table D.21. Projection of Texas pimpleback population conditions in the Llano River currently and in 50 years under four future scenarios. Scenario Texas Pimpleback: Llano River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate Current Unhealthy Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Moderate Moderate Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Overall Condition Moderate Unhealthy Moderate The currently moderately healthy Lower Colorado River population (Table D.22) becomes functionally extirpated within 50 years under all scenarios except for Scenario 2, which establishes an adaptive Draft Central Texas Mussels SSA Report E-16 April 2018 framework for monitoring mussel populations and managing flows during critical dry periods. Being a riffle specialist, the Texas pimpleback is especially sensitive to hydrological alterations leading to both extreme drying (dewatering) during low flow events, and to extreme high flow events leading to scouring of substrate and movement of mature individuals to sites that may or may not be appropriate (as evidenced by the August 2017 scouring flood event that substantially degraded the quality of the Altair Riffle in the Lower Colorado River, a formerly robust mussel bed). The frequency and severity of extremely low- and high-flow events are influenced by anthropogenic actions and climate forcings, and interactions between the two. If status quo habitat factors can be maintained, in light of continuing climate change and growing water demands, then it may be possible to maintain moderately healthy overall population condition for Texas pimpleback in the Lower Colorado River. Table D.22. Projection of Texas pimpleback population conditions in the Lower Colorado River currently and in 50 years under four future scenarios. Overall Condition Current Healthy Moderate Unhealthy Moderate Moderate Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Healthy Moderate Moderate Moderate Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. T Scenario Texas Pimpleback: Lower Colorado River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Moderate AF Moderate Moderate Moderate Moderate DR The currently unhealthy Upper Guadalupe River population (Table D.23) currently occupies a long stream length, with moderately healthy water quality and quantity conditions. However, because of unhealthy low abundance and an apparent lack of reproduction, and poor substrate conditions, this population is overall unhealthy and is expected to become functionally extirpated within 50 years, under all scenarios except for Scenario 2. This population is expected to be sensitive to potential changes in groundwater inputs to stream flow and thus is vulnerable to ongoing and future hydrological alterations that reduce flows during critical conditions, resulting in substrate quality impairments. If conservation programs conceived of in Scenario 2 can successfully maintain status quo habitat conditions, then this population is expected to be in an unhealthy overall condition due to declines in abundance and occupied stream length due to apparent reproductive failures. (Note: This population may, in fact, represent a species other than Texas pimpleback.) Draft Central Texas Mussels SSA Report E-17 April 2018 Table D.23. Projection of Texas pimpleback population conditions in the Upper Guadalupe River currently and in 50 years under four future scenarios. Scenario Texas Pimpleback: Upper Guadalupe River Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 1 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 2 Unhealthy Unhealthy Unhealthy Unhealthy Scenario 3 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Scenario 4 Func. Ext. Func. Ext. Func. Ext. Unhealthy Unhealthy Unhealthy Func. Ext. Moderate Moderate Unhealthy T Moderate Moderate DR AF The currently moderately healthy San Marcos River and Lower Guadalupe River population (Table D.24) currently occupies a relatively long stream length, is observed in relatively high abundances, and provides evidence of moderately healthy reproduction. Moderately healthy substrate conditions, flowing water, and water quality contributes to an overall moderately healthy population condition, which is expected to persist for the next 50 years under Scenario 1 and Scenario 2. Significant spring complexes contribute substantially to baseflow during dry periods in this system and are expected to continue to contribute to baseflows for the next 50 years due to conservation measures implemented by the EAHCP partners, bolstering the resiliency of this population. Under Scenario 3 and Scenario 4, the combination of anthropogenic actions with climate forcings negatively affects the hydrologic status of this section of the river and reduces the habitat factors to unhealthy condition due to lowered stream flows. Unhealthy habitat conditions are expected to lead to reductions in reproduction and abundance conditions, leading to an overall unhealthy population condition within 50 years, under Scenario 3 and Scenario 4. (Note: This population may, in fact, represent a species other than Texas pimpleback.) Table D.24. Projection of Texas pimpleback population conditions in the San Marcos and Lower Guadalupe Rivers currently and in 50 years under four future scenarios. Scenario Texas Pimpleback: San Marcos and Lower Guadalupe Rivers Population Factors Habitat Factors Stream Flowing Water Length Abundance Reproduction Substrate Water Quality Overall Condition Current Healthy Healthy Moderate Moderate Moderate Moderate Moderate Scenario 1 Healthy Moderate Moderate Moderate Moderate Moderate Moderate Scenario 2 Healthy Moderate Moderate Moderate Moderate Moderate Moderate Scenario 3 Healthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Scenario 4 Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Unhealthy Draft Central Texas Mussels SSA Report E-18 April 2018 DR AF T In Summary, within 50 years and assuming Scenario 1, six of seven populations would be functionally extirpated, leaving only the San Marcos and Lower Guadalupe Rivers population extant in a moderately healthy condition. Assuming Scenario 3 and Scenario 4, the sole surviving population would be in an unhealthy overall condition within 50 years. Assuming Scenario 2, one population would be functionally extirpated, two would be unhealthy, and four would be moderately healthy in 50 years. Draft Central Texas Mussels SSA Report E-19 April 2018 APPENDIX E ‐ GLOSSARY OF TERMS USED IN THIS DOCUMENT Bradytictia - Long-term brooders; these species brood glochidia over the winter instead of releasing them immediately. Clade - A group of organisms believed to have evolved from a common ancestor. Congener - Organisms within the same genus. Conglutinates - Cohesive or enveloped masses of eggs or glochidia, formed as molds in the female demibranchs. Curtail or cutback (water) – to reduce the amount of water supply being provided. Desiccation - Extreme drying. T Demibranch- The V-shaped structure of gills common to species in the Class Bivalvia. AF Entrainment - The entrapment of one substance by another substance; in this instance the entrapment of mussels by sediment or other immovable barriers during high-flow events (flood and scour). Firm Water – Water that can be supplied on a consistent (or “firm”) basis from lakes Buchanan and Travis through a repeat of the worst drought in recorded history for the lower Colorado River basin, which is the drought of the 1940s and 50s, while honoring all downstream water rights. This drought is known as the Drought of Record. Flow refuges - Hydraulic shelters, where shear stress is relatively low and where sediments are relatively stable during large floods. Glochidia - Parasitic larvae of freshwater mussels. DR Gravid - Condition of having glochidia within the gills of a female mussel. Haplotype - A group of genes within an organism that was inherited together from a single parent. Hypolimnion - The lower layer of water in a stratified lake, typically cooler than the water above and relatively stagnant. Incurrent siphon - The tubular structure used to draw water into the body of the mussel. Interruptible Stored Water – Water from lakes Buchanan and Travis that must be cut back or cut off during drought or times of shortage to ensure that LCRA can meet Firm Water customer Demands. Interstitial spaces - Small openings in an otherwise closed matrix of substrate. Lentic - Standing water habitats typical of ponds, lakes, and reservoirs. Littoral - Describing bank habitats. Lotic - Flowing water habitats typical of springs, streams, and rivers. Malacologist - Scientist that studies mollusks, including freshwater mussels. Marsupial chamber - Specialized areas of the gills in which fertilized eggs are held until maturation. Draft Central Texas Mussels SSA Report E-1 April 2018 Molluscivorous - Mollusk-eating. Mussel bed - An aggregation of mussels, of one or more species, at a mesohabitat scale. Phylogenetic - Relating to the evolutionary development and diversification of a species. Positive rheotaxis - Behavior in which an organism orients and swims against oncoming flows. Priority call - A senior water right holder (one who has held that right the longest) can make a call for water over one with a junior right (one held for a shorter time). Recruitment - Survival of juveniles to join the adult, reproducing population. Redundancy -The ability of a species to withstand catastrophic events. T Representation - The ability of a species to adapt to changing environmental conditions over time. Resiliency - The ability of populations to withstand stochastic disturbance. Riffle - A rocky or shallow part of a river or stream with rough water. AF Run-of-river flows – The flow in the river that is available under law at a given point on the river at a given point in time to honor a water right with a given priority date. Rights to use run-ofriver flows for beneficial uses, rights to store inflows in reservoirs, and pass-through of inflows and releases from reservoirs, are regulated by the TCEQ. Sexual Dimorphism - Differences in form between male and female individuals of the same species. Tachytictia - Short-term brooding; tachytictic mussel species spawn in the spring, embryos and larvae are developed and released as glochidia that same season. DR The 3Rs - The conservation biology principles of representation, resiliency, and redundancy used to evaluate the current and future conditions a species Unionids - Freshwater mussels of the family Unionidae. Viability - The ability of the Central Texas mussels to sustain populations in natural river systems over time. Watermaster - In some parts of the state, watermasters allocate water between users and ensure compliance with water rights. Draft Central Texas Mussels SSA Report E-2 April 2018