Species Status Assessment Report for the Ashy Darter (Etheostoma cinereum) Version 1.0 Photo Credit: Bernard Kuhajda, Tennessee Aquarium Conservation Institute March 2018 Contents CHAPTER 1. INTRODUCTION ................................................................................................... 1 CHAPTER 2. SPECIES NEEDS AND DISTRIBUTION ............................................................. 3 Taxonomy ............................................................................................................................... 3 Genetic Diversity .................................................................................................................... 3 Morphological Description ..................................................................................................... 3 Habitat ..................................................................................................................................... 5 Population Needs ........................................................................................................................ 8 Species Needs ............................................................................................................................. 8 Range and Distribution ............................................................................................................. 10 Historical Range.................................................................................................................... 10 CHAPTER 3. FACTORS INFLUENCING VIABILITY ............................................................ 13 Impoundments........................................................................................................................... 13 Physical Habitat Disturbance .................................................................................................... 14 Contaminants ............................................................................................................................ 15 Sedimentation ........................................................................................................................... 15 Reduced Range/Isolation .......................................................................................................... 16 Climate Change ......................................................................................................................... 16 Conservation Actions ................................................................................................................ 17 CHAPTER 4. CURRENT MANAGEMENT UNIT CONDITION ............................................. 18 Population Elements ................................................................................................................. 18 Habitat Elements ....................................................................................................................... 19 Current Population Status ......................................................................................................... 20 Upper Tennessee Management Unit ..................................................................................... 21 Elk River Management Unit ................................................................................................. 26 Duck River Management Unit .............................................................................................. 27 Current Species Level Status .................................................................................................... 29 Representation....................................................................................................................... 29 Redundancy........................................................................................................................... 30 CHAPTER 5: FUTURE SCENARIOS AND SPECIES VIABILITY ......................................... 31 Scenarios ................................................................................................................................... 32 Scenario F ............................................................................................................................. 32 Scenario W ............................................................................................................................ 35 Scenario S ............................................................................................................................. 38 i Status Summary ........................................................................................................................ 40 Future viability ...................................................................................................................... 40 Uncertainty ............................................................................................................................ 41 Overall Summary ...................................................................................................................... 41 References ................................................................................................................................. 43 Appendices ................................................................................................................................ 50 ii CHAPTER 1. INTRODUCTION The ashy darter (Etheostoma cinereum) is a fish in the family Percidae (Shepard and Burr 1984, p. 696) endemic (restricted to a locality or region) to the Tennessee River system. The ashy darter was designated a Category 2 Candidate species in 1994 (59 FR 58997), and remained such until that list was discontinued in 1996 (61 FR 64481). The ashy darter was petitioned to be listed under the Endangered Species Act of 1973, as amended (Act), as part of the Center for Biological Diversity’s 2010 Petition to List 404 Aquatic, Riparian and Wetland Species from the Southeastern United States (CBD 2010, p. 428-431). In this report, we use the Species Status Assessment (SSA) framework (Smith et al. 2018, entire) to conduct 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. The intent is for the SSA Report to be updated as new information becomes available and to support all functions of the Endangered Species Program from Candidate Assessment to Listing, to Consultations and Recovery. As such, the SSA Report will be a living document upon which other decision documents would be based if the species warrants listing under the Act, including listing rules, recovery plans, and 5-year reviews. This SSA Report for the ashy darter provides the biological support for the decision on whether or not to propose to list the species as threatened or endangered and, if so, where to propose designating critical habitat. Importantly, the SSA Report is not the decision by the Service on whether to propose the ashy darter for listing as a threatened or endangered species under the Act. Instead, this SSA Report provides a review of the available information strictly related to the biological status of the ashy darter. The listing decision will be made by the Service after reviewing this document and all relevant laws, regulations, and policies, and the results of a proposed decision will be announced in the Federal Register, with appropriate opportunities for public input. For the purpose of this assessment, we generally define viability as the ability of the ashy darter to sustain natural populations in the Tennessee River system over time. Using the SSA framework (Figure 1.1), we consider what the species needs to maintain viability by characterizing the status of the species in terms of its resiliency, redundancy, and representation (Shaffer and Stein, 2000, entire; Wolf et al. 2015, entire). ● Resiliency describes the ability of populations to withstand stochastic events (arising from random factors). We can measure resiliency based on metrics of population health; for example, birth versus death rates and population size. Highly resilient populations are better able to withstand disturbances such as random fluctuations in birth 1 rates (demographic stochasticity), variations in rainfall (environmental stochasticity), or the effects of anthropogenic activities. ● Representation describes the ability of a species to adapt to changing environmental conditions. 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 species- specific genetic and ecological diversity information, we evaluate representation based on the extent and variability of habitat Figure 1.1 Species Status Assessment characteristics across the geographical range Framework and other factors as appropriate. ● Redundancy describes the ability of a species to withstand catastrophic events. Measured by the number of populations, their resilience, 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). To evaluate the biological status of the ashy