Species Status Assessment Report Holiday Darter

Species Status Assessment Report for the Holiday Darter (Etheostma brevirostrum) Version 1.0 Photo from Fishes of Alabama and the Mobile Basin (Mettee et al. 1996, p. 595) July 2017 U.S. Fish and Wildlife Service Region 4 Atlanta, GA Species Status Assessment Report for Holiday Darter (Etheostoma brevirostrum) Prepared by the U.S. Fish and Wildlife Service EXECUTIVE SUMMARY This species status assessment (SSA) reports the results of the comprehensive status review for the holiday darter (Etheostoma brevirostrum), documenting the species’ historical condition and providing estimates of current and future condition under a range of different scenarios. The holiday darter is small fish native to the upper Coosa River basin in Georgia and Tennessee that occurs in small rivers with good water quality. The SSA process can be categorized into three sequential stages. During the first stage, we consider the holiday darter’s life history and use the conservation biology principles of resiliency, redundancy, and representation (together, the 3Rs) to better understand the “needs” of populations and the species to maintain viability. The next stage involved an assessment of the historical and current condition of the species’ demographics and habitat characteristics. The final stage of the SSA involved making predictions about future viability while considering the species’ responses to anthropogenic and environmental influences that are likely to occur within its range. This process used the best available information to characterize viability as the ability of a species to sustain populations in the wild over time. To evaluate the current and future viability of the holiday darter, we assessed a plausible range of conditions that affect its habitats to allow us to forecast the species’ resiliency, representation, and redundancy. For the purposes of this assessment, populations were delineated using U.S. Geological Survey 10 digit Hydrologic Unit Codes (HUC10s) that are occupied by the species. Resiliency, assessed at the population level, describes the ability of a population to withstand stochastic events. A species needs multiple resilient populations distributed across its range to persist into the future and avoid extinction. A number of factors, including (but not limited to) water quality, water quantity, habitat connectivity, and instream substrate, may influence whether holiday darter populations will occupy available habitat. As we considered the future viability of the species, more populations with high resiliency distributed across the known range of the species can be associated with higher species viability. As a species, the holiday darter has limited resiliency, with the majority of populations considered to be in low resiliency. 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). Redundancy for the holiday darter is characterized by having multiple, resilient and representative populations distributed throughout its range. Furthermore, these populations 2 should maintain natural levels of connectivity between them. Connectivity allows for immigration and emigration between populations and increases the likelihood of recolonization should a population become extirpated. 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 characteristics across the geographical range. The analysis of species’ current condition revealed that the extent of occupied habitat has declined, with most populations currently occupying 20-80% of the historically occupied ranges. All historically known populations remain extant; however, there is little connectivity between them and abundances are qualitatively low. To assess the future condition of the holiday darter, a variety of stressors from urbanization, agriculture, and climate were considered. Populations with low resiliency are considered to be more vulnerable to extirpation, which, in turn would decrease species’ level representation and redundancy. To help address uncertainty associated with the degree and extent of potential future stressors, the 3Rs were assessed using three plausible future scenarios. These scenarios were based, in part, on the results of urbanization and climate models. An important assumption of the predictive analysis was that future population resiliency is largely dependent on water quality, water flow, and structural habitat conditions. Our assessment predicted that all currently extant holiday darter populations would experience negative changes to these important habitat requisites in the future under the most likely scenario, Status Quo. Given scenario 1, the “Status Quo” option, loss of resiliency, representation, and redundancy is expected. Under this secenario, we predicted that three populations would likely be extirpated and the remaining populations would have low resiliency. The extirpation of three populations would reduce redundancy by 43%. Representation would be reduced due to the loss of the only known population in the Coosawattee River basin and range contraction out of Piedmont and Ridge and Valley physiographic provinces. Given scenario 2, the “Best Case” option, we predicted slight improvements to resiliency from the current conditions in one populations although no populations would exhibit “high” resiliency. Two would exhibit “moderate” resiliency, three would exhibit “low” resiliency, and the remaining two populations are expected to become extirpated. Redundancy and representation would decline from current conditions. 3 Given scenario 3, the “Worst Case” option, loss of resiliency, representation, and redundancy is expected. Under this scenario, we predicted that four populations would likely be extirpated and those that remain would have low resiliency. Redundancy would be reduced overall by 57% in. Representation would be reduced due to the loss of the only known populations in the Coosawattee River basin and Alabama as well as range contraction out of Piedmont and Ridge and Valley physiographic provinces. Table E1. Current estimated resiliency and predicted future resiliency of populations under multiple scenarios Population Current Status Quo Best Case Worst Case Conasauga River Low Low Moderate Low Talking Rock Likely Likely Likely Low Creek Extirpated Extirpated Extirpated Mountaintown Likely Likely Low Low Creek Extirpated Extirpated Likely Likely Likely Ellijay River Low Extirpated Extirpated Extirpated Amicalola Creek Moderate Low Moderate Low Etowah River Low Low Low Low Likely Shoal Creek Low Low Low Extirpated Overall Summary Currently, the holiday darter continues to occupy all streams where it was historically known to occur. Based on collection records from the last 10 years, all populations occur over shorter overall stream lengths than historical records, indicating range reduction in these seven populations. No population of holiday darter currently exhibits high resiliency due to the reduction in extent of occupied habitat, low abundance of individuals per population, a simple linear spatial arrangement of records, as well as stressors affecting habitat and water quality. Similarly, representation and redundancy is currently low for this species because multiple resilient populations are lacking, connectivity is limited among populations, and this species is increasingly becoming isolated to the upstream limits of its range in the Blue Ridge physiographic province. Our future scenarios assessment considered the current viability of the species to project likely future viability given plausible scenarios of urban development and climate change. Under no scenario did the species persist in all known populations. Two populations are likely to become extirpated under all scenarios. Under the Status Quo Scenario, a third population is expected to become extirpated and under the Worst Case Scenario, a total of four populations are expected to become extirpated. Resiliency, representation, and redundancy declined in all scenarios due to 4 further range contractions and increased likelihoods for extreme climatic events to impact populations. 5 Table of Contents EXECUTIVE SUMMARY……………………………………………………………………….2 CHAPTER 1 – INTRODUCTION………………………………………………………………..8 CHAPTER 2 – SPECIES BIOLOGY AND INDIVIDIUAL NEEDS…………………………..10 Taxonomic History and Uncertainty……………………………………………………..10 Physical Description…………………………………………………………...………...10 Range and Distribution…………………………………………………………………..11 Biology, Life history, Ecology……………………………………………………………11 CHAPTER 3 – POPULATION AND SPECIES NEEDS……………………………………….14 Holiday Darter Resiliency………...……………………………………………………..14 Holiday Darter Representation…………………………………………………………..16 Holiday Darter Redundancy……………………………………………………………..17

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