Candy Darter Species Status Assessment (SSA) Report
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Species Status Assessment (SSA) Report for the Candy Darter (Etheostoma osburni) Version 1.4 Candy darter (Photo credit: Dr. Stuart Welsh, U.S. Geological Survey) September 2017 U.S. Fish and Wildlife Service Northeast Region Hadley, MA This document was prepared by Keith Hastie (U.S. Fish and Wildlife Service (USFWS)- Northeast Regional Office), Barbara Douglas (USFWS-West Virginia Field Office), Jordan Richard (USFWS-Southwestern Virginia Field Office), Krishna Gifford (USFWS-Northeast Regional Office), Heather Bell (USFWS-Headquarters (HQ)), Andy DeVolder (USFWS-HQ), and Jonathan JaKa (USFWS-HQ). We greatly appreciate the assistance of Dan Cincotta (West Virginia Division of Natural Resources (WVDNR)), Isaac Gibson (WVDNR and West Virginia University), Mike Pinder (Virginia Department of Game and Inland Fisheries), Paul Angermeier (U.S. Geological Survey (USGS)), Stuart Welsh (USGS), Andy Dolloff (U.S. Forest Service (USFS)), Dawn Kirk (USFS), Chad Landress (USFS), Jesse Purvis (National Park Service), Katie McBaine (Virginia Polytechnic Institute (VPI)), and Corey Dunn (University of Missouri), who provided helpful information and review of the draft document. We also thank Meredith Bartron (USFWS-Northeast Fishery Center), Emmanuel Frimpong (VPI), Carla Hurt (Tennessee Technical University), and James Roberts (Georgia Southern University), who conducted peer review and provided helpful comments. Suggested reference: U.S. Fish and Wildlife Service. 2017. Species Status Assessment Report for the Candy Darter (Etheostoma osburni), Version 1.4. September 2017. Hadley, MA. Contents EXECUTIVE SUMMARY ............................................................................................................ 1 Background ................................................................................................................................. 7 Analytical Framework ................................................................................................................ 7 CHAPTER 2 – SPECIES INFORMATION ................................................................................. 10 Taxonomy and Genetics ........................................................................................................... 10 Species Description ................................................................................................................... 13 Life History ............................................................................................................................... 14 Physical Setting ......................................................................................................................... 17 Habitat Needs ............................................................................................................................ 21 Historical Range and Distribution ............................................................................................ 25 Current Range and Distribution ................................................................................................ 27 CHAPTER 3 – CURRENT CONDITIONS ................................................................................. 29 Methodology ............................................................................................................................. 29 Analytical Units ........................................................................................................................ 29 Factors Influencing Current Condition ..................................................................................... 31 Hybridization ........................................................................................................................ 31 Sedimentation ....................................................................................................................... 37 Water Temperature ............................................................................................................... 38 Water Chemistry ................................................................................................................... 39 Water Flow............................................................................................................................ 40 Habitat Fragmentation .......................................................................................................... 41 Nonnative Competition and Predation .................................................................................. 42 Candy Darter Current Condition ............................................................................................... 43 Model .................................................................................................................................... 43 Current Condition—3Rs ....................................................................................................... 43 Summary ............................................................................................................................... 50 CHAPTER 4—SPECIES VIABILITY......................................................................................... 51 Future Scenarios........................................................................................................................ 51 Habitat Change (Scenarios 1 and 2)...................................................................................... 51 Variegate Darter Expansion (Scenario 3) ............................................................................. 52 Variegate Darter Expansion with Positive Habitat Change (Scenario 4) ............................. 54 Variegate Darter Expansion with Negative Habitat Change (Scenario 5) ............................ 54 Results ....................................................................................................................................... 54 Scenario 1 (positive habitat changes) ................................................................................... 54 Scenario 2 (negative habitat change) .................................................................................... 57 Scenario 3 (variegate darter expansion) ................................................................................ 59 Scenario 4 (variegate darter expansion with the positive habitat change) ............................ 62 Scenario 5 (variegate darter expansion with negative habitat change): ................................ 64 Summary ................................................................................................................................... 66 REFERENCES CITED ................................................................................................................. 67 APPENDIX A ................................................................................................................................. 1 APPENDIX B ................................................................................................................................. 1 Model .......................................................................................................................................... 1 Metrics .................................................................................................................................... 1 Metric Scoring ........................................................................................................................ 3 Condition Scoring ................................................................................................................... 5 Results ......................................................................................................................................... 6 EXECUTIVE SUMMARY This report summarizes the results of a species status assessment (SSA) conducted for the candy darter (Etheostoma osburni), which includes relevant information about the species’ life history characteristics and how those characteristics are effected by stressors and conservation measures to those address stressors. This report is intended to provide the biological support for the decision on whether or not to propose to list the species as threatened or endangered under the Endangered Species Act of 1973, as amended (Act). The process and this SSA report do not represent a decision by the U.S. Fish and Wildlife Service (Service) whether or not to list a species under the Act. Instead, this SSA report provides a review of the best available information strictly related to the biological status of the candy darter. Background The candy darter is a small, freshwater fish endemic to 2nd order and larger streams and rivers within portions of the upper Kanawha River basin, which is synonymous with the Gauley and greater New River watersheds in Virginia and West Virginia. The species is considered by both Virginia and West Virginia in their State Wildlife Action Plans to be a species of greatest conservation need. The species is described as a habitat specialist, being most often associated with faster flowing stream segments with coarse bottom substrate (e.g., gravel, cobble, rocks, and boulders), that provides shelter for individual darters. Candy darters are intolerant of excessive sedimentation and stream bottom embeddedness (the degree to which gravel, cobble, rocks, and boulders are surrounded by, or covered with, fine sediment particles). The available candy darter occurrence data, all of which were collected after the aquatic habitat in the