Impacts of habitat loss by reservoir inundation on occurrence, abundance, and genetic diversity of an imperiled, river-adapted, benthic-specialist fish, Etheostoma lemniscatum (Tuxedo Darter)

Abstract Dams homogenize habitat and alter natural depth and flow regimes of lotic habitats, leading to extirpation of many stream-adapted fishes such as darters (Percidae). The Tuxedo Darter, Etheostoma lemniscatum , is a habitat-specialist of shallow, flowing pools with cobble substrate in the Big South Fork Cumberland River. One threat to this species is Wolf Creek Dam on the Cumberland River that creates Lake Cumberland, which during summer pool, inundates the lower 72 river kilometers (rkms) of the Big South Fork. A six-year period of lower reservoir elevations for dam repairs allowed a 9 rkm reach to return to riverine habitat and E. lemniscatum to colonize this reach. Once dam repairs were complete, the lower 72 rkms were again regularly inundated by Lake Cumberland. To determine the impact of post-dam repair inundation on E. lemniscatum , we compared occurrence, abundance, and genetic diversity metrics estimated from samples from 2015 and from several years post-inundation in 2019 and 2020 from 11 sites spanning the species’ range. Declines in occurrence and abundance were detected within the re-inundated reach. We observed low genetic diversity for the species for both sample periods, but no significant changes in genetic diversity between years. A trend towards lower allelic richness and an increase in the proportion of private alleles was observed in the 2019/2020 samples. Coupled with local extirpation and declines in abundance, these trends may be early warning signs of future declines in genetic diversity. We suggest future genetic monitoring to identify any time delayed responses to inundation not detected herein.