Malacological Review, 2017, 45: 1-163 HISTORICAL AND CURRENT EXAMINATION OF FRESHWATER MUSSELS (BIVALVIA: MARGARITIFERIDAE: UNIONIDAE) IN THE DUCK RIVER BASIN TENNESSEE, U.S.A. Steven A. Ahlstedt1, Jeffrey R. Powell2, Robert S. Butler3, Mark T. Fagg4, Don W. Hubbs5, Sabrina F. Novak6, Sally R. Palmer7, and Paul D. Johnson8 CONTENTS ABSTRACT……………………………………………………………………………………2 INTRODUCTION………………………………………………………………………………2 Historical accounts of humans and mussels …………………………………………………3 Historical background for current study………………………………………………………4 Previous mollusk studies of the Duck River drainage………………………………………5 STUDY AREA……………………………………………………………………………………6 METHODS………………………………………………………………………………………8 River discharge evaluation……………………………………………………………………8 Qualitative mussel sampling…………………………………………………………………8 Quantitative sampling of freshwater mussels………………………………………………16 Juvenile mussel distribution…………………………………………………………………17 RESULTS………………………………………………………………………………………17 River discharge evaluation…………………………………………………………………17 Qualitative mussel sampling…………………………………………………………………19 Species accounts……………………………………………………………………………22 Quantitative mussel sampling………………………………………………………………91 Juvenile mussel distribution…………………………………………………………………91 DISCUSSION…………………………………………………………………………………91 River discharge evaluation…………………………………………………………………91 Qualitative mussel sampling…………………………………………………………………97 Duck River tributaries………………………………………………………………………98 Quantitative mussel sampling………………………………………………………………99 Summary……………………………………………………………………………………100 ACKNOWLEDGEMENTS…………………………………………………………………101 REFERENCES………………………………………………………………………………101 APPENDICES…………………………………………………………………………………104 Appendix 1 – Results of qualitative mussel sampling at 112 sites…………………………104 Appendix 2 – Results of quantitative mussel sampling……………………………………116 Appendix 3 – Historical freshwater mussel database………………………………………122 Appendix 4 – Species summary of the Duck River Basin…………………………………163 1United States Geological Survey, 1820 Midpark Drive, Knoxville, Tennessee 37921 U.S.A; Current Address, P.O. Box 460 Norris, Tennessee 37828 U.S.A. 2United States Geological Survey, 640 Grassmere Park, Nashville, Tennessee 37211 U.S.A.; Current Address, United States Fish and Wildlife Service, P.O. Drawer 1190, Daphne, Alabama 36526 U.S.A. 3United States Fish and Wildlife Service, 160 Zillicoa Avenue, Street, Asheville, North Carolina 28801 U.S.A. 4Tennessee Wildlife Resources Agency, 3030 Wildlife Way, Morristown, Tennessee 37814 U.S.A. 5Tennessee Wildlife Resources Agency, Fisheries Management, P.O. 40747, Nashville, Tennessee 37204 U.S.A. 6Tennessee Aquarium Research Institute, 5385 Red Clay Road, Cohutta, Georgia 30710, U.S.A.; Current Address, Hamilton County Health Department, 921 E. 3rd Street, Chattanooga, TN 37403 U.S.A. 7The Nature Conservancy, Duck River Project, 106A Riverside Drive, Columbia, Tennessee 38401 U.S.A. 8Alabama Aquatic Biodiversity Center, 2200 Highway 175, Marion, Alabama 36756 U.S.A. (1) 2 Ahlstedt et al. ABSTRACT The Duck River basin located in south-central Tennessee has long been established as an area of high freshwater mussel diversity. The Duck River is 442 km long with a large reservoir, Normandy Dam oper- ated by the Tennessee Valley Authority (TVA) placed at river km 420 controlling discharge throughout the remaining river (≈ 95% total length). This inventory effort examined 112 sites throughout the Duck River basin for freshwater mussels. Additionally, historical species records were assembled directly from natural history museum records across North America to examine changes in species richness and distribution. For freshwater mussels, 75 species historically occurred in the basin, and 53 are currently extant, including three federally listed species (Epioblasma sp. cf. capsaeformis, Lemiox rimosus, and Quadrula intermedia). Mussel densities examined either as Catch Per Unit Effort (CPUE) or direct quadrat sampling indicated significant increases from 1979, 1988, and 2001-2002. In qualitative sampling, mussel species richness more than tripled and mussel numbers increased 11 fold at 17 sites common to mussel studies in 1979, 1988, and 2002. Mean mussel densities at three locations increased between two and 11 fold and species richness 3 and 6.5 fold in quadrat sampling. As a general trend, mussel species richness increased down- river, with a mean diversity of 17.6 species per site in the lower drainage, although the highest diversity sites were associated with mill dams. Mussel species richness was not significantly different (p = 0.76) across 12 sites sampled in 1922, 1965, and 2002. Populations of federally listed species have increased their range substantially and numbers encountered were significantly greater in both qualitative and quantitative sampling. In direct contrast to the main-stem river, mussel species richness has declined dramatically in tributary systems over the last 20 years. Mussel recovery in the Duck River is attributable in part to im- provements in point source elimination, and land acquisition from the now defunct TVA, Columbia Dam Project. However, improvements in dissolved oxygen concentrations and flow release schedules from Normandy Dam initiated by TVA’s - Reservoir Release Improvements (RRI) program in 1991 are likely the most critical development in mussel recovery. From 1991–2001 mean annual discharges improved 23 and 15% during critical spring and summer recruitment periods in comparison to discharge levels 10 years previous. Increased channel volume during critical recruitment periods improves conditions on channel margins where mussel recruitment is most critical. The apparent long-term stability for mollusk species richness and abundance, along with an enormously diverse riverine fauna (total biodiversity exceeds 650 species) make the Duck River an outstanding national resource. INTRODUCTION In terms of biodiversity, the Duck River is one if not the most biologically diverse rivers in North America. A total of 147 species of fish, 54 freshwater mussel species, and 22 freshwater snail species occur here (Appendix 4). The mussel fauna of the Duck River has a long history of abuse and neglect that was not uncommon for many streams during the settlement and industrialization of our nation. Since the passage of the Clean Water and Endangered Species Acts by Congress in 1972 and 1973, respectively, recent awareness of this unique faunal group have shown precipitous declines and extinctions for mussels and snails, by far more than any other faunal group in the country. Species richness in terms of freshwater mollusks (mussels, fingernail clams, aquatic snails) in the United States consists of more than 940 species (297 mussels, 38 fingernail clams, 655 snails). Of these, 269 mussels, 53 fingernail clams, and 313 snails occur in the southeastern United States. When species richness is assessed from a regional perspective, it is readily apparent that the “rain forest” of mollusk diversity is in the southeastern United States. A recent status review of the mussel fauna in the entire United States revealed significant nationwide declines (Williams et al., 1993). In the southeastern states, about 35 species of mussels have been lost (unpublished recent estimate) and between 34 percent and 71 percent of all mussels are imperiled, defined here to include species endangered, threatened, or of special concern (Neves et al., 1997). Archaeological excavations of aboriginal shell mounds Duck River mussels 3 are historical proof of extensive mussel colonization in our rivers. Snails have faired little better with nearly 60 species lost and between 5 percent and nearly 49 percent remaining species considered endangered, threatened, or of special concern for some southeastern states (Johnson et al., 2013). However, the mollusk fauna that exists today in streams like the Duck River is but a small fraction of a fragmented and disjunct fauna that nationwide has managed to survive extensive human perturbations. Efforts to save molluscan resources will take closely coordinated partnerships and a long-term commitment by governmental and non-governmental conservation organizations in its preservation. Current study objectives of this examination of Duck River basin freshwater mussels were diverse. The first objective was to complete a comprehensive qualitative mussel survey of the Duck River basin focusing on the main stem river and selected tributaries below Normandy Dam. Not only would this generate a current species list, but an expanded study area would allow for a better assessment than other recent investigations (Ahlstedt, 1981, 1991; Jenkin- son, 1988; Schilling and Williams, 2002). The second objective was to complete quantitative surveys at specific localities in the river where previous examinations were completed in 1979 and 1988. This would allow us to quantify changes in mussel density and species richness over time. The third objective was to assemble an historical database for detailed examination of changes in species occurrences and distribution since the 1880’s. This would be accomplished through the direct examination of museum collections and the assembly of records into a single historical database. Additional recent survey records were also compiled into this database (Hubbs, 1999; Schilling and Williams, 2002). These additional records were invaluable when crafting accounts of each species. The fourth objective was to compile information related to changes in river management that may compromise or improve mussel populations.