The Freshwater Mussels (Bivalvia: Unionidae) of the Harpeth River Drainage and the Upper and Middle Duck River Tributaries, Tennessee

The Cumberland and Tennessee River drainages harbor high diversity and endemism of freshwater mussels. The faunas of the Harpeth River drainage and Duck River tributaries have been disproportionally understudied relative to other Cumberlandian streams. Forty-two sites on 23 tributaries in the Harpeth River drainage and a 21-kilometer reach of the main channel were assessed qualitatively for freshwater mussels. Relic shells of four species were observed in eight sites on four of the tributaries. Twenty species were observed in the main channel including the discovery of a new Harpeth River drainage record: Simsponaias ambigua. Catch per unit effort (CPUE) ranged from 0.0 to 32.0 mussels/h. Lampsilis fasciola and Potamilus alatus were the most abundant species. Mussel populations were fragmented and all species exhibited primarily large size-classes. Eighty-three sites on 37 tributaries in the upper and middle Duck River drainage were sampled qualitatively. Nineteen species were observed and 12 were collected live or fresh dead, and CPUE ranged from 0.0 to 58.0 mussels/h. Villosa vanuxemensis and Villosa taeniata were the most abundant and widespread species observed. Live mussels were found in only five tributaries, although mussels historically occurred in 17 of the sampled streams. Length frequency analysis indicated recent recruitment for four species in Big Rock Creek. Results of canonical correspondence analysis for both drainages revealed no association between environmental variables and mussel community structure (live and fresh dead individuals combined), likely a result of low densities. Two sites on Big Rock Creek in the Duck River drainage were sampled quantitatively using 0.25-m² quadrats. Densities were 0.33 and 1.27 mussels/0.25m² and species richness ranged from four to five. Quantitative sampling indicated that qualitative timed searches may be sufficient for detecting recruitment in small streams. Anthropogenic alteration has resulted in extensive loss of freshwater mussel habitat, leading to local extirpations and a reduction of diversity and abundance in both watersheds.