An evaluation of change in the Unionidae in the lower Rocky River from 15 years ago

Ohio Journal of Sciences (abstr.) 118: A28 tributaries of Lake Erie sufficiently large to possess a diverse assemblage of freshwater mussels in the family Unionidae. The regional development of natural conservation efforts to improve water quality was hypothesized to improve the mussel assemblage. The present study sought to determine changes in freshwater bivalve populations since original surveys in the northern region of the river conducted in 2001. Visual and physical touch survey methods were incorporated to locate mussels, all conducted when water levels were low and clear. Water quality was assessed from the records of the Ohio Environmental Protection Agency. Time spent at each survey site ranged from approximately an hour and a half to almost 3 hours, and depended on the extent of its geographic structure, variation in habitat, and presence of live mussels. Live mussels (n = 69) were collected along with empty shells (n = 58), most of which were found in 2 distinct but separate locations. The total assemblage consisted of 8 species in comparison to the 9 that were seen in the same area in 2001, but large shifts in relative abundance occurred. Leptodea fragilis populations decreased precipitously. Populations of Lasmigona costata and L. complanata may be increasing, and the presence of young individuals suggested recruitment, but only of these two 2 species. Mostly older specimens of other species were found, which suggests overall a decrease despite improvements in water quality that has been taking place throughout the Lake Erie watershed.