Distribution, Abundance, and Biomass of Freshwater Mussels (Bivalvia: Unionidae) in Lake St. Clair

A mussel population survey was conducted in Lake St. Clair with divers using SCUBA to sample at 29 stations throughout the lake. Mean abundance was 2 m-2 and mean biomass was 4.4 g dry wt m-2. Of the 18 species collected, Lampsilis radiata siliquoidea was by far the most abundant, accounting for 45% of all individuals. The age-frequency distribution of L. r. siliquoidea was dominated by individuals between 9 and 12 years old. In contrast, the second most abundant species, Leptodea fragilis, showed yearly variation in recruitment with no apparent trends in year class strength. Annual production of L. r. siliquoidea was 0.20 g m-2 y-1 and the turnover ratio was 0.13. The diversity and composition of mussels in Lake St. Clair appear little changed since the turn of the century, but there are indications that population numbers may be declining in the future