Davis, M. and R. Hart. 1995. Mussel habitat in the Richmond Island/Lock and Dam 6 tailwater area of Pool 7, Mississippi River, and its importance for recovery of the federally endangered mussel, Lampsilis higginsi. Final report submitted by the Minnesota Department of Natural Resources. 34 pp.
During September and October, 1995, a freshwater mussel survey was conducted in the Mississippi River within navigation pool 7 near Richmond Island at RM 714.2-712. Mussels were collected from thirty 0.25 m2 quadrats at each of four quantitative sampling sites. Divers also collected mussels at eight qualitative sampling sites. Two thousand one hundred sixteen mussels representing twenty-two species of unionids were collected using a combination of quantitative and qualitative sampling methods. Mussel densities ranged from 25-53/m2. Amblema plicata and Obliquaria reflexa were the most abundant species. Mussels were found most often in sand substrates exposed to moderate current velocities. One live adult male and one live adult female Lampsilis higginsi were collected using qualitative methods. These individuals were found downstream of a wingdam in shifting sand substrate and high current velocities. Two recently consumed Lampsilis higginsi were collected from a muskrat midden pile. These individuals were females aged 5 and 7 years. Density of Dreissena polymorpha found at quantitative sites ranged from 5-84/m2. Dreissena polymorpha were attached to 9-44% of the unionid mussels collected. Although few Lampsilis higginsi were found, mussel habitat in the Richmond Island area may be potentially important for Lampsilis higginsi. Evidence of this area's potential importance is supported by the presence of many other mussel species and its high mussel densities.