Freshwater Mussels In The Lower Ohio River In Relation To The Olmsted Locks And Dam Project Update Through 2001 Studies

Surveys were conducted in the summers of 2000 and 2001 to assess community characteristics, population demography of dominant species, status of endangered species, and characteristics of nonindigenous populations of freshwater bivalves in the lower Ohio River. Data will be used to analyze ecological effects of construction and operation of a new lock and dam at River Mile (RM) 964.4. Primary focus has been on a prominent mussel bed just downstream of the project at Olmsted, IL. Studies have shown that this mussel bed extends approximately from elevation 278 ft nearshore to 267 ft farshore. Moderate (20 to 50 individuals/sq m) or high density (>50 individuals/sq m) assemblages of mussels tend to be located at more central elevations on the bed from approximately RM 966.4 to 968.3. The downstream and farshore limits of the mussel bed tend to be less distinct than the nearshore and upstream limits. The community downstream of the project is extremely dominated by Fusconaia ebena. A mussel bed being monitored upstream of the project, at RM 957 near Post Creek, is clearly dominated by this species, but much less heavily than at Olmsted. Also, the abundance of F. ebena is higher farshore than nearshore at the Post Creek site. Communities at both Olmsted and Post Creek have been resilient to long-term occurrence (since approximately 1960) of the Asiatic clam, Corbicula fluminea, and more recent occurrence of the zebra mussel, Dreissena polymorpha. Both mussel beds are characterized by extreme dominance of a few year classes (especially 1981, 1990, and 1998) of the dominant species. Rapid spring rises in discharge from unseasonally low values occurred in combination with rising water temperatures in spring of all three good recruitment years. These conditions may trigger spawning runs by F. ebena's host fish, Alosa chrysochloris (skipjack herring).