An Evaluation Of Freshwater Mussels In The Lower Ohio River In Relation To The Olmstead Locks And Dam Project 1995 1996 And 1997 Studies

Surveys were conducted in 1995, 1996, and 1997 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 impacts of construction and operation of a new lock and dam at River Mile (RM) 964.4. The greatest focus has been on a mussel bed just downstream of the project. Density categories of 20, 20 to 50, and50 individuals per square meter are reasonable for delineating low-, moderate-, and high-density assemblages within this bed. Density>200 individuals per square meter is occasionally measured, but always describes a location heavily dominated by recent recruits. The native mussel community of the lower Ohio River is dominated by Fusconaia ebena. Dominance of this species was high at RM 967 (near Olmsted, IL), typically exceeding 80 percent of the community. At RM 957 (near Post Creek, IL), F. ebena is much less dominant (33 percent). Species richness is similar at both locations. The F. ebena population in the lower Ohio River is heavily dominated by a single-year class (probably 1990) of recent recruits. Prior to the exceptional recruitment in 1990, this population was dominated by a very abundant 1981 cohort.