James B. Sickel, Jeffrey J. Herod, and Darren P. Reed, Department of Biological Sciences, Murray State University, Murray, KY 42071

Abstract. Native unionid mussels in western Kentucky have been examined over the past 20 years with three major surveys in Kentucky Lake: 1980-81, 1988-89, and 1995-96; one major survey in Lake Barkley in 1994; and numerous minor studies in the lower Cumberland River, Tennessee River and Ohio River. The progress of the zebra mussel invasion in the lower Ohio River has been examined since its first appearance in 1991. Significant changes in the Kentucky Lake unionid community are reflected in a reduction in density of some commercial species, especially Quadrula quadrula and Megalonaias nervosa, while some commercial species are experiencing successful reproduction and increase, e.g. Amblema plicata. We suggest that harvest size limits are too small for M. nervosa and Q. quadrula, while the limits for A. plicata are adequate. Although mortality of undersized mussels caught on brails averages 50%, and there has been a significant change in the community composition, the overall density of mussels has not changed significantly since 1980. Zebra mussels are attached in large numbers to essentially every unionid in the lower Ohio River, and mortality of unionids is now indicated. However, although their numbers are increasing, few zebra mussels occur in the Tennessee and Cumberland rivers. Supporting funds for this project were received from the Mussel Mitigation Trust, Murray State's Center for Reservoir Research and the Shell Exporters of America, Inc.