David C. Cray and Deanna J. Stouder, Ohio Cooperative Fish and Wildlife Research Unit, The Ohio State University, 1735 Neil Avenue, Columbus, OH 43210

Abstract. The completion of the lock and dam system on the Ohio River in 1929 turned a once free-flowing river into a series of pools, flooded tributary mouths, and created the current set of embayments. Currently, 124 embayments exist along the Ohio side of the Ohio river however, few remain relatively unaltered. Between Parkersburg, WV and Cincinnati, OH, we only found six embayments in this condition. Because these habitats are extremely rare and imperiled, it is essential to understand the role these habitats play in supporting riverine fish assemblages. From April through October 1997, we sampled fishes (using electroshocking and gill nets) in up-, mid-, and downstream locations within each embayment to evaluate spatial and temporal patterns of fish assemblage structure. Fish density increases over time. For example, most young Micropterus spp. recruited to our sites in August. At the same time Dorosoma cepedianum densities increased dramatically. Up- and mid-stream fish assemblages appeared most similar. Shallow versus deep embayments harbored slightly different fishes. GIS coverages allowed us to assess the influences of physical characteristics on biological components of these habitats. This information will provide managers with the tools to evaluate the importance of this resource to fishes along the Ohio River.