Response of Littoral Fishes in Upper Lake Marion, South Carolina Following Hydrilla Control by Triploid Grass Carp

Abstract

A seven-year study in upper Lake Marion, South Carolina evaluated the response of fishes to hydrilla ( Hydrilla verticillata (L. f.) Royle) removal by triploid grass carp ( Ctenopharyngodon idella Valenciennes). A boat-mounted electroshocker was used to quantify relative abundance and species composition of fishes at 10 permanent locations distributed throughout the upper lake. A total of 16,306 fish representing 64 species were collected. The taxonomically dominant family was Centrarchidae and the numerically dominant family was Clupeidae. There were significant differences in catch between years with high and low hydrilla coverage. Littoral fishes, especially Centrarchidae, increased as hydrilla decreased from a maximum of 4,700 ha (approximately 50% of the surface area) to less than 100 ha by 1994. Mean lengths of most littoral species were similar during the study. Despite substantial declines in hydrilla, other forms of cover