Grass Carp Movement in an Appalachian Reservoir

Triploid grass carp (Ctenopharyngodon idella) have been used as a biological control for nuisance vegetation such as hydrilla (Hydrilla verticillata) in numerous large reservoirs. In 2011, the Virginia Department of Game and Inland Fisheries (VDGIF) approved the introduction of triploid grass carp into Claytor Lake, VA to control a rapidly-expanding hydrilla infestation. Claytor Lake is an impoundment of the New River and has a hydrologic retention time of 63 days, and a shoreline development index of 10.65. Since grass carp are known to be highly migratory, VDGIF biologists are concerned grass carp will immigrate seasonally into the New River with high flows, thereby impacting the native vegetation. We initiated a multi-year telemetry study concurrent with grass carp stockings to investigate potential intra- and inter-system movement patterns in Claytor Lake and the New River. Tracking results from 2011 indicate that grass carp moved moderately post-stocking until hydrilla was located, at which time fish exhibited highly sedentary behavior during the growing season. Furthermore, multiple regression suggests grass carp movements can be predicted by variations in temperature and river discharge (R²=0.88, P=0.005). We anticipate this study will ultimately provide a valuable case study for managers contemplating grass carp stockings in similar environments.