C. C. Bonds and J. J. Ney, Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0321

Abstract. Gizzard shad, illegally introduced into Claytor Lake, Virginia, in the late 1980's, have expanded to comprise more than one-third of fish biomass, but their benefit as a prey resource has not been determined. We collected piscivores (stocked striped and hybrid striped bass, walleye, and three black bass species) by electrofishing and gillnetting over a 1-year period to describe their seasonal diets. The moronid species and walleye fed heavily on gizzard shad in spring and fall; shad constituted as much as 85% by weight of stomach contents of these pelagic piscivores on a seasonal basis. The largemouth bass diet included 40% shad in spring and fall, but <10% on gizzard shad during summer months. Only age-0 gizzard shad were eaten by even the largest sportfish. The seasonal pattern of shad consumption thus reflects the morphological and distributional availability of young-of-year gizzard shad. Shad seasonally supplanted alewife in the diets of pelagic piscivores and largemouth bass. The effect of this dietary shift on sportfish growth remains to be determined.