Food habits of adult predators in Norris Reservoir during winter drawdown

A total of 968 adult predators were sampled from Norris Reservoir during two consecutive winter drawdown periods from November 1996 through March 1997 to document food habits. The species collected included 17 channel catfish (Ictalurus punctatus), 33 flathead catfish (Pylodictis olivaris), 344 largemouth bass (Micropterus salmoides), 165 smallmouth bass (M. dolomieu,/em\u3e), 119 spotted bass (M. punctulatus), 152 walleye (Stizostedion vitreum), 51 sauger (S. canadense), and 87 striped bass (Morone saxatilis). Approximately 45% (436) of the sampled fish contained prey organisms in the gut. Only 82% (360) of these could be utilized in the analysis, since digested items could not be accurately identified or quantitatively reported. Nine identifiable species of fish were found as prey items in the stomachs of the predators: largemouth bass, smallmouth bass, spotted bass, white crappie (Pomoxis annularis), black crappie (P. nigromaculatus), bluegill (Lepomis macrochirus), gizzard shad (Dorosoma cepedianum), threadfin shad (D. petenense), and alewife (Alosa pseudoharengus); the first six species listed have been designated as sport fish for the purpose of this discussion. Largemouth bass had the most diverse diet, consuming fish from all nine species groups, including crappie (5%), black bass (5%), and bluegill (13%). The predators with the next most diverse diets were spotted bass and sauger; both of these had fish remains from four and six species groups, respectively. Striped bass consumed primarily shad and alewives (98%); the only sport fish consumed were one bluegill and two unidentifiable centrarchids. Black bass and flathead catfish utilized crayfish (Orconectes rusticus and O. forceps) in substantial numbers (27% and 26%, respectively); aquatic insects were a relatively small part of channel catfish, black bass, and striped bass diets. The exceptions were one channel catfish containing 23 chironomids and one smallmouth bass containing 60 dipteran larvae. Clupeids were the most frequently consumed prey item. They comprised nearly 70% of all predator diet items, but were insignificant in flathead catfish and smallmouth bass diets. Centrarchids (sport fish) comprised 17% of all predator diet items but were not a significant item in channel catfish, walleye, and striped bass diets. Crayfish comprised 11% of all the prey items consumed. Based on the results of this study, it can be concluded that adult striped bass do not have a significant impact on young-of-year sport fish species during winter drawdown periods