Feeding Ecology of Fishes in a South Dakota Power Plant Cooling Reservoir

The food habits of bluegills (Lepomis macrochirus), black bullheads Ictalurus melas), and muskellunge (Esox masquinongv) in the Big Stone Power Plant cooling reservoir were studied from January through December 1979. The diet of 794 bluegills \u3e50 mm TL was dominated by vegetation, planktonic crustaceans, dipteran larvae and pupae, and fishes: 214 bluegills \u3c 50 mm TL fed primarily upon chironomid larvae and pupae and cladocerans. There was a significant difference (P50 mm. This was determined by Spearman rank correlation coefficients based upon percent number and percent volume of food items, and mean number of taxa per stomach. Both bluegill length-groups positively selected Chydorinae, ostracods, Caenis spp. larvae, chironomid pupae, and Physa spp., while they negatively selected cyclopoid copepods, Ceriodaphnia spp., and Tanypodinae larvae. Chironomid larvae were positively selected by bluegills mm, but were negatively selected by those \u3e50 mm. Fishes and chironomid larvae were the major food items of 105 black bullheads \u3e120 mm TL; fishes and filamentous algae were the dominant food items of 146 bullheads 5120 mm. Ostracods and dipteran pupae were positively selected, while Tanvpodinae and Chironominae larvae were negatively selected. Chydorinae, cyclopoid copepods, and Physa spp. were negatively selected by bullheads \u3e120 mm. Chydorinae and Physa spp. were positively selected and cyclopoid copepods were ingested in proportions equal to those in the environment by bullheads X120 mm. The diet of 107 yearling and young-of-the-year muskellunge was dominated by Johnny darters (Etheostoma nigrum), fathead minnows (Pimephales promelas), and centrarchids (Lepomis spp.). There were positive correlations between jaw width (closed) of muskellunge and prey size (total length and body depth); and body depth of muskellunge and prey size