Caloric Densities of Three Predatory Fishes and Their Prey in Lake Oahe, South Dakota

We determined mean seasonal caloric density of walleye Stizostedion vitreum, chinook salmon Oncorhynchus tschawytscha, rainbow trout Oncorhynchus mykiss and ten species of prey fish from Lake Oahe, South Dakota. Age 3 and older walleye, chinook salmon, and rainbow trout showed distinct seasonal patterns in mean caloric density during May through September, 1994. Energy content of these fish was lowest during spring and highest during fall. No seasonal pattern in mean caloric density of ages 1 and 2 walleye, chinook salmon, and rainbow trout was observed, but caloric content differed among months. Seasonal differences in caloric density were also observed for rainbow smelt Osmerus mordax, yellow perch Perca flavescens, spottail shiners Notropis hudsonius, and lake herring Coregonus artedi. This study demonstrated that age and season contribute to the variability in the energy content of fish from Lake Oahe. Life history stage and season should be considered in energetics studies of fishes.