CALORIC DENSITIES OF 3 PREDATORY FISHES AND THEIR PREY IN LAKE OAHE, SOUTH-DAKOTA

We determined mean seasonal caloric density of walleye Stizostedion vi treum, chinook salmon Oncorhynchus tschawytscha, rainbow trout Oncorhy nchus mykiss and ten species of prey fish from Lake Oahe, South Dakota . Age 3 and older walleye, chinook salmon, and rainbow trout showed di stinct seasonal patterns in mean caloric density during May through Se ptember, 1994. Energy content of these fish was lowest during spring a nd 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 ca loric density were also observed for rainbow smelt Osmerus mordax, yel low perch Perca flavescens, spottail shiners Notropis hudsonius, and l ake herring Coregonus artedi. This study demonstrated that age and sea son contribute to the variability in the energy content of fish from L ake Oahe. Life history stage and season should be considered in energe tics studies of fishes.