Food Habits and Distribution of the Emerald Shiner, Notropis atherinoides Rafinesque, and the Spottail Shiner, Notropis hudsonius (Clinton), in Lake Oahe, South Dakota

Abundance, age/length relationships, and food habits were studied for the emerald shiner Notropis atherinoides and the spottail shiner Notropis hudsonius at three sites on Lake Oahe, South Dakota, in 1990. Emerald and spottail shiners were among the most abundant species sampled in beach seine hauls between May and September. Spottail shiners were occasionally caught in small mesh gill nets. Emerald shiners were common in the upper and middle reservoir but were rare near the lower end of Lake Oahe. Spottail shiners were captured in higher numbers by night seining than by daytime seining. Age groups 0-3 were present for both species. Emerald and spottail shiners ate primarily large zooplankton and insects. Both species showed a preference for Daphnia. Shifts in feeding from zooplankton to insects occurred for both species when zooplankton abundance was low. The diets of emerald and spottail shiners showed considerable overlap on several sampling dates, indicating possible competition. Emerald and spottail shiners provide a prey base for predator fish in Lake Oahe in habitats where the primary prey, rainbow smelt Osmerus mordax is scarce or absent