Food Habits and Diet Overlap of Age-1 and Older Walleye and White Bass in Lake Poinsett, South Dakota

White bass Marone chysops and walleye Stizostedion vitreum coexist in several of the large glacial lakes in eastern South Dakota. I collected age-1 and older white bass and walleye in Lake Poinsett, South Dakota during May, July and September, 1998 to determine food habits and diet overlap using percent by weight to describe diets and Schoener\u27s index (Cxy) to determine diet overlap. Macroinvertebrates were common prey items for white bass in all length groups during all sample dates. The primary macroinvertebrates consumed by white bass were corixids, amphipods and dipterans. Fish, as a group, were second in diet importance over all sample dates and length groups. Consumption of fishes increased with fish length for all sample dates. Common fishes found in the diets of white bass were fathead minnows Pimephales promelas and darters Etheostoma spp. Unidentified fish were the most abundant prey fish group in the diets over all sample dates. Zooplankton (primarily Daphnia) composed a small portion of the diet of white bass for all sample periods and length groups except for the 120- to 250-mm length group during July and the 250- to 349-mm length group during September when zooplankton composed 23.8 and 40.1 % of the diet by weight, respectively. Macroinvertebrates were the most abundant prey item during May and July for all length groups except during September for 250- to 379-mm and �380-mm walleye where fish were most abundant. Dipterans and amphipods were the most abundant macroinvertebrates in the diets of walleye. Fishes were also an abundant prey item in the diets of walleye. Common fishes in the diets of walleye were fathead minnows and darters. Zooplankton were only found in the diets of walleye in trace amounts and did not substantially contribute to the diets of any length group or sample date. Diet overlap values were ≥ 40% among white bass length groups in May, then decreased in July with only one value above 40%. In September, all values were again 40%. Diet overlap trends for walleye length groups were similar to those of white bass with the seasonal low in July. Diet overlap values among walleye length groups were higher than those for white bass for all sample dates. Diet overlap between walleye and white bass was at a seasonal high during May and declined throughout the summer. In both May and September, diet overlap decreased as fish length increased. Diet overlap values above 60% only occurred in May