Stomachs of black and white crappies (Pomoxis nigromaculatus and P. annularis) collected during the early impoundment (1964-1967) and the late impoundment (1969-70) periods from Beaver Reservoir were analyzed. Black crappie were dominant in the early impoundment period, whereas white crappie was the dominant crappie species in the late impoundment period. During the early impoundment period, large numbers of earthworms (January to April) and shad (during the remainder of the year) were consumed by both species, although white crappie appeared to concentrate on shad even when earthworms were available. During the late impoundment period O-age fishes, zooplankton, and aquatic insects comprised the diet of both species. However, white crappie adults concentrated on fishes all year round, whereas black crappie adults concentrated on benthic insects in the spring and fishes in other seasons. The availability of earthworms and benthic insects in the early impoundment period and their lack of availability in the late impoundment period, along with the deterioration of much of the submerged terrestrial vegetation, appear to have been the major factors in determining the dominance of the two crappies.