The effect of foraging by largemouth bass fry (Micropterus salmoides) upon invertebrates associated with aquatic macrophytes was determined using six 4m2 exclosures in Cochran Lake, Michigan during June 1978. The cladoceran Sida crystallina rapidly declined in exclosures with fry, but increased in control exclosures without fry. Chironomids and chydorids showed little change in the exclosures. Invertebrate populations and foraging by fry were also monitored in the lake during 1976 and 1979. Sida declined rapidly in June of both years. In 1979, a decline from 2200 to 300 individuals per m2 and a sharp drop in the proportion of adults between 19 and 22 June of both years, while chydorids bacame increasingly abundant in mid-summer and showed no evidence of depletion by the fish. These results suggest that populations of certain prey, which are found locally in high densities in the littoral zone, may be highly susceptible to brief episodes of intense predation by fish fry.