Species of forage fish in stomachs of walleye and their abundance in trawl catches were compared in 1968–71. Young yellow perch were the predominant species in trawls and were consistently selected by walleyes. Consumption of young white perch and walleyes by older walleyes increased during periods of low yellow perch abundance which suggested that young yellow perch might act as a buffer controlling intensity of predation. This possibility was assessed by comparison of relative survival of white perch and walleye cohorts between the first and second year of life with indices of yellow perch density between 1959 and 1970. Close correlations between these variables support the conclusion that abundance of young perch governs intensity of predation on other forage size fish and indirectly controls the size of the walleye population by regulating cannibalism.