Disturbance of the predator-prey relationship may result in increased angler success and may sometimes provide an effective management tool. Exceptional harvest of walleyes (Stizostedion vitreum) in Clear Lake, Iowa, in 1951 is perhaps explained by reproductive failure of yellow perch (Perca flavescens) in 1950 and by elimination of young yellow bass (Morone interrupta) through more than normal predation. Stocking of 5 northern pike (Esox lucius) per acre in the fall of 1953 increased the weight of the predator population by about 10 percent In the first 6 weeks of the next fishing season, over 20 percent of the stocked northerns were caught by anglers.