A limited commercial gill-net fishery for walleyes (Stizostedion vitreum vitreum) in New York waters of Lake Erie was established in the 1950's. Since then year class strengths have varied considerably; four have been outstanding- those of 1959, 1962, 1964, and 1971. A rapid rate of rise in water temperature during spawning and incubation was positively correlated with the strength of these year classes. Each time a strong year class appeared, small-mesh gill-net effort was markedly increased, and an average of 46% of the fish of each year class was harvested at age I before they were sexually mature. If the smallmesh gill-net fishery had not been operating, the total annual production by the largemesh gill-net fishery could have been increased by an average of 35%.