Temporal patterns of change in growth, condition, and mean age of samples of lake whitefish (Coregonus clupeaformis) taken from Lesser Slave Lake, Alberta, during 1941–75 are described. Growth rate and condition have declined, while mean age has increased. Gillnet fisheries are highly selective of large, heavy, fast-growing individuals, and we suggest that culling of this sort will provoke an evolutionary response in the stock, which may be reflected in patterns of change in growth and age. This hypothesis and others are discussed, and the general importance of artificial selection in lake fisheries is briefly considered. The possible implications for fishery management are outlined. Key words: artificial selection, evolution, growth rate, gillnet, Coregonus clupeaformis.