The logistic surplus production model is applied to the lake trout (Salvelinus namaycush) fishery of district MS-4 in Lake Superior from 1929 to 1950. Comparison of the equilibrium stock production curve with observed yield and effort data indicates that the fishery became overexploited at about the same time that the sea lamprey first was observed in the lake. This was a period during which fishermen were moving to Lake Superior from the other lakes as lake trout stocks were collapsing as a result of sea lamprey predation. The sharp decline in lake trout yields from Lake Superior occurred about 10 yr later. Collapse of the lake trout stocks apparently was caused by sea lamprey predation on a population that was stressed by intensive exploitation.
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