Lake Trout, Sea Lampreys, and Overfishing in the Upper Great Lakes: A Review and Reanalysis

To assess the role of commercial fishing in the destruction of lake trout Salvelinus namaycush in Lakes Huron, Michigan, and Superior in the 1940s and 1950s, we reviewed the literature and analyzed catch and effort data for U.S. waters by regression analysis. There is abundant evidence of the effect of the sea lamprey Petromyzon marinus in the destruction of lake trout, but some have claimed that fishing also was influential. We considered that a persistent, significant decrease in catch per unit of effort before and in the first few years after the sea lamprey was first found in a lake would be evidence of overfishing. We found no convincing evidence of overfishing in Lakes Huron and Michigan. Lake trout probably were overfished in Lake Superior before the sea lamprey became a major influence. We conclude that statements that lake trout were destroyed in Lake Huron or Lake Michigan by a combination of overfishing and the sea lamprey are not justified. The same claim applied simply to the Great Lakes is ambiguous, for it may be construed that lake trout were overfished in all the lakes. More critical analysis of evidence for our beliefs and hypotheses is recommended.