Dynamics of a Recovering Lake Trout Population in Eastern Wisconsin Waters of Lake Superior, 1980–2001

Abstract

Lake trout Salvelinus namaycush are important in Lake Superior because of their economic and ecological value. Lake trout populations collapsed in the early 1950s due to overexploitation by the commercial fishery and predation by sea lampreys Petromyzon marinus. Efforts to rehabilitate a self-sustaining lake trout population included stocking of hatchery-reared lake trout, control of sea lamprey populations, and closure of the lake trout fishery. To quantify and describe the dynamics of the recovering lake trout population in eastern Wisconsin waters of Lake Superior between 1980 and 2001, we used statistical catch-at-age analysis to estimate abundance, recruitment, mortality, and fishery selectivity of wild and stocked lake trout. We found that estimated wild lake trout abundance increased, whereas estimated stocked lake trout abundance decreased. Estimated wild lake trout recruitment was erratic, while estimated stocked lake trout recruitment decreased until stocking was discontinued in 1996. Natural mortality was the largest component of estimated wild lake trout total mortality, where commercial fishing mortality was the largest component of estimated stocked lake trout total mortality. Wild lake trout abundance in Wisconsin waters of Lake Superior is on par with precollapse abundance levels, and total mortality rates are below rehabilitation target levels; however, wild lake trout recruitment is still below the level thought necessary to sustain the population.