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

Abstract

Lake trout Salvelinus namaycush were historically important in Lake Superior due to their economic and ecological value. Lake trout populations collapsed in the early 1950s due to overexploitation by the commercial fishery and predation by sea lamprey Petromyzon marinus. Efforts to rehabilitate a naturally reproducing lake trout population included stocking of hatchery-reared lake trout, control of sea lamprey populations, and closure of the lake trout fishery. To understand the population dynamics of the recovering lake trout population in Wisconsin waters of Lake Superior between 1980 and 2001, I used statistical catch-at-age analysis to estimate abundance, recruitment, mortality, gear selectivity, catchability, and fishery harvest of lake trout. I found that estimated wild lake trout abundance increased, whereas estimated stocked lake trout abundance decreased. Estimated wild lake trout recruitment was erratic, whereas estimated stocked lake trout recruitment decreased until stocking was discontinued in 1996. Trends in estimated wild lake trout mortality were influenced by sea lamprey mortality, whereas trends in estimated stocked lake trout mortality were influenced by commercial fishing mortality. Estimated wild lake trout commercial fishery harvest declined, whereas estimated wild lake trout recreational harvest increased. Estimated stocked lake trout commercial fishery harvest declined, whereas estimated stocked lake trout recreational fishery harvest remained constant. Wild lake trout abundance should continue to increase and stocked lake trout abundance to decrease within Wisconsin waters of Lake Superior, if survival and recruitment of wild and stocked lake trout remains the same in the future as at present.