Lake Michigan Gillnet Lake Trout Assessment 1998-2003

Annual spring (May) and fall (late October through early November) gillnet assessment surveys were conducted by researchers at the USGS Great Lakes Science Center (GLSC) in northern Lake Michigan, including the Northern Refuge, between 1998-2023. Total length, weight, sex, maturity, and sea lamprey wounds were recorded for each lake trout and burbot caught in the gill nets. Lake trout were aged: (1) by decoding information on an extracted coded wire tag; (2) using fin clip information; or (3) enumerating annuli on a maxilla bone. Burbot were aged by enumerating annuli on an otolith. Catch of both lake trout and burbot have been recorded for each of the gill nets that have been set. To study the dynamics of the lake trout and burbot populations in the Northern Refuge, these gillnet survey data have been analyzed and the results interpreted.