Lake Whitefish Feeding habits and condition in Lake Michigan
Fagan, K.-A.; Koops, M.A.; Arts, M.T.; Sutton, T.M.; Power, M.
Lake whitefish (Coregonus clupeaformis) have experienced declines in condition in some areas of the Great Lakes. The hypothesis tested was that condition—in terms of relative weight, percent lipid and docosahexaenoic acid (DHA)—was greater in regions where larger proportions of high quality prey (e. g., Diporeia) were included in the diet. Samples of spawning lake whitefish from four regions around Lake Michigan (northwest, Naubinway, Elk Rapids and southeast) had distinct mean carbon and nitrogen stable isotope signatures. Lake whitefish may be using a variety of prey items, especially the Naubinway population where fish occupy the largest stable isotopic niche space. However, trophic niche width inferred from stable isotopes did not vary among regions. Relative weight was highest in the southeast and lowest for all northern regions. The mean measured lipid from lake whitefish dorsal, skinless, muscle biopsies were highest for northwest fish. DHA was significantly different among regions, with high mean values in Elk Rapids and the northwest. No correlations were found between stable isotope measures and condition metrics. The results suggest that lake whitefish are coping with declining Diporeia abundances by feeding on alternate prey. Overall results do not substantiate the hypothesis of a relationship between condition and prey use, although lake whitefish from Elk Rapids and the northwest had high quality prey and good condition.