Spatial variation in feeding ecology of age-0 lake whitefish Coregonus clupeaformis in Lake Huron

Age-0 lake whitefishCoregonus clupeaformisstomachs from western Lake Huron were examined in 2018 to evaluate spatial variation in feeding ecology. Overall, age-0 lake whitefish had narrow diet niches and similar feeding strategies across sites in western Lake Huron, with all sizes of age-0 lake whitefish specializing on one prey at each site, with some other prey eaten occasionally by most individuals as fish grew at some sites. Although prey selectivity and the dominant prey types varied among sites, feeding success was generally similar among sites for most sizes of fish. For fish collected in neuston nets (13-21 mm), food biomass per fish did not differ between Saginaw Bay and Thunder Bay for fish that had lost their yolk sac even though cyclopoid copepods were selected in Saginaw Bay and calanoid copepods were selected in Thunder Bay, suggesting that the type of copepod available to early stage age-0 lake whitefish might not be as important as previously thought. Fish from beach seines (20-51 mm) also had a narrow diet niche with a fair degree of diet specialization on calanoids, cyclopoids, orBosmina, depending on site, along with generalized feeding on chironomid pupae at some sites. Selectivity patterns on zooplankton prey by larger age-0 fish followed patterns in prey availability, indicating the ability to adapt to prevailing prey conditions. Despite these spatial differences in prey importance, most fish had food in their stomachs and food biomass per fish did not differ among sites for most size groups, suggesting that variable diet patterns might not result in differential conditions for growth or survival of age age-0 lake whitefish. Adaptability in prey use might not entirely buffer age-0 lake whitefish from environmental variability, as we noted strong differences in both diet composition and feeding success among years (2014-2018) at the Monaghan Point site.