Reproductive allocation in exploited lake whitefish (Coregonus clupeaformis) and walleye (Sander vitreus) populations

We examined age-related changes in energetic status and reproductive effort of lake whitefish (Coregonus clupeaformis) and walleye (Sander vitreus) populations in Lakes Winnipeg and Ontario. We predicted, based on life history theory, that both species would exhibit declines in somatic energy stores and increases in the proportion of their energy reserves allocated to reproduction as they aged. These predicted trends were evident for walleye but not for lake whitefish, and the contrast between species was most pronounced for females. Walleye devoted an increasingly larger proportion of their body lipids to gonad development as they got older whereas lake whitefish devoted an increasingly smaller proportion. Between-species differences for some reproductive traits, particularly gonad size (GSI) and relative fecundity, were not consistent between the two lakes. Lake whitefish follow a strategy of lower relative fecundity, larger eggs, and lower egg lipid content compared to walleye. Differences between these species in the gamete quantity and quality of different age classes suggest that age-structured population models parameterized for one species should be applied to other species with caution.