Energy acquisition and allocation patterns of lake whitefish (Coregonus clupeaformis) are modified when dreissenids are present

Abstract

We evaluated the effects of dreissenid-induced food web changes on rates of lake whitefish ( Coregonus clupeaformis ) energy acquisition and allocation in North American populations. We used mass-balance models of lake whitefish growth and methylmercury accumulation in 17 populations with and without dreissenids present to estimate and contrast rates of activity (ACT), consumption (C) and conversion efficiency (V). Historical estimates were also generated for a single lake whitefish population during dreissenid establishment. Bioenergetic estimates from both scenarios were compared with densities of Diporeia , a historically important diet component of lake whitefish. Mean lake whitefish ACT and C estimates in populations with dreissenids were significantly greater: 1.3–2 times those of populations without dreissenids. Conversion efficiencies scaled positively and significantly, while C and ACT varied negatively and significantly with Diporeia abundance. Our results suggest that changes in lake whitefish activity may affect density estimates — and ultimately sustainable management quotas — for this species. Our results also show that reported declines in lake whitefish individual growth rates in South Bay, Lake Huron, can be explained by increased activity rates due to increased foraging activity in an energetically depleted prey community.