Bioenergetics and growth of young-of the-year northern pike (Esox lucius) and burbot (Lota lota) exposed to metal mining effluent

We hypothesized that exposure to metal mining effluent would reduce the ability of young-of-the-year fishes to accumulate energy reserves to survive the overwinter period (known as “winter stress syndrome”) in a Canadian boreal forest watershed. Northern pike (Esox lucius) and burbot (Lota lota) were collected immediately before and after winter from a reference lake and two lakes receiving effluent. Unexpectedly, total body lipid and triglyceride, and liver triglyceride levels were greater in effluent-exposed pike and burbot in both fall and spring. However, there were no lake or season differences in growth indices of length, weight, muscle RNA/DNA ratio, or muscle protein levels in pike. In addition, total lipids and triglycerides in burbot were greater in spring compared to fall, while no seasonal differences were observed in pike, suggesting that burbot continued to feed during winter. Findings do not support the winter stress syndrome hypothesis and suggest possible direct and indirect effects of metal mining effluent on lipid dynamics of juvenile fishes.