Toxicological effects of methylmercury on walleye (Sander vitreus) and perch (Perca flavescens) from lakes of the boreal forest

Biochemical and physiological responses of walleye (Sander vitreus) and perch (Perca flavescens) were studied in four Canadian boreal forest lakes representing a mercury (Hg) exposure gradient. The aim of this study was to assess the effects of Hg and methylmercury (MeHg) on the general physiological condition of fish as well as to gauge the relationship between MeHg and the glutathione (GSH) system in metal-contaminated and reference sites using a series of biomarkers. Walleye from Lake Malartic had the highest liver MeHg concentrations, exhibited lower hepatosomatic indices (HSI) and lower glutathione S-transferase (GST) activity. HSI was negatively related to liver total Hg concentrations in walleye (R2 = 0.33, n = 108, P < 0.0001). Glutathione reductase (GR) and GST activity for walleye from Lake Malartic were related to HSI (R2 = 0.38, n = 25, P = 0.0010; R2 = 0.46, n = 27, P < 0.0001, respectively). In Lake Desjardins-East, where perch had the highest liver MeHg concentrations, glutathione peroxidase selenium dependent activity (GSH-Px SD) and GST activity were negatively related to liver MeHg concentrations (R2 = 0.39, n = 21, P = 0.0026; R2 = 0.22, n = 21, P = 0.0298, respectively). This study suggests that Hg may induce adverse effects on the physiology and cellular metabolism of walleye and perch at environmentally relevant concentrations.