The effects of feeding ecology on mercury accumulation in walleye (<i>Stizostedion vitreum</i>) and pike (<i>Esox lucius</i>) in Lake Simcoe

Abstract

In Lake Simcoe, mercury was accumulated by walleye to a greater maximum concentration (2700 ng g −1 ) and at a faster rate (119 ng g −1 year −1 ) than pike (maximum concentration, 850 ng g −1 ; rate, 78 ng g −1 year −1 ). Field studies showed that relative to pike, the total diet of walleye was more highly mercury contaminated primarily because it contained a higher proportion of smelt, the most highly contaminated prey for either predator. Additionally, as walleye and pike became older, their prey became larger and the species composition changed. Consequently, as they grew older, the diet of these predators contained more mercury. Bioenergetic equations predicted that on an age-specific basis, walleye had a higher food consumption rate (grams of food per gram of fish per year) that pike and thus are predicted to consume more mercury with their diet than pike. This study supports the hypothesis that the diet of feral fish has a strong influence on the accumulation of mercury.