Relationship between Mercury Concentration and Growth Rates for Walleyes, Northern Pike, and Lake Trout from Quebec Lakes

The relationship between mercury (Hg) concentrations in fish muscle and fish growth rates was assessed for 54 walleye Sander vitreus, 52 northern pike Esox lucius, and 35 lake trout Salvelinus namaycush populations throughout the Province of Quebec, Canada. We used the von Bertalanffy growth model to estimate the ages of fish specimens for a given length, and Hg concentrations in fish specimens at standardized length were determined via a quadratic regression model. Measured values of Hg concentrations in walleyes, northern pike, and lake trout were then correlated to the estimated age at standardized length for each population (375, 675, and 550 mm, respectively). A model-II regression was performed to describe the existing relationships. Growth rates were positively related to Hg concentrations in walleyes and northern pike (when three outliers were excluded), whereas no correlation was observed for lake trout. Our findings demonstrate that slower-growing walleyes and northern pike have higher Hg concentrations at standardized length. For these fish species, growth rate could be used as an integrated proxy to predict Hg concentration in fish muscle on a regional scale. Our findings support the contention that biodilution can be an important factor regulating mercury concentrations in fish. Thus, our findings suggest that proper control of fish growth rate through fishing pressure, lake ecology, and watershed management could be used by fisheries management authorities to minimize the toxic risk associated with Hg exposure from fish consumption.