Mercury levels grow in Lake Erie fish

Toronto, ON – Mercury levels in a popular species of game fish in Lake Erie are increasing after two decades of steady decline, Ontario Ministry of Environment scientists are reporting. The study, the most comprehensive to date on mercury levels in Great Lakes fish, was published online on March 30 in the American Chemical Society’s Environmental Science & Technology.

Dr Satyendra Bhavsar and colleagues note that although government regulations and improved emissions control technologies have greatly reduced mercury emissions in the environment, their impact on mercury levels in Great Lakes fish is unclear.

The scientists studied mercury levels in 5,807 fish samples collected from the lakes between the 1970s and 2007. The samples included lake trout and walleye, two of the most common species of game fish caught in the region. The researchers found that mercury levels in the fish steadily declined from the mid-1970s to 2007 in the upper Great Lakes (Superior and Huron). In recent years (between 1990 and 2007), however, the mercury concentrations levelled-off in Lake Ontario fish but appear to be increasing in Lake Erie fish. The mercury increases are likely caused by a combination of factors, including modifications in Lake Erie’s foodweb due to invasions of dreissenid mussels and round goby, the scientists suggest.