Great Lakes / Water Quality

Scientists puzzled by mercury’s jump in Great Lakes fish

A staff member with the Michigan Department of Natural Resources Fisheries Division nets musky on Lake St. Clair in a 2009 photo. As the DNR conducts fish surveys, some of the catch are shared with the Department of Environmental Quality for analysis of the levels of mercury and other toxins in the fish’s tissues (Credit: Michigan Department of Environmental Quality).

DETROIT, MI — “It’s not supposed to be like this.

Though advisories about toxic mercury in fish have continued in Michigan and the surrounding Great Lakes, with recommendations to limit consumption of certain species to a few times per month, the amount of mercury found in fish tissues has dropped steadily over decades since the 1970s. That corresponded with the reduction of pollution coming from Midwestern smokestacks as regulations tightened, pollution prevention technology improved, and coal-fired factories and power plants went offline.

But over the last several years, that started changing. Scientists are finding mercury levels rising in large Great Lakes fish such as walleye and lake trout. Curiously, it’s occurring with fish in some locations but not others. Researchers are still trying to figure out why.”

— Keith Matheny, Detroit Free Press

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