Research Finds No Improvement In Mercury Levels In Northern Wisconsin Lakes

Mercury Levels Are Still High In 324 Lakes In The Ceded Territories

There are walleye eating advisories in 324 lakes in the Ceded Territories. Photo: Jerry Woody (CC-BY-SA).

An update to a map with fish mercury advisories in the Ceded Territories of Wisconsin, Michigan and Minnesota shows that not much has changed.

In all, 446 lakes have been tested in recent years by the tribes and Great Lakes Indian Fish and Wildlife Commission. GLIFWC environmental biologist Sara Moses said of those lakes, 324 have been color-coded with walleye eating advisories.

“We didn’t see a lot of changes,” said Moses. “We have almost 450 lakes on the maps and of those we only had changes in the color or the consumption advice for nine different lakes.”

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Four of those lakes had more mercury in the walleye, and five had less. She said mercury levels in the Great Lakes region had been declining since the 1970s until recently, when there was an uptick.

“There’s something going on, perhaps in how mercury is cycling in the environment or how the food webs are working, that’s causing this increase,” said Moses. “It’s not known yet what may be behind it.”

Moses said it’s vital to get this information to anglers and especially tribal members.

“Eating fish, harvesting fish, sharing fish is all part of their traditional lifeway and their identity,” said Moses. “It’s very important to the tribe.”

The study is part of a four-year $450,000 federal Great Lakes Restoration Initiative grant that runs out in October.