Recreation

Fish Consumption Advisory

Official guidance from state health departments recommending limits on eating fish from specific lakes due to mercury, PCBs, or other contaminants.

What It Means for Your Lake

Fish consumption advisories are public health recommendations issued by the Minnesota Department of Health (MDH) and the Wisconsin Department of Natural Resources (DNR) that specify how often fish from specific water bodies can be safely eaten based on measured levels of contaminants in fish tissue. The primary contaminants triggering advisories in Minnesota and Wisconsin are mercury (a neurotoxin that bioaccumulates in fish, particularly in predatory species at the top of the food chain) and polychlorinated biphenyls (PCBs, industrial chemicals that persist in the environment and accumulate in fatty tissue). Mercury enters lakes primarily through atmospheric deposition, coal-burning power plants and industrial facilities release mercury into the air, which is deposited on land and water surfaces by rain and snow. Once in lake sediment, bacteria convert inorganic mercury to methylmercury, which is readily absorbed by organisms and biomagnifies up the food chain. Large predatory fish like walleye, northern pike, and musky accumulate the highest mercury levels. Statewide advisories in both Minnesota and Wisconsin recommend limiting consumption of predatory fish, with more protective guidelines for women of childbearing age and children under 15. Lake-specific advisories provide tailored guidance based on actual fish tissue testing, some lakes have elevated mercury levels due to water chemistry (low pH and high dissolved organic carbon enhance mercury methylation), while others have very low levels. PCB advisories are concentrated in lakes and rivers near former industrial sites, particularly in the Fox River valley of Wisconsin and the St. Louis River estuary in Duluth. Fish consumption advisories are distinct from water quality grades, a lake can have excellent water clarity and an A grade while still having mercury advisories for its fish, because mercury contamination comes from atmospheric sources rather than local nutrient pollution.

Frequently Asked Questions