Mercury Maps

Guidance for Safe Consumption of Walleye from Inland Lakes within the Ceded Territories of Wisconsin, Michigan, and Minnesota

The harvest of ogaa (walleye) from inland lakes is an important part of the Anishinaabe lifeway. By participating in the spring and winter spearing seasons, tribal members reaffirm their off-reservation treaty harvest rights while providing their families with a nutritious food source. Yet, along with this tradition often comes a concern about exposure to mercury through consumption of fish. GLIFWC’s Mercury Maps are available to help tribal members make informed choices that allow continued ogaa consumption while reducing their exposure to mercury. The maps provide the facts about mercury levels in ogaa in ceded territory waters where member tribes commonly harvest these fish.

How to Use the Mercury Maps

Mercury Maps are available below for the six GLIFWC member tribes in Wisconsin as well as the 1837 ceded territory of Minnesota and portions of the 1842 ceded territory of Michigan. The Mercury Maps for Wisconsin and Michigan show the lakes from which ogaa are typically harvested by a given member tribe. The Minnesota map shows all lakes in the 1837 ceded territory of Minnesota that are available for tribal harvest. The top map applies to women of childbearing age and children under 15 years of age. The bottom map applies to the remainder of the population, men 15 years of age and older and women beyond childbearing age. Each lake on the map is color coded to display how many meals of walleye per month from that lake have been deemed safe to eat. As can be seen on the two maps, fewer meals are recommended for children under the age of 15 and women of childbearing age in order to protect the developing brain of the fetus or child from the potential detrimental effects of mercury.

Bad River	Lac Courte Oreilles	Lac du Flambeau	Mole Lake

Red Cliff	St. Croix	Minnesota	Michigan

Suggestions for Reducing Mercury Exposure

There are a number of ways to reduce exposure to mercury while still harvesting and consuming ogaa:

Sort and label ogaa prior to freezing
- Put ogaa under 20 inches in bags labeled "under 20 inches"
- Put ogaa over 20 inches in bags labeled "over 20 inches"
- Label bags with the name of the lake where the fish were harvested
Follow the advice provided on the mercury maps for the maximum safe number of ogaa meals per month
Eat smaller ogaa (those under 20 inches) and ogaa from lakes with lower mercury levels such as those lakes color-coded blue or green

Alternatively, tribal members can choose to eat safer giigoonh (fish) species known to contain less mercury. Giigoonh such as walleye, muskellunge, largemouth bass, smallmouth bass, and northen pike generally contain more mercury than other giigoonh such as lake whitefish, herring, bluegill, crappie, perch, or sunfish.

Fish contain a number of nutrients that are critical to good health. By making informed desicions about the size and species of fish eaten and the lake from which those fish are harvested, tribal members can safely eat ogaa and other giigoonh as a part of a healthy diet.

In an effort to best serve our member tribes, the Environmental Section will continue to modify the information presented on the maps as science in this area advances and additional ogaa mercury data become avavilable.