How does the DNR decide whether to aerate a lake to prevent winterkill of fish? The DNR does not aerate lakes, but they do issue permits to lake associations, counties and other local partners who want to aerate shallow lakes that are prone to winterkill due to lack of dissolved oxygen in the water. Public safety is the primary concern, so these permits require aerated parts of the lake to be clearly marked with thin ice signs and located away from high-traffic areas such as boat launches and snowmobile trails.
DNR fisheries and wildlife managers often provide guidance on whether or not aeration is a good idea for a given lake. Some shallow lakes are important habitat for water fowl, where fish compete with ducks and geese for food while stirring up sediment that can harm aquatic vegetation. In those cases natural winterkill of fish serves an important biological purpose. Marilyn Danks, DNR aeration program specialist.