The Minnesota Department of Natural Resources is urging the public to use caution on lake ice as winter aeration systems operate on many lakes.

Aeration creates areas of thin ice and open water that are extremely hazardous to people and pets. The public should watch for the large orange and black warning signs at public access, and they should also respect the thin ice signs around areas of open water.

“We’re urging people to use caution anytime they venture onto lake ice, especially at night,” assistant regional fisheries manager Brian Schultz said. “Ice is never 100 percent safe, but extreme care should be taken on aerated lakes.”

The milder winter has allowed dissolved oxygen levels to remain high enough to support good fish survival rates, allowing many of the aeration systems to remain idle for the first half of winter.

“There are 260 lakes in Minnesota that are permitted to have aeration systems,” Schultz said. “In the south region, we have 86 lake aeration systems permitted. Right now 55 of those are operating.”

The updated list of aerated lakes and more information is available at mndnr.gov/eco/lakeaeration.

Aeration systems help prevent winterkill of fish populations on certain shallow lakes by adding oxygen to a refuge part of the lake. While winterkill can be distressing to some people, it can have the benefit of removing undesirable fish like common carp that may be degrading water quality or outcompeting native species. Aeration systems may not always be beneficial, as a solid winterkill can help reset a lake and allow DNR fisheries crews to stock desirable game fish.

A permit from the DNR is required to install and operate an aeration system. Permit holders must issue public notices, post warning signs and inspect the systems at least once every seven days. Liability insurance is generally required of private groups or citizens operating aeration systems in protected waters. DNR staff ensure permittees comply with all requirements and regularly inspect systems for safety. 

Some municipalities may have ordinances that prohibit entering into the thin ice marked area and/or prohibit the night use of motorized vehicles on lakes with aeration systems in operation.  These local regulations are often posted at accesses where they apply. 

Questions concerning aeration or thin ice can be answered by calling a  regional or area fisheries office or the DNR toll free 888-646-6367.