Dead fish may start showing up on the surface of Michigan’s shallow lakes and other waterways in the coming weeks.
The state Department of Natural Resources said that’s because oxygen levels in water can go down during the winter months — killing the fish. The dead fish then can rise to the surface once ice melts.
DNR Fisheries Division program manager Gary Whelan said the winterkill usually is done by early April.
“If people see continuing fish kill events, they see continually dead fish showing up that are fresh, not fungus-ed, or don’t have a fuzzy look to them, they should let us know,” he said. DNR offers a website for people to report issues.
Whelan said the winterkills typically don’t drastically affect fish populations.
“It varies a tremendous amount. It could be as high as 20 or 50% [of the population] in some lakes. In other lakes, it may be just 5% because it’s a small cove that’s affected.”
Though Whelan said winterkills are natural, there are things people who live near water can do if they notice fish kills happening frequently. He said managing runoff is often important.
“You should be thinking about ways to control nutrients off the landscape and off whatever’s feeding your particular water body. Because, undoubtedly, that’s what’s creating excess aquatic vegetation, and that aquatic vegetation is what’s creating the issues,” Whelan said.
Nitrogen and phosphorus from nutrient runoff can contribute to making fish kills happen more often.