DNR: 'Startling' fish kills are normal during spring thaw in Michigan

Posted at 10:37 AM, Mar 21, 2022
and last updated 2022-03-21 10:37:26-04

(WXYZ) — The Michigan Department of Natural Resources is reminding people that finding fish kills and other dead aquatic animals is normal during a spring thaw.

Despite the sights being startling, it is more likely for people to discover dead fish and other aquatic animals after winter, as conditions during the winter can cause fish and other creatures like turtles, frogs, toads and crayfish, to die.

Shallow lakes and soft bottoms are more prone to this happening, according to the DNR.

"Winterkill is the most common type of fish kill," DNR Fisheries Division Research Manager Gary Whelan said in a statement. "As the season changes, it can be particularly common in shallow lakes, ponds, streams and canals. These kills are localized and typically do not affect the overall health of the fish populations or fishing quality."

The DNR reports that fish and other aquatic life typically die in the late winter, but may not be found until after the ice leaves, as they are temporarily preserved by the cold water.

Fish may also be affected by rapid changes in water temperatures, leading to stress and sometimes death.

"Winterkill begins with distressed fish gasping for air at holes in the ice and often ends with large numbers of dead fish that bloat as the water warms," Whelan said. "Dead fish and other aquatic life may appear fuzzy because of secondary infection by fungus, but the fungus was not the cause of death. The fish actually suffocated from a lack of dissolved oxygen from decaying plants and other dead aquatic animals under the ice."