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DNR reminds people of 'startling' fish kills that may arrive after spring thaw

DNR: 'Startling' fish kills are normal during spring thaw in Michigan
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The Michigan Department of Natural Resources is reminding people that they may be more likely to discover dead fish or other aquatic animals as the spring thaw happens.

According to the DNR, winter conditions can cause fish and other creatures such as turtles, frogs, toads and crayfish to die.

“Winterkill is the most common type of fish kill," said Aaron Switzer, DNR Fish Production Program manager. "It can be particularly common in shallow lakes, ponds, streams and canals during seasonal changes. It’s a natural phenomenon, and these kills are localized. They typically do not affect the overall health of fish populations or fishing quality.”

The DNR said shallow lakes with excess aquatic vegetation and soft bottoms are more prone to the problem.

The fish and other aquatic life typically die in late winter but may not be found until about a month after the ice leaves lakes. That's because dead fish and other aquatic life are temporarily preserved by cold water.

“If you see dead fish as a result of winterkill, the fish may appear fuzzy. This is because of secondary infection by fungus, but the fungus was not the cause of death,” said Switzer. “The fish actually suffocated from a lack of dissolved oxygen from decaying plants and dead aquatic animals under the ice.”