Dead fish, other aquatic animals common sight during spring in Michigan -- What to know about fish kills

The public is welcome to report fish kills (a common sight during spring thaws) using the Eyes in the Field website; such reports are valuable to the DNR’s ability to manage the state’s aquatic resources. (Photo: DNR)

As ice and snow melt in Michigan, dead fish are a common sight.

You may see the fish, along with other aquatic animals, including turtles, frogs, toads, and crayfish near lakes. 

Fish can become easily stressed in winter due to low energy reserves due to minimum feedings, and temperature swings that make handling oxygen more difficult. The creatures seen in the spring may have died in late winter but are not obvious until the ice is gone.

"Winterkill is the most common type of fish kill," said Gary Whelan, the Michigan Department of Natural Resources Fisheries Division research manager. "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."

Shallow lakes with excess aquatic vegetation and soft bottoms are more prone to this problem, especially when there is a deep snowpack that reduced sunlight for the plants. 

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Canals in urban areas also often see these kills due to the large amounts of nutrient runoff and pollution from roads and lawns and septic systems that flow into these areas, especially when there are large storms.

"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."

Though these kills are common, if you are concerned about dead fish, report it to the DNR here, or call the nearest DNR office or Michigan's Pollution Emergency Alert System at 800-292-4706.