Spring thaw unveils signs of winterkill among Michigan's fish, aquatic wildlife
If you see dead fish and aquatic animals in ponds, streams and canals as the spring thaw settles in, you might have noticed a natural effect called winterkill.
"While such sights can be startling, the Department of Natural Resources reminds everyone that it is normal for winter conditions to cause some mortality of fish and other creatures such as turtles, frogs, toads and crayfish," the Michigan DNR office explained in an announcement issued Monday.
One of the places where winterkill was noticed lately is in the city of Lapeer in Michigan's Thumb Area. City officials reported Monday they had received several calls about dead fish in Rowden Park, which is the city's largest public park.
"Apparently, it's a totally normal early spring event," Lapeer officials said in their social media post, citing DNR as their source.
"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."
Fish can become easily stressed in winter, when feeding opportunities are lower, the DNR explained. With the low energy levels, they are less able to handle low oxygen levels caused by decaying plants and organic material.
Ice and snow covering water further reduces the daylight available to the water plants, and the cycle continues.
Basically, the fish suffocate from lack of oxygen in the water during winter.
While that can happen over a period of weeks of months, dead fish might not be noticed until lake ice thaws and breaks.
Should you wish to report a fish kill site in the wild, go to Michigan.gov/EyesInTheField.
If you suspect a fish kill is due to non-natural causes, you can call the nearest DNR office or Michigan's Pollution Emergency Alert System at 800-292-4706.
