By Michigan Department of Natural Resources
Alewife, small prey fish that reach 2 to 9 inches in length, are experiencing a seasonal die-off in Lake Michigan, an event that frequently occurred 20 to 60 years ago but has been rare in recent times.
Not native to the Great Lakes, alewife migrated from the Atlantic Ocean into the Great Lakes through the Welland Canal in the 1920s.
Alewife spend most of the year in deep, cold waters. In the spring and summer, they migrate to nearshore areas to spawn and search for food. Some alewife come out of winter in a weakened state and don’t tolerate changing conditions such as large temperature swings. The combination of poor over-winter condition, temperature changes and spawning stress cause the die-off.
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“The die-off is larger than normal this year and something we have not seen in years,” said Jay Wesley, Lake Michigan basin coordinator for the Michigan Department of Natural Resources. “We are seeing the die-off extend from Muskegon all the way up to Cross Village and out to the Beaver Island complex.”
The DNR is fully aware of the situation and believes this is a natural event and not caused by pollution or disease. Both state and federal agencies annually collect alewife to evaluate their condition and abundance in Lake Michigan.
For more information on die-offs (also known as fish kills) in Michigan, visit Michigan.gov/FishHealth. The public is welcome to report fish kills at Michigan.gov/EyesInTheField; such reports are valuable to the DNR’s ability to manage the state’s aquatic resources.
If you suspect a fish kill is due to non-natural causes, call the nearest DNR office or Michigan’s Pollution Emergency Alert System at 800-292-4706.