Lake Michigan awash in seasonal alewife die-off, DNR says

Visitors flocking to Lake Michigan beaches this summer are seeing unusual pileups of dead fish, thanks to changing water conditions, state officials said Wednesday.

Alewife, small prey fish that reach 2-9 inches long, are amid a seasonal die-off in the lake, the Michigan Department of Natural Resources reported.

Both state and federal agencies annually collect alewife to evaluate their condition and abundance in Lake Michigan. The die-off "frequently occurred 20 to 60 years ago but has been rare in recent times," department officials said in a statement.

Alewife migrated from the Atlantic Ocean into the Great Lakes through Canada's Welland Canal in the 1920s.

The fish spend most of the year in deep, cold waters then move to nearshore areas each spring and summer to spawn and seek food, the DNR said. 

Some emerge weak and cannot tolerate changing conditions such as large temperature swings.

The DNR believes a combination of poor over-winter condition, temperature changes and spawning stress cause the die-off, not pollution or disease.

“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.”