Alewife (Alosa pseudoharengus), are a small anadromous prey fish species that reach about 2 to 9 inches in length. Are experiencing a rare seasonal die-off in Lake Michigan this summer. These die-off events frequently occurred 20 to 60 years ago in Lake Michigan, but have been rare in recent times.
The alewife is not native to the Great Lakes system, they migrated in from the Atlantic Ocean. The alewife having passed through the Welland Canal back in the 1920s. They spend most the year in the deeper, cold waters of the great lakes. In the spring and summer, they migrate in large schools to the nearshore areas to spawn and feed in the shallower waters.
Some the alewife that made it through the winter have been weakened. This causes them to be more sensitive and not able to tolerate large changes in the conditions. Such as large temperature swings and water conditions. The combination of a poor over-winter condition, drastic temperature changes, and stress from spawning has caused a large die-off in Lake Michigan
“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 Michigan DNR is fully aware of the alewife situation and believes this is a natural event. Both state and federal agencies have annual alewife collections to evaluate the alewife stock. This is to evaluate the alewife population 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.