DNR reports highest alewife mortality in a decade

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GRAND RAPIDS, Mich. (WOOD) — The Michigan Department of Natural Resources says Lake Michigan experiences significant seasonal gaspereau mortality — something that was common in parts of the 20th century but is relatively rare now.

“Mortality is higher than normal this year and something we haven’t seen in years,” Jay Wesley, Lake Michigan basin coordinator for Michigan DNR, said in a statement. “We see mortality extending from Muskegon all the way to Cross Village and all the way to the Beaver Island complex.”

The good news is that DNR officials say there is no evidence that mortality is exacerbated by pollution or disease; all evidence points to a natural event.

Heather Hettinger, DNR Fisheries Management Biologist, told the Traverse City Record-Eagle that mass mortality is linked to climate change and the alewife’s emphasis on spawning.

“As the snow and ice melt and spring sets in across northern Michigan, there are usually rapid changes in temperature. Also in the spring, alewife come to the shores of the lake to spawn,” said Hettinger to the Record-Eagle. “Between climate change affecting water temperature and the hyper-concentration of alewife on spawning, fish are getting caught in waters where they cannot properly regulate their body temperature, which which causes them to die in large numbers.”

The gaspereau is a small prey fish which can reach up to 9 inches in length. They are not native to the Great Lakes. Scientists believe gaspereau migrated from the Atlantic Ocean to the Great Lakes through the Welland Canal in the 1920s and 1930s.

By the 1950s and without key predators to control the population, gaspereau dominated Lake Michigan, Lake Huron and Lake Ontario. According to Hettinger, coastal towns would use heavy equipment to remove mounds of dead fish from beaches.

DNR started store more salmon in Lake Michigan, which has helped to reduce the population and limit the impact of deaths.

“Alewife has become quite an important forage species over the years, especially for fish like chinook salmon, coho salmon, rainbow trout, brown trout,” Hettinger told the Record-Eagle. “There are a lot of fish that use them in their diet.”

MNR officials say that if you spot a fish kill and suspect it is due to unnatural causes, call the nearest MNR office Where Michigan Pollution Emergency Alert System at 800.292.4706.

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