Q: Why do alewives die along Lake Michigan beaches?

A: For any Great Lakes beachcomber, a common sight is the small silvery, herring-like fish known as the alewife. The alewife is an exotic species that can live in both fresh water and the ocean. The fish gained access to the Great Lakes with the opening of the St. Lawrence Seaway in 1959.

With no natural predators, alewife populations soared and massive spring die offs in the 1960s resulted in many Great Lakes beaches being covered in tons of dead, smelly fish.

Alewives spawn in the spring, and the combination of rapidly warming water temperatures and the physiological stress of spawning cause high mortality rates, according to UW-Madison limnologist James Kitchell.

"What we see on the beaches in the recent past is modest compared to the massive die-offs that occurred in the late '60s when tons of dead alewives appeared on the beaches and clogged water intakes," Kitchell explains.

In response to the problem, fishery managers started stocking Lake Michigan with salmon as a "biological control." That, Kitchell says, was a huge success, both in terms of reducing the overly abundant alewives and creating a billion-dollar sport fishery that continues to the present.

- Produced in cooperation with University Communications

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