Thursday, April 4, 2024

What Happened to all the Alewives in Lake Michigan?

Alewives are small fish native to saltwater but migrate to freshwater rivers and streams to spawn. They are also called River Herring, Sawbelly, Gaspereau, and Kyak. Alewives are a type of herring similar to Atlantic herring and are a good source of protein and omega-3s.
Small Alewive (Herrings) Quickly Grow to Maturity.

Alewives, a non-native species, entered the Great Lakes through canals, lacking natural predators, allowing their numbers to explode.

In the 1960s, the government began a program to restore the balance of the Great Lakes ecosystem. With the intentional introduction of predators to control the exploding alewife population, non-native salmon species like Coho and Chinook were introduced into the Great Lakes. These salmon preyed heavily on alewives, bringing their numbers down significantly.

Alewives primarily fed on zooplankton. A reduction of zooplankton populations in Lake Michigan due to invasive zebra and quagga mussels also contributed to their decline by limiting their food supply.

Eventually, the alewife population reached a more balanced level within the Lake Michigan ecosystem. While die-offs still can occur, they are far less frequent and much smaller than the massive beaching events of the 1950s through the 60s.

Alewives are sensitive to sudden temperature changes. Cold weather snaps following warmer periods could shock massive numbers of fish, leading to die-offs. 
Thousands of alewives cover a beach near downtown Chicago after being washed ashore by Easterly winds. Migrants from salt water, the fish pack Lake Michigan. After they spawn, they die. Chicago Park District crews have the messy, smelly job of clearing the beaches and freshening the air.

The sheer vastness of their population meant that these die-offs resulted in millions of dead fish washing ashore, creating a foul-smelling mess on Chicago's beaches.

Alewives are still present in the Great Lakes but in much lower numbers.

Compiled by Dr. Neil Gale, Ph.D.


  1. Thanks for the info. Any idea what happened to the smelt?

  2. Introduction of Salmon in 60's - 70's: A salmon fishery finally was established when 15 million coho salmon and 6 million chinook salmon were planted as smolt in the Great Lakes in 1966-70. In 1970, for example, 576,000 coho salmon (12% of those planted in 1969) were caught by anglers in Lake Michigan. Most weighed 5 to 10 pounds (2.3-4.5 kg).

  3. My understanding most of the die offs occurred while they were spawning and the water was to warm in the shallows.

  4. Wow l hated those alewives. As a small child seeing and smelling the alewives all over the beaches was kind of scary.
    Alewives are much smaller than Jaws but in any lake I swam in, if a fish touched my leg, U was out of the water for awhile. Or days 😳

  5. My father, an avid fisherman, was ecstatic about the salmon. He brought home some beauties. Children being children, we doused them in ketchup before eating. I shudder just thinking about it now.

    Also, children being children, we were ecstatic about the resulting alewife-less beaches.


The Digital Research Library of Illinois History Journal™ is RATED PG-13. Please comment accordingly. Advertisements, spammers and scammers will be removed.