Restoring the Great Lakes Fishery

Faced with a ecological disaster, various governmental agencies proposed ways to restore the Great Lakes fishery. Federal officials suggested finding some commercial application for the alewife. They hoped that by finding a market for the fish they could breathe new life into the commercial fishing industry as well as control the alewife population. The Michigan Department of Natural Resources countered these federal ideas with a much bolder proposal, to end the problem by re-establishing the predator-prey relationship in the lakes that had previously held the alewives in check.

In part this approach was made possible by the development of successful ways to limit the lamprey population. Partially successful mechanical and electrical barriers that had been set up to stop the lamprey from reaching spawning grounds were augmented in 1958 by the introduction of a highly selective, very effective chemical larvacide. This combination of tools significantly lessened the lamprey population to the point where large predator fish species could again survive in the lakes.

In 1966 the state of Michigan began to release coho salmon as its predator of choice to solve the alewife problem. Although not native to the Great Lakes, coho were efficient predators that would prosper off the alewife. Coho were easily grown in hatcheries, grew quickly in the wild, were an excellent sport fishing species, and were not believed to be capable of reproducing themselves naturally in the Great Lakes, thus giving the state a way to rid the waterways of the species if they proved a problem. Coho and other salmon species were spectacularly successful in Lake Michigan, however they did less well in Lake Superior. There the state and federal government focused on restocking the native lake trout population. This, however proved difficult. The slow-maturing trout gave the limited lamprey population several years to find their victims and even relatively low levels of water pollution often led to sterilization of the trout making it impossible for them to naturally reproduce.