Initial hopes for a revived Great Lakes sport fishery rode on the sleek muscular back of the coho salmon. Commonly called "silver salmon," this Pacific import has been planted in lakes Michigan and Superior annually since 1966 and is now an integral part of the lake's "put-and-take" sport fishing industry.
Mature cohos gorge themselves on alewives, smelt, and other forage fish. In Lake Michigan, cohos attain an average weight of five to six pounds but often top out at 10 pounds or more. In Lake Superior, where forage fish are less abundant, cohos average only two to four pounds.
Though smaller, coho salmon are spawning successfully in most Lake Superior tributaries and thus have developed some limited but self-sustaining populations. There is some concern that this aggressive fish might disrupt the spawning of other valued species, such as brook, brown and rainbow trout.
Coho salmon ordinarily return in their third year to the streams where they were planted to spawn and die. They reproduce naturally in many streams on the eastern side of Lake Michigan, but their general population must be sustained with hatchery-reared fish. Continual stocking has helped to improve the lake's predator-prey balance and given satisfaction to thousands of sport fishermen as well.