
Adult coho salmon, captured during springtime surveys. Their bright color makes it obvious why they are also called silver salmon. Photo by Mike Albano.
Adult coho salmon, captured during springtime surveys. Their bright color makes it obvious why they are also called silver salmon. Photo by Mike Albano.
English names for Pacific salmon are relatively modern in the context of history. When Lewis and Clark made their historic journey in 1805, they were among the first English speakers to interact with the Pacific salmon species that are native to North America. From their writings, we know they encountered fish species in the Columbia River Basin that they called “red charr,” likely referring to sockeye salmon, “white salmon-trout,” possibly describing coho salmon’s silvery hue or white gum line, and simply “salmon,” which was probably the Chinook salmon. It’s unclear if they ever encountered pink or chum salmon during their expedition.
In modern English usage, each species of Pacific salmon is known by multiple common names, depending on the region and species. If you were to go fishing in Lake Michigan, you might encounter two well-known species: the Chinook (or king) salmon and the coho (or silver) salmon. But how did these species, which Lewis and Clark did not even encounter until they were near the end of their journey west, end up in the Great Lakes? Join me as we dive into how these Pacific salmon were introduced to the Great Lakes and what their life is like here in the Midwest.
Coho salmon were introduced to Lake Michigan in 1966 as part of an effort to control the population of an invasive fish species called the alewife (Alosa pseudoharengus). It is possible that this small species of herring was already present in Lake Ontario, but it was only able to access the other Great Lakes after the completed Welland Canal allowed them to access Lake Erie, bypassing Niagara Falls by the very route built to allow barges to do the same thing. The alewives might have run into trouble once they encountered lake trout, but lake trout populations were declining thanks to overfishing combined with the invasion of the sea lamprey. The lack of predators allowed alewife numbers to explode, beginning a pattern where the growing population would deplete food resources, leading to mass die-offs, with the survivors suddenly finding more food available, and the cycle would repeat. The large die-offs resulted in masses of dead fish washing up in windrows along the beaches of Lake Michigan. These piles of dead fish rotting on the lakeshore, sometimes several feet deep, were an aesthetic concern that also posed environmental and health issues for local communities.
Coho salmon, initially stocked by the state of Michigan, had some success as predators of the alewife. Their voracious appetite for small silvery fish provided pressure on the alewife population, and they also became an important game fish for recreational anglers. In addition to alewives, coho salmon consume other small fish such as smelt, an invasive species also abundant in the Great Lakes. This diet leads to rapid growth, like what these salmon would experience in their original oceanic habitat, and their predatory role helps maintain a balanced ecosystem. However, the ecosystem of the Great Lakes is complex, with new and established invasive species affecting food availability for many species, including coho salmon.
Some natural reproduction is occurring in streams that feed into Lake Michigan, but the continued presence of coho salmon is ensured by hatcheries in the surrounding states. These hatcheries collect eggs, rear the young fish, and release them into the tributary streams or directly into Lake Michigan harbors to ensure the continued presence of the salmon population. In Illinois, this work is done by the employees at the Jake Wolf Memorial Fish Hatchery, operated by the Illinois Department of Natural Resources Division of Fisheries and supported by anglers through fishing license purchases and the cooperative work of the Great Lakes Fishery Commission.
What does life look like for a coho salmon? The life cycle of coho salmon is an intricate journey filled with remarkable changes, survival challenges, and contributions to the ecosystem. In their native habitat, coho salmon are born in freshwater streams, where they go through several stages before migrating to the vast waters of the ocean, where they grow to adulthood, eventually returning to their natal streams to spawn. Here in the Midwest, the Great Lakes provide the habitat for the otherwise oceanic life stages, and hatcheries provide additional support for large numbers of these salmon in the early life stages.
Coho salmon have become an integral part of the Great Lakes ecosystem, playing a vital role in controlling invasive species while providing exceptional recreational fishing opportunities. Their life cycle, from spawning in freshwater streams to maturing in the vast waters of the Great Lakes, is a fascinating journey that continues to captivate anglers and environmentalists alike. Through ongoing management and conservation efforts, and continued support from advocacy groups, coho salmon will remain a valued species in the region’s aquatic landscape for years to come, providing economic value and maintaining the ecological balance of one of the world’s largest freshwater ecosystems.
Kayleigh Smith grew up in Alaska and the first fish she ever caught was a coho salmon. As much as she loves fish, her true passion is helping people learn about them, and she can be found leading tours and getting stoked about salmonids at Jake Wolf Memorial Fish Hatchery in Topeka. Jake Wolf grows all the coho salmon stocked by Illinois, and has a visitors center that is open every day of the year from 8:30 a.m.-3:30 p.m. If you’d like to get a closer look at the salmon or any of the other fish growing at Jake Wolf, behind-the-scenes tours of the hatchery are available by appointment by calling (309) 968-7531 or emailing Kayleigh at kayleigh.smith@illinois.gov.
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