Pacific Salmon: The "King" Species of the Great Lakes

Located in the upper region of North America, the Great Lakes are home to an infinite amount of native and invasive species. While the formation of the Great Lakes occurred naturally around 3,000 years ago, humans have disturbed the ecosystems within the Great Lakes throughout time. Two of the most impactful invasive species that were artificially introduced into the Great Lakes, are the Coho and Chinook Salmon. Considering that a “build-it-yourself approach to ecosystem management” (Egan, 81) was normalized in the 1960s, the time period that these Pacific Salmon were released into the Great Lakes, humans had an unwavering desire to alter ecosystems for economic and personal gain.  

Unlike many species native to the Great Lakes, including lake trout, whitefish, herring, and perch, “the salmon weren’t put there to feed people,” said Great Lakes fishery historian Kristin M. Szylvian, “as much as to amuse them” (Egan, 77). Instead, the introduction of Coho and Chinook Salmon attracted tourists, sportsmen, and recreational fishers. Thus, the salmon not only affected the Great Lakes on a biological level, but also on an economic one. 

The story of the Coho and Chinook salmon is not a rare occurrence. Learning about these species is essential in understanding the detrimental effects of countless other invasive species within the Great Lakes. The following story map includes information on how these species of salmon ended up in the Great Lakes, how they have affected their surrounding ecosystems, and the efforts currently being made to manage the size of their populations

Howard Tanner, former fishery chief of the Michigan Department of Conservation, is the person responsible for the introduction of the Coho and Chinook Salmon into the Great Lakes. Believing that people “should manage [resources] to produce the greatest good for the greatest number for the longest period of time” (Egan, 649), Tanner aimed to transform the Great Lakes from a public food supply to a recreational area. In 1964, Tanner purchased around one million Coho salmon eggs from Oregon. Two years later, after breeding the Coho and Chinook Salmon in hatcheries, Tanner assisted a state legislator in dumping the salmon into the river during a public ceremony. 

Eager to increase the economic value of the Great Lakes, Tanner purposefully chose Coho and Chinook Salmon to maximize the Great Lakes’ recreational fishing potential. Not only did many recreational fishers prefer the exhilarating catch of salmon over other fish, but also Tanner knew that these species of salmon could survive in the cold waters of the Great Lakes. 

While many of the negative effects of Coho and Chinook Salmon are still unknown, these species do significantly alter the ecological, biological, and genetic composition of the Great Lakes. On an ecological level, Coho and Chinook Salmon prey on native salmon and other fish species, ultimately disturbing the trophic pyramid by increasing levels of competition and predation. The sudden influx of Coho and Chinook salmon also resulted in interbreeding between invasive and native salmon species, a reduced population size, reduced diversity in the salmon population, and inbreeding (Mills et al., 1994). Coho and chinook salmon have also been classified as ecosystem engineers since they alter habitats by disturbing sediments, fertilizing the water, and transfer nutrients throughout the Great Lakes. These behaviors result in increased levels of nitrate and phosphorus, elements that cause an excess growth of algae. These changes make it extremely difficult for other species in the Great Lakes to thrive (Janetski et al., 2019). Lastly, Coho and Chinook Salmon compete for the areas with abundant amounts of cover, increasing competition for certain habitats that native species would otherwise have priority over (Johnson, 2014).

A recent method that has been established to manage the Coho and Chinook Salmon populations in the Great Lakes is the telecoupling framework. This framework “[uses] an emerging coupled human and natural research paradigm…to investigate social-ecological interactions over distances in the Great Lakes salmonine (i.e. Coho Salmon Oncorhynchus kisutch, Chinook Salmon O. tshawytscha) fishery” (Carlson et al, 2019). The harsh reality is, however, that not much is being done to reduce the salmon population since these species bring in a great amount of money for the Great Lakes area. On an ecological level, however, other invasive species are beginning to shrink the population of Coho and Chinook Salmon.

As the health of the environment continues to decrease, salmon populations will also decrease. Nitrate and phosphorus runoff will continue to be discharged into the Great Lakes, resulting in a harsh environment for Coho and Chinook Salmon. Boats and ships will also continue to use the Great Lakes to transport goods. This leaves room for other invasive species to migrate to the Great Lakes on the outside of boats or in the ballasts. Thus, it is impossible to predict what invasive species may overpower the Coho and Chinook Salmon in the future.

Carlson, A. K., Taylor, W. W., & Liu, J. (2019). Using the telecopying framework to improve Great Lakes fisheries sustainability. Aquatic Ecosystem Health and Management, 22(3), 342-354. https://doi.org/10.1080/14634988.2019.1668660

Egan, D. (2017). Chapter 3: The world's greatest fishing hole. In The death and life of the Great Lakes (pp. 75-107). W. W. Norton & Company.

Janetski, D. J. (2012). Ecological effects of introduced Pacific salmon in Great lakes tributaries. Agriculture and Environmental Science Collection. Proquest. https://richmond.primo.exlibrisgroup.com/permalink/01URICH_INST/10lhjt5/cdi_proquest_journals_1505362777

Janetski, D. J., Chaloner, D. T., Tiegs, S. D., & Lamberti, G. A. (2009). Pacific salmon effects on stream ecosystems: A quantitative synthesis. Oecologia, 583-595. https://doi.org/10.1007/s00442-008-1249-x

Johnson, J. H. (2014). Habitat use by subyearling Chinook and coho salmon in Lake Ontario tributaries. Journal of Great Lakes Research, 40(1), 149-154. https://doi.org/10.1016/j.jglr.2013.12.006

Mills, E. L., Leach, J. H., Carlton, J. T., & Secor, C. L. (1994). Exotic species and the integrity of the Great Lakes. BioScience, 44(10), 666-676. https://doi.org/10.2307/1312510