Hatcheries and the Extirpation of Native Lake Ontario Atlantic Salmon

By Brian Morrison and Kathryn Pieman

Lake Ontario once hosted the most abundant landlocked population of Atlantic salmon in the world, with individuals reaching sizes of over 40 pounds, but they were extirpated from the lake by 1898 — a loss that happened within about 100 years of settler colonization. The usual litany of causes was cumulatively responsible for their decline, including overfishing, habitat loss, construction of dams and other barriers, and pollution. Yet, one cause has never before been suggested as also contributing to the extirpation of this once thriving population of fish. Starting in 1866, as the Atlantic salmon population declined, hatchery efforts were established to rebuild the population. To this day, these hatchery efforts are heralded as a success, but upon closer inspection, these efforts were most likely just another nail in the coffin that led to the extirpation of Atlantic salmon from this Great Lake.

The Hatchery Myth

The story goes: hatcheries are an effective tool to mitigate against population declines by increasing abundance. The simple and logically appealing premise is that hatcheries result in higher juvenile survival than the wild, and therefore, by removing high natural early mortality, more fish will be released into the system and therefore more adults will return. However, the scientific literature demonstrates that hatchery efforts usually harm the very wild populations they are supposed to support. Yet, in many cases, hatcheries continue to be seen as an acceptable and preferred solution when wild populations are failing.

The first salmon hatchery in Canada was built in Newcastle, Ontraio by Samuel Wilmot in 1866 and adopted as an official government hatchery in 1868 on his namesake creek. For 18 years, until 1883, Wilmot Hatchery cultured and stocked more than 5.5 million Atlantic salmon fry with the stated intention of restoring their numbers in Lake Ontario. Because of these efforts, Samuel

Wilmot is known as the “Father of Fish Culture” in Canada.

FLAWED ASSUMPTIONS, INCORRECT CLAIMS

Yet, upon reviewing old reports from that era, we found that Wilmot’s basic biological assumptions about Atlantic salmon were flawed, leading to incorrect claims. After hatching, Atlantic salmon need 1 to 3 stream years and 1 to 2 lake years before returning as adults to their spawning grounds, yet Wilmot claimed that adult returns were from his previous year’s juvenile stockings, which is biologically impossible. For example, adults (190 grilse, 30 multiyear lake adults) that returned in 1868 were said to be from the cohort of 15,000 salmon stocked in 1867; Wilmot stated they would “return in September, October, and November of the same year to their native stream as Grilse; and the proof that these were the result of artificial process commenced by me in the Autumn of 1866, is, to my mind and to the minds of others, conclusive and almost amounts to demonstration”. Also, there was no distinguishing mark made to hatchery fish (e.g. fin clip), and therefore, there was no way to differentiate hatchery raised fish from wild fish. Yet Wilmot claimed all adult returns to the stocked stream were due to his hatchery efforts, while ignoring concurrent increases in abundance in non-stocked watersheds indicating that wild returns had a brief resurgence. Adult returns also didn’t correspond with high stocking rates. One and a half million eggs were collected for hatchery use in 1876, the highest number ever, yet adult returns from that year

Continued on next page class were exceptionally low. Another line of evidence against the purported success of the hatchery is the poor returns of stocked Chinook salmon (Oncorhynchus tshawytscha). Between 1874 and 1881, approximately 266,000 Chinook salmon fry were stocked, yet only a handful of adults returned. The essentially nonexistent returns for stocked Chinook was likely similar to the true returns for stocked Atlantic salmon at the same time, but Chinook salmon did not have wild reproduction to mask poor hatchery performance, whereas Atlantic salmon had some strong natural returns. Wilmot also unknowingly utilized many common effects of contemporary hatchery programs, such as lack of mate choice, stocking in non-natal watersheds, homogenization (Ryman-Laikre effects), etc.

Yet none of these inconsistencies phased him. To the contrary, he was arrogant (referring to Atlantic salmon by his name, Salmo wilmoti instead of Salmo salar) and replied with rhetoric to suggestions that his activities were not working. Whether or not he knew it, his hatchery resulted in multiple forms of harm: gametes collected from wild reproducing fish reduced natural re-

Lake Ontario watersheds in Ontario (light grey) and New York (dark grey) in which Atlantic Salmon were known/purported to have historically occurred. Quaternary watersheds are highlighted for reference, but do not reflect distribution within a watershed (eg., Salmon would have only utilized habitat below waterfalls on tributaries such as the Credit River, ON and Salmon River, NY). Source of watershed mapping: Ontario Ministry of Natural Resources and Forestry and United States Department of Agriculture.

Blind Faith In Techical Solutions

production; eggs transferred out of the basin to other regions reduced total young available for the next generation (Atlantic salmon were stocked outside their endemic range in the Ottawa River watershed and the Saugeen River, Lake Huron, and were sold as gametes to various states); populations were mixed across streams which ignored the local adaptation of runs; and the release of millions of hatcheryreared fish likely resulted in negative genetic effects and loss of fitness.

This is a common story about the fallacy of untested assumptions, blind faith in technological solutions, the lack of an evidence-based initiative that has continued though history, and most importantly, how the ecological template that supports these fish cannot be separated from the fish themselves if the populations are going to be self-sustaining. The hubris of hatcheries, and the strong personalities of managers and entrenched agency practices that prioritize economic goals, continue to distract the public and fisheries officials from the underlying problems while diverting critical resources away from core solutions about the best methods for population stabilization and recovery of wild fish. Though Atlantic salmon would likely have become extirpated without hatcheries due to dams, harvest, deforestation, and pollution, this example of fisheries management is not a great Canadian success story as it is commonly claimed to be. Our full paper is available here:

“The role of hatcheries in the decline of Lake Ontario Atlantic salmon”, https://cdnsciencepub.com/doi/full/10.1 139/cjfas-2021-0253

Brian Morrison is a free-lance fisheries biologist previously working at several Conservation Authorities in Ontario since 2001 in a range of roles and capacities, and has had the fortune to study naturalized and wild salmonids across the Great Lakes.

Kathryn Pieman earned a BSc and a MSc from the University of Guelph and a PhD from UCLA. Kathyrn feels fortunate to have traveled to many cool places during academic work, from Hawaii to British Columbia, Alaska to Mexico, the Bahamas to Puerto Rico, and Australia to Denmark and Iceland, studying many aspects of behavioural ecology in fishes and birds. Kathryn is currently free-lancing in photography, videography, and science communication (https://www.youtube.com/c/NatureTidbits/videos).