Newly published research co-authored by scientists at Simon Fraser University and the Raincoast Conservation Foundation shows juvenile coho salmon benefit from dining on the distant remains of their spawning pink and chum cousins.
While juvenile coho salmon feed directly on spawning pink and chum salmon carcasses and eggs, even coho with no direct contact with spawning pink and chum benefit from their nutrient contributions to stream ecosystems.
The new research shows that juvenile coho abundance is up to three times higher in streams with abundant pink and chum compared to streams with none.
John Reynolds, an SFU biologist, and Michelle Nelson, one of his doctoral students, have just had their paper Time-delayed subsidies: Interspecies population effects in salmon published in PLOS ONE, an international peer-reviewed journal.
The authors say their discovery underscores the importance of understanding how a fish's nutrient legacy in streams and forest ecosystems affects species close and distant to them.
The paper's lead author Nelson says: ""We found an indirect link between spawning pink and chum salmon, and juveniles of another species, coho." The paper is one chapter of her thesis.
The carcasses of dead pink and chum salmon that have spawned in freshwater fertilize stream and forest ecosystems. The food web pathway may go from carcasses to algae to stream-insects and then to coho. Even more fascinating is a pathway that may go from carcasses to forest flies to coho.
"We know this isn't just because all three species benefit from being in nutrient-rich streams," says Reynolds, SFU's Tom Buell BC Leadership Chair in Salmon Conservation. "The habitat needs of pink, chum and coho are slightly different, and even taking habitats into account, the effects of coho dining on nutrients enriched by pink and chum remains are very clear."
"I hope this will highlight to fisheries decision-makers the ecological benefits of robust populations of spawning salmon," says Nelson. "Pink and chum salmon have less commercial and recreational value than coho. But their crucial contribution to stream ecosystems may benefit the health of coho populations."
Reynolds adds: "These findings are relevant to many people, considering the strong interest and connection many have with salmon. It also speaks directly to the federal Department of Fisheries and Oceans' commitment to incorporate a better understanding of salmon-ecosystem interactions into fisheries management to conserve and restore salmon abundance in our region."
The research was conducted in collaboration with the Raincoast Conservation Foundation and the local Heiltsuk First Nation.
Michelle Nelson spent five field seasons in the Great Bear Rainforest visiting more than 25 streams to conduct her research. Dogged by constant rain, Nelson could only access the streams, which were in almost pristine wilderness, by boat. Wolves, black bears and bald eagles were her constant companions.
She captured and measured juvenile coho salmon, and matched them to data from a long-term study by Reynolds and his students studying chum and pink salmon, including about 50 variables representing habitat characteristics.
Nelson expects to finish her doctorate in conservation biology studying salmon-ecosystem interactions under Reynolds' supervision in July.
Nelson regularly writes magazine and newspaper articles about food, travel and urban life in the context of conservation. Douglas and McIntyre will publish her first book, on urban homesteading and conservation, next spring.
She was formerly involved in sea lice/salmon research with Alexandra Morton, an independent biologist and SFU honorary degree recipient, and she teaches undergraduate field courses in ecology.
John Reynolds heads up a large team studying aquatic conservation and ecology, focusing on issues related to salmon conservation.
John Reynolds, 778.782.5610, 604.786.0790 (cell), Reynolds@sfu.ca, Twitter: @JohnReynoldsSFU
Michelle Nelson (Bowen Island resident), 604.220.0214, firstname.lastname@example.org
Carol Thorbes, PAMR, 778.782.3035, email@example.com
The Tom Buell Foundation, the B.C. Leading Endowment Fund and the Pacific Salmon Foundation support Reynolds' research chair.
He has held a variety of scientific advisory positions, including with the B.C. Pacific Salmon Forum and the Cohen Commission. He has examined issues ranging from the negative impacts of salmon farming on wild fish to declines in Fraser sockeye salmon.
Simon Fraser University is consistently ranked among Canada's top comprehensive universities and is one of the top 50 universities in the world under 50 years old. With campuses in Vancouver, Burnaby and Surrey, B.C., SFU engages actively with the community in its research and teaching, delivers almost 150 programs to more than 30,000 students, and has more than 125,000 alumni in 130 countries.
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