Publication Date
1 October 2024
Understanding how Environmental Changes Contribute to Salmon Declines in Alaska and Canada
Image
Image Caption
Environmental drivers of Chinook salmon populations in the Yukon and Kuskokwim river basins
Image Credit
Image by Megan Feddern, NOAA Fisheries
Science
This study quantified how changes in freshwater and marine environments contributed to declines of Chinook salmon populations in the Yukon and Kuskokwim River Basins of Alaska and Canada
Impact
- Understanding what drives the population dynamics of Chinook salmon can help policymakers and communities understand what local and regional actions are most likely to support salmon recovery and food security. These could include changes in fishery management to account for smaller spawners when estimating future run sizes or targeted habitat restoration to help salmon cope with a changing climate.
- Understanding how salmon are responding to environmental changes may allow improved forecasts, helping fishing communities to better prepare for future ups and downs in salmon returns
Summary
- Chinook salmon populations have declined in the Yukon and Kuskokwim (YK) rivers over the last three decades, leading to fishery closures and profound impacts on culture and food security in rural and Indigenous communities in Alaska and Canada.
- This study asked why these populations have declined. Specifically, what changes in the environment were associated with the productivity of 26 Chinook populations across the YK region during the 1980s-2010s? To answer this, the research team analyzed biological observations and climatic data gathered from government agencies, Tribes and First Nations, and climate models.
- The team focused on research priorities and datasets identified by a group of 50 experts, including local and traditional knowledge holders, scientists, and fishery managers at a workshop in Fairbanks, whose insights and questions were summarized in an earlier paper
- Salmon were less productive when they encountered extreme ocean temperatures – either unusually warm summers or unusually cold winters – during their first year in the Bering Sea.
- Yukon River populations became much less productive as the body size of adult salmon declined. The declining size of Yukon River Chinook salmon has been a source of concern among fishers and scientists over many years. This is the first study to link declines in salmon body size with population declines, while taking the changing climate into account.
- Across the board, salmon were smaller in years when they encountered more competitors in the ocean (including pink salmon, chum salmon, and walleye pollock), which made it hard to distinguish the effects of declining body size from the effects of competition. These findings are consistent with – but do not prove – that competition at sea is an important contributing factor to both reduced body size and population declines of Yukon and Kuskokwim Chinook salmon.
- Water temperatures in mainstem rivers affected Yukon and Kuskokwim populations differently. Salmon from most Yukon populations were less productive when they encountered above-average river temperatures during the spawning migration, but Kuskokwim populations showed little effect.
- Other climatic conditions like fall floods when the salmon eggs were in the gravel and the timing of spring river ice breakup had more variable effects among populations.
Point of Contact
Erik Schoen
Institution(s)
University of Alaska Fairbanks
Funding Program Area(s)
Publication
Feddern, Megan L., Rebecca Shaftel, Erik R. Schoen, Curry J. Cunningham, Brendan M. Connors, Benjamin A. Staton, Al von Finster, Zachary Liller, Vanessa R. von Biela, and Katherine G. Howard. 2024. “Body Size And Early Marine Conditions Drive Changes In Chinook Salmon Productivity Across Northern Latitude Ecosystems”. Global Change Biology 30 (10). Wiley. doi:10.1111/gcb.17508.