Life-cycle modeling reveals high recovery potential of at-risk wild Chinook salmon via improved migrant survival
An underwater look at hundreds of shiny, silver juvenile Chinook salmon moving through McAllister Springs in western Washington state.
Salmon are vital ecologically, socially, and economically, but despite significant conservation efforts, many Chinook salmon populations are still struggling due to habitat changes and climate impacts, leaving them at risk of extinction. They need healthy reproduction in freshwater habitats and high survival rates as they migrate and grow from young fish, called smolts, to adults. Dams, other obstructions, and environmental changes hinder this migration and species survival. This research uses decades of data to determine which stream segments in the Middle Fork Salmon River are best for salmon and predict how improving survival rates could help their populations grow.
Despite having high-quality habitat, Chinook salmon in the Middle Fork Salmon River are declining because most streams can’t produce enough smolts to survive the high death rates during migration. With low numbers and high yearly variation, the risk of extinction for these salmon is high. The main cause of this high mortality is the negative impact of the Columbia and Snake River dams. Even after 40 years of recovery efforts including many miles of stream restoration, salmon are still at risk of extinction. This suggests that more drastic actions, like removing the dams, are needed to improve survival rates and boost salmon populations. Results show that restoring the Snake River migratory path is essential for improving salmon survival rates and maximizing the potential for young salmon to return to their natal habitats, measured in smolt-to-adult return rates.
Removing dams will significantly boost Chinook salmon populations in the Middle Fork Salmon River. Research predicts that increasing smolt-to-adult return rates from the current 0.74 percent to 1.8 percent would lead to population growth in all 23 stream segments in the Middle Fork Salmon River, suggesting that recovery is possible even at lower survival levels. However, salmon productivity may be lower in other parts of the Snake River, resulting in smaller population increases. Achieving smolt-to-adult return rates that meet regional goals would help rebuild these less productive salmon populations, increase their diversity and resilience, and enhance nutrient delivery to ecosystems. The analysis highlights the importance of using detailed, long-term data in ecological research and management.
The results of this analysis are important for shaping management decisions and evaluating the costs and benefits of restoring Snake River salmon. On December 14, 2023, a historic partnership was formed with Oregon, Washington, and the Nez Perce, Yakama, Warm Springs, and Umatilla Tribes to restore wild salmon, promote clean energy projects led by Tribes, and support local communities. The agreement recognized that removing the Lower Snake River dams is necessary to restore healthy fish populations and outlines federally funded actions to restore native fish and explore alternatives for transportation, irrigation, and recreation services currently provided by the dams.