Passage and Survival of Adult Snake River Sockeye Salmon within and Upstream from the Federal Columbia River Power System

Snake River sockeye salmon Oncorhynchus nerka are among the most endangered of all evolutionarily significant units (ESUs) of Pacific salmon. Reestablishment of natural returns of sockeye salmon is considered critical for maintenance and protection of the ESU and significant effort has been put forth to restore Snake River sockeye to a portion of their former range. Adult migration presents a significant challenge to recovery of this population due to the presence of multiple hydroelectric dams extending though much of the migration corridor coupled with a travel distance of over 1500 km to reach native spawning grounds. The passage survival and migration characteristics of adult Snake River sockeye originating from Sawtooth Valley between 2008 and 2014 within the Federal Columbia River Power System were evaluated. Detection efficiencies, conversion rates, migration characteristics, and correlates of survival were summarized. The relationship between timing, river environment, and migration success in individual reaches from Bonneville Dam to the Sawtooth Valley were examined to help identify causal factors influencing adult mortality.