Regional Patterns in Spring/Summer Chinook Salmon and Steelhead Juvenile Survival Relative to Smolt-to-Adult Return Rates

Salmon and steelhead populations within the Columbia River basin enter the hydropower system at different locations and therefore experience different operational and environmental conditions during their juvenile outmigration.  However, these populations share a common estuarine and oceanic environment following passage through the hydropower system.   These common versus differential experiences allow for useful comparisons of population- and life-stage-specific survival rates and the factors that may be associated with those rates.  In this presentation, we will present long-term, mark-recapture estimates of in-river survival, ocean survival, and smolt-to-adult return rates for spring/summer Chinook salmon and steelhead populations from the Yakima, John Day, and Snake rivers and examine how these survival rates vary over time, space, and with environmental factors.  Through simulation studies that characterize these patterns of variability, we will explore survival targets and environmental conditions that may be necessary to support population recovery and achieve regional population performance goals.