Using a stage structured population dynamics model to determine key environmental and fishery-related drivers of AYK Chinook salmon survival

Project Description

Dramatic recent declines in the productivity of many populations of the Western Alaska Chinook salmon (Oncorhynchus tshawytscha) stock complex have jeopardized commercial, subsistence, and recreational fishing opportunities for United States and Canadian stakeholders. Similarly, rapid and broad scale global climate change may be outpacing the adaptive potential of Alaska Chinook populations, potentially influencing their future viability. However, it yet remains unclear what combination of the simultaneously occurring natural and anthropogenic factors are driving variation in Chinook salmon survival over time. Moreover, it is unknown which stages of the complex Chinook lifecycle are most sensitive to environmental change. We propose to address these fundamental knowledge gaps by tailoring and applying a pre-existing life stage-structured statistical population dynamics model to evaluate the direction and magnitude of influence that a range of hypothesized environmental factors have on realized survival for Chinook salmon populations in Western Alaska. Estimation of the influence of each environmental covariate will be informed by available adult abundance, juvenile abundance, and age composition data. Our proposed approach has three key benefits relative to alternative analytical methods. First, we will use a statistical model that will estimate the relationships between survival and environmental covariates directly from the available data, rather than a priori specifying relationships defined for other systems, pulled from the literature, or from laboratory experimentation. Second, this would be the first attempt, to our knowledge, to simultaneously evaluate both natural and anthropogenic stressors in a common estimation framework, using available juvenile and adult abundance data as the arbitrator. Third, estimated values for coefficients describing the influence of environmental factors on survival may be used to forecast future abundance trends under alternative climate and management scenarios. Taken together, we are confident that this approach will be greatly beneficial in illuminating the key freshwater, marine, and fishery factors most associated with Chinook survival in Western Alaska.