Salmon Life Cycle Models Illuminate Population Consequences of Disparate Survival and Behavior Between Hatchery- and Wild-Origin Fish

In past decades there has been a heavy reliance on the production of hatchery-reared fish to supplement declining population numbers of Pacific salmon. In some cases, the benefits of hatchery supplementation have been negligible despite concerted long-term stocking efforts. The management and conservation of depressed salmon populations, via hatchery practices or otherwise, can be improved by expanding our understanding of the dissimilarities between hatchery and wild salmon and how each interacts with the environment. In this study we use a stage-structured salmon life-cycle model to explore the population consequences of disparate survival and behavior between hatchery and wild-origin fall-run Chinook Salmon (Oncorhynchus tshawytscha) in the California Central Valley. We couple empirically-based statistical functions with deterministic theoretical models to identify how environmental conditions (e.g., water temperature, flow) and habitat drive the survival and abundance of both hatchery and wild salmon as they integrate across riverscapes and cross marine and freshwater ecosystem boundaries during their life cycle. Results from this study suggest that hatchery practices can lead to dissimilar interactions between hatchery and wild salmon and the environmental conditions they experience. As such, the population dynamics of fall-run Chinook Salmon in the California Central Valley are partly dependent on the composition of individuals that make up their populations. In total, this study improves out ability to conserve imperiled salmonids by identifying mechanistic linkages between the natal origin of salmon, survival and behavior, and the environment at spatiotemporal scales relevant to salmon populations and fisheries management.