Ecosystem indicators of marine survival in Puget Sound steelhead trout

• Published in: Progress in oceanography Vol. 188; p. 102419
• Main Authors: Sobocinski, Kathryn L., Kendall, Neala W., Greene, Correigh M., Schmidt, Michael W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-10-2020
• Subjects: Ecosystem; Forecasting; Indicators; Marine survival; Salmon; Steelhead; Steelhead; Salmon; Indicators; Forecasting; Ecosystem; Marine survival
• ISSN: 0079-6611; 1873-4472
• DOI: 10.1016/j.pocean.2020.102419

•A combination of factors with differing mechanisms explain declining survival of steelhead.•Seal abundance was the strongest predictor of steelhead marine survival (negative relationship).•Long-term salmon survival data and environmental data are necessary to understand changes to populations.•Generalized additive models are a flexible approach for identifying ecosystem indicators related to steelhead survival.
Understanding ecosystem drivers of fish stock performance is essential to improving conservation and management. We used a hypothesis-driven approach to identify potential ecosystem indicators and developed a retrospective analysis using regression models of steelhead trout marine survival in Puget Sound, an urban estuary in Washington State, USA, over a 30-year time series. Indicators related to predator abundance, the presence of hatchery Chinook salmon in the system, salinity of marine waters, and timing of cumulative river discharge explained the most variance in smolt survival. Seal abundance was the strongest predictor, showing a strong negative relationship with steelhead marine survival, indicating that predation pressure may influence marine survival. Several other predictors were supported in our models, but with much less individual explanatory power. Our results support the conclusion that a combination of factors with differing mechanisms have likely contributed to declining survival of steelhead in inland marine waters. This study emphasizes the importance of collecting long-term survival and environmental data, taking a hypothesis-based approach to understanding ecosystem drivers related to marine survival, and evaluating the mechanisms associated with survival for species with complex life histories like anadromous steelhead trout.