An evaluation of Chinook salmon (Onchorhynchus tshawytscha) survival from Klamath-Trinity river hatcheries in their first-year at sea reveals unique response to local oceanographic conditions

Graduation Date

2014

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Fisheries, 2014

Committee Chair Name

David G. Hankin

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Humboldt State University -- Theses -- Fisheries, Survival, Mixed layer depth, California Current, Chinook salmon, Klamath River, Pacific Decadal Oscillation (PDO), El Nino, Coded Wire Tags (CWT), North Pacific Gyre Oscillation (NPGO), Akaike's Information Criteria (AIC), Logistic regression, Cape Blanco, Trinity River, Upwelling

Abstract

High interannual variability in abundance of adult Chinook salmon (Oncorhynchus tshawytscha) presents challenges to fishery managers in developing reliable predictive models of abundance. Variability in adult abundance is strongly dependent on survival during the marine life history phase, and especially during the early marine residency of juveniles. The present study evaluated 28 years of estimated first-year marine survival rates for Chinook salmon released from Klamath-Trinity River (KT) hatcheries to identify individual oceanographic and atmospheric covariates that may be related to survival, and to identify periods within that first year that most strongly affect survival. Survival rates of subyearlings released from KT hatcheries at two different times each year (fingerlings in June, "yearlings" in October) were evaluated independently. Predictive models of survival were constructed using beta-binomial logistic regression and model performances were assessed in a two-phase analysis using AICc. The predictive ability of AICc-based top models was evaluated by assessing the proportion of predicted survival rates falling within 95% parametric bootstrap prediction intervals for two out-of-sample brood years. Marine survival of KT Chinook salmon was positively related to the Pacific Decadal Oscillation (PDO), which stands in contrast to all previous work linking the PDO to marine survival of Pacific salmonids. However, KT Chinook salmon appear to respond to El Niño and La Niña conditions in kind with other Pacific salmonids. Winter preconditioning, and conditions encountered during the periods of ocean entrance and the first winter at sea were found to strongly affect survival of fingerings; conditions encountered during the first winter at sea and the following spring were found to strongly affect survival of yearlings. Mixed layer depth was consistently more related to survival of both fingerlings and yearlings than was coastal boundary upwelling. The ability of AICc-based top models to predict survival rates beyond the data used to fit models for both fingerlings and yearlings was unsatisfactory, and may not provide an adequate basis for prediction in a practical management setting. Regardless, these analyses provide important new insights concerning the most influential oceanographic factors affecting early marine survival of an important population of Chinook salmon in California.

https://scholarworks.calstate.edu/concern/theses/k643b3536

Link to Full Text

Share

 
COinS