Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8763
Title: Early ocean distribution of juvenile Chinook salmon in an upwelling ecosystem
Author: Jason L. Hassrick, Mark J. Henderson, David D. Huff, William J. Sydeman, Megan C. Sabal, Jeffrey A. Harding, Arnold J. Ammann, Eric D. Crandall, Eric P. Bjorkstedt, John Carlos Garza, Sean A. Hayes
Publication Year: 2016
Journal: Fisheries Oceanography
Volume: 25
Issue: 2
Pages: 133-146
Keywords: California Current,Chinook salmon,juvenile Chinook salmon,migration,Pacific Ocean,upwelling,

Extreme variability in abundance of California salmon populations is often ascribed to ocean conditions, yet relatively little is known about their marine life history.  To investigate which ocean conditions influence their distribution and abundance, we surveyed juvenile Chinook salmon (Oncorhynchus tshawytscha) within the California Current (central California [37°30′N] to Newport, Oregon [44°00′N]) for a 2-week period over three summers (2010–2012).  At each station, we measured chlorophyll-a as an indicator of primary productivity; acoustic-based metrics of zooplankton density as an indicator of potential prey availability; and physical characteristics such as bottom depth, temperature and salinity.  We also measured fork lengths and collected genetic samples from each salmon that was caught.  Genetic stock identification revealed that the majority of juvenile salmon were from the Central Valley and the Klamath Basin (91–98%).  We constructed generalized logistic-linear negative binomial hurdle models and chose the best model(s) using Akaike's Information Criterion (AIC) to determine which covariates influenced the salmon presence and, at locations where salmon were present, to determine the variables that influenced their abundance.  The probability of salmon presence was highest in shallower waters with a high chlorophyll-a concentration and close to an individual's natal river.  Catch abundance was primarily influenced by year, mean fork length and proximity to natal river.  At the scale of sampling stations, presence and abundance were not related to acoustic indices of zooplankton density.  In the weeks to months after ocean entry, California's juvenile Chinook salmon population appears to be primarily constrained to coastal waters near natal river outlets.


This is a peer- reviewed journal article that describes the alongshore distribution of juvenile salmon during spring from Newport Oregon to Monterey Bay California.  

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.