Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8171
Title: Prey availability and feeding ecology of juvenile Chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon in the northern California Current ecosystem, based on stomach content and stable isotope analyses
Author: J. N. Adams, Richard D. Brodeur, Elizabeth A. Daly, Todd W. Miller
Publication Year: 2017
Journal: Marine Biology
Keywords: stable isotopes, juvenile salmon, feeding, prey selection, coastal ocean,

Juvenile Chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon and their prey were collected in the northern California Current ecosystem from a small-scale grid of stations off Willapa Bay, Washington (bounded by 47.7346.60°N and 124.25124.44°W) during a weeklong period (9-15 June 2010). Herring and Nordic trawls were deployed to capture juvenile salmon and to quantify the catch per unit effort (CPUE) of the salmonid prey field. Juvenile salmon stomach contents were quantified and diet compositions were compared to the CPUE. Stable carbon and nitrogen isotopic values (´13C & ´15N) of salmon prey and of salmon muscle tissues were measured and used in a Bayesian stable-isotope mixing model (SIAR) to test whether stable isotope values were a good predictor of stomach contents. The herring trawl caught 37 times more prey biomass than the Nordic trawl and these nets sampled different prey communities. Juvenile Chinook and coho salmon diets were not significantly different and both principally consumed Sebastes spp. and Cancer megalopae. Juvenile salmon consumed somewhat different prey items compared to both net communities, with main differences due to Sebastes spp., Cancer megalopae and Osmeridae. These results suggest that multiple nets should be used to provide a more unbiased estimate of the salmonid prey field. SIAR model results indicated that marine fishes and invertebrates constituted the largest proportional prey contributions to juvenile salmon diets. Stable isotope analysis combined with stomach content analysis can provide a more comprehensive view of the feeding ecology of juvenile Chinook and coho salmon.

Theme: Ecosystem approach to improve management of marine resources
Foci: Characterize the interaction between marine, freshwater and terrestrial ecosystem components.
Provide scientific support for the implementation of ecosystem-based management