Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8285
Title: Characterizing the feeding ecology of juvenile Chinook salmon on a continental scale using stable isotopes and stomach contents
Author: Eric Hertz, Marc Trudel, Richard D. Brodeur, Elizabeth A. Daly, Lisa B. Eisner, Edward V. Farley, Jeff Harding, Bruce MacFarlane, Jamal H. Moss, James M. Murphy
Publication Year: 2015
Journal: Marine Ecology Progress Series
Volume: 537
Pages: 247-263
Keywords: diet,Trophic level,salmon,stable isotope,niche

Trophic interactions within and among species vary widely across spatial scales and species ontogeny.  However, the drivers and implications of this variability are not well understood.  Juvenile Chinook salmon (Oncorhynchus tshawytscha) have a wide range, spanning from California to the Eastern Bering Sea in North America, but it is largely unknown how feeding ecology varies and changes with ontogeny across this range.  We collected juvenile Chinook salmon and zooplankton using standardized protocols in coastal marine waters across the North American range of juvenile Chinook salmon.  We used a combination of stomach contents and stable isotopes of nitrogen (δ15N) and carbon (δ13C) to characterize feeding ecology.  We found regional differences in prey utilization by juvenile Chinook salmon.  With growth and ontogeny, juvenile Chinook salmon in all regions became equilibrated with oceanic isotopic values.  There were regional differences in the δ13C values of juvenile Chinook salmon that may correspond with regional differences in primary productivity.  There were also regional differences in stable–isotope derived trophic level, and these estimates differed from those derived from stomach contents.  Dietary niche width, as indicated by stable isotopes, corresponded with the expected dietary diversity from stomach contents.  Our results show strong differences in feeding ecology of juvenile Chinook salmon are mainly influenced by growth–driven differences in body size and regional productivity.  Results from this comparison are the first to combine multiple approaches to assess the feeding ecology of a fish on a continental scale. 

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Theme: Ecosystem approach to improve management of marine resources
Foci: Provide scientific support for the implementation of ecosystem-based management
Characterize ecological interactions (e.g. predation, competition, parasitism, disease, etc.) within and among species.