MEPS 537:247-263 (2015)  -  DOI: https://doi.org/10.3354/meps11440

Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

Eric Hertz1,*, M. Trudel1,2, R. D. Brodeur3, E. A. Daly4,**, L. Eisner5,**, E. V. Farley Jr.5,**, J. A. Harding6,**, R. B. MacFarlane6,**, S. Mazumder1,**, J. H. Moss5,**, J. M. Murphy5,**, A. Mazumder1

1Department of Biology, University of Victoria, PO Box 3020, Station CSC, Victoria, British Columbia V8W 3N5, Canada
2Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada
3National Marine Fisheries Service, Northwest Fisheries Science Center, Hatfield Marine Science Center, 2030 S. Marine Science Drive, Newport, Oregon 97365, USA
4Cooperative Institute for Marine Resources Studies, Oregon State University, Hatfield Marine Science Center, 2030 S. Marine Science Drive, Newport, Oregon 97365, USA
5National Marine Fisheries Service, Alaska Fisheries Science Center, Auke Bay Laboratories, Ted Stevens Marine Research Institute, 17109 Point Lena Loop Road, Juneau, Alaska 99801-8626, USA
6National Oceanic and Atmospheric Administration-Fisheries, Southwest Fisheries Science Center, Santa Cruz Laboratory, 110 Shaffer Road, Santa Cruz, California 95060, USA
**Corresponding author: **Authors listed alphabetically

ABSTRACT: 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 distribution, ranging from northern California to the eastern Bering Sea in North America, but it is largely unknown how their feeding ecology varies and changes with ontogeny across this range. We collected juvenile Chinook salmon and zooplankton using standardized protocols along the coastal Northeast Pacific Ocean. Using 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 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 to regional differences in sea surface temperature. There were also regional differences in stable isotope-derived trophic level, and these estimates differed from those derived from stomach contents, possibly due to the different periods over which these metrics integrate. Dietary niche width, as indicated by stable isotopes, corresponded to the expected dietary diversity from stomach contents, combined with the isotopic variability seen in baseline values. Our results indicate strong geographic and ontogenetic differences in feeding ecology of juvenile Chinook salmon. These differences are likely influenced by a combination of ocean-entry date, ocean-entry size, ontogeny, growth rates and regional conditions.


KEY WORDS: Diet · Stable isotope · Trophic level · Turnover · Diet dependent discrimination factor · Oncorhynchus tshawytscha · Carbon · Nitrogen · Niche width · Ontogeny


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Cite this article as: Hertz E, Trudel M, Brodeur RD, Daly EA and others (2015) Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean. Mar Ecol Prog Ser 537:247-263. https://doi.org/10.3354/meps11440

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