MEPS 460:155-167 (2012)  -  DOI: https://doi.org/10.3354/meps09772

Four decades of foraging history: stock-specific variation in the carbon and nitrogen stable isotope signatures of Alaskan sockeye salmon

Susan P. Johnson*, Daniel E. Schindler

University of Washington School of Aquatic and Fisheries Sciences, University of Washington, Box 355020, Seattle, Washington 98195, USA
*Email:

ABSTRACT: Broad-scale shifts in climate during the 20th century had large effects on the ecology of the North Pacific Ocean, including a substantial change in the composition of the dominant food web. Salmon production in Alaskan stocks increased with a concurrent shift of the Pacific Decadal Oscillation in 1977. Salmon production has since been persistently high through 2010, yet the biological mechanisms for this increase in production remain unclear. Carbon and nitrogen stable isotopes of sockeye salmon scales collected from 8 rivers in Bristol Bay between 1964 and 2003 were analyzed to assess whether the trophic ecology of these fish changed systematically over this period, during which there were substantial changes in oceanographic conditions. Isotope values were remarkably stable over the study despite substantial changes in salmon production and oceanographic conditions in this region. Our results also suggest river-specific patterns in the variation of stable isotopes through time; stable isotope changes were related to stock identity and showed some geographic organization. Larger salmon tended to have depleted δ15N and δ13C. Isotopic characteristics among rivers became more variable during the period of high ocean productivity (after the 1977 regime shift and before the 1989 regime shift). Some of the dominant signals of variation in stable isotope variation were related to important environmental physical processes, but they appear to have unique effects on the isotopic characteristics of stocks from different rivers, suggesting important connections between the ecology of sockeye salmon in freshwater and in the ocean.


KEY WORDS: Climate · Trophic ecology · Biocomplexity · Food web · North Pacific Ocean · Pacific Decadal Oscillation


Full text in pdf format  
Cite this article as: Johnson SP, Schindler DE (2012) Four decades of foraging history: stock-specific variation in the carbon and nitrogen stable isotope signatures of Alaskan sockeye salmon. Mar Ecol Prog Ser 460:155-167. https://doi.org/10.3354/meps09772

Export citation
Mail this link - Contents Mailing Lists - RSS
- -