Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1746
Title: Interannual variability in the Northern California Current food web structure: changes in energy flow pathways and the role of forage fish, euphausiids, and jellyfish
Author: J. J. Ruzicka, Richard D. Brodeur, Robert L. Emmett, J. H. Steele, J. E. Zamon, C. A. Morgan, Andrew C. Thomas, Thomas C. Wainwright
Publication Year: 2012
Journal: Progress in Oceanography
Volume: 102
Issue: 1
Pages: 19-41
Keywords: Northern California Current, food web, model, end-to-end model, interannual variability,

The Northern California Current (NCC) is a seasonally productive and open ecosystem. It is home to both a diverse endemic community and to seasonally transient species. Productivity and food web structure vary seasonally, interannually, and decadally due to variability in the rate of nutrient input via coastal upwelling, forcing by climate-scale physical processes, and the abundance of migratory species entering the system. Important community structure changes observed between years include changes in the relative abundances of large jellyfish and small pelagic fishes (anchovies, sardines); these changes occur at intermediate trophic levels that form alternate energy transfer pathways, linking lower to upper trophic levels. Annual plankton, fish, and seabird surveys provide information about variability in pelagic community composition within the NCC. From these observations, interannual variability in trophic interactions and energy flow through the NCC system was inferred within a series of independent, mass-balanced food web models. Using these models, we quantified relative changes in energy transfer efficiency from bottom to top trophic levels, and we identified the relative importance of alternate energy transfer pathways at intermediate trophic levels. Alternate scenario investigations were used to analyze system sensitivity to variability in the strength of individual trophic linkages and system-wide response to changes in upwelling strength through time. Analysis of the range of ecosystem states observed interannually and system response to alternate forcing-scenarios will improve our ability to predict NCC ecosystem response to environmental change and quantify trophic pressures acting upon individual species.

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Theme: Ecosystem Approach to Management for the California Current Large Marine Ecosystem
Foci: Characterize ecological interactions (e.g. predation, competition, parasitism, disease, etc.) within and among species to support ecosystem approach to management.
Conduct integrated ecosystem assessments that produce metrics and criteria that will improve ecosystem forecasts and predictions.