Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1509
Title: Food web structure and trophic controls in central Puget Sound
Author: C. J. Harvey, G. D. Williams, P. S. Levin
Publication Year: 2012
Journal: Estuaries and Coasts
Volume: 35
Pages: 821-838
DOI: 10.1007/s12237-012-9483-1
Keywords: Puget Sound,ecosystem model,food webs,trophic structure,ecosystem based management,Ecopath with Ecosim

We developed a food web model of central Puget Sound to provide science-based support for ecosystem-based management and to refine our understanding of bottom-up and top-down trophic forcing. Phytoplankton accounted for a large fraction of total biomass, total throughput, and caused considerable bottom-up effects in most functional groups in a dynamic simulation fit to time series data from 1981 to 2000. Top-down control was most apparent in the case of bald eagles (Haliaeetus leucocephalus), which exhibited keystone tendencies and appeared capable of causing trophic cascades. Increasing top-down control in several predator–prey relationships improved model fits to time series data from 1981 to 2000, but not as much as introducing non-equilibrium dynamics (biomass accumulation terms) to several key vertebrates. Fishing had little effect on system dynamics. Our model appears well-suited for addressing strategic, scenario-based questions of how the community as a whole will respond to management actions.

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