Toward Ecosystem-based Extraction Policies for Prince William Sound, Alaska: Integrating Conflicting Objectives and Rebuilding Pinnipeds
Abstract:Trade-offs between the benefits and the costs of marine resource extraction become increasingly conspicuous as ecological limits are approached. Unfortunately, the historical lack of trade-off accounting has led to unexpectedly adverse effects. An integrative policy-search procedure in the modeling software Ecopath with Ecosim was used to shape fisheries extraction policies for Prince William Sound, Alaska, that explicitly account for trade-offs among economic, employment, and ecological objectives, in addition to the thermodynamic constraints of the system’s food web. When economic and employment objectives were emphasized, the modeling routine reduced predators (Pacific halibut and pinnipeds) to maximize the production of prey groups whose market values and potential system biomasses promised maximum fisheries values. When ecological objectives were emphasized, the routine increased predators (orcas, halibut, porpoise, pinnipeds, lingcod, and seabirds), along with their salmon and herring prey, while decreasing gadoids (sablefish, Pacific cod, and pollock). Competition between fisheries and predators was indicated by increases in predators with decreases in fishing. A 20% increase in the biomass of pinnipeds was achieved with comparatively modest, but "smart," fisheries reductions. Commercial and overall fisheries catches consistently decreased by the end of all 20-yr simulations, indicating that 1994–1996 commercial fishing levels were unsustainable.
Document Type: Research Article
Publication date: 2004-05-01
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