The local management of migratory stocks: Implications for sustainable fisheries management

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Overfishing is widely recognized as a major impediment to the long term sustainability of seafood harvests. One strategy to prevent overfishing is the use of area-based management, which attempts to match fishing areas and protected areas to important geographic and ecological boundaries for a stock. However, a mismatch between the scale of area-based management and the life cycle of a fish stock may be unavoidable and can lead to problems such as serial depletion if the management scale is larger than the stock's movements, or intercept fisheries if the management scale is smaller than the stock's movements. This project explores the conditions that may promote or prevent the formation of an intercept fishery when the scale at which the stock is managed is smaller than the scale at which the stock migrates, breeds and feeds. A theoretical computer model was designed to evaluate implications of a mismatch between the scale of a fish stock's movements and the area-based management of that stock. The model examined a fishery with stationary harvesters, a migrating stock, and a protected spawning reserve. Observations were made of how harvesters in different areas respond to varying market regimes, recruitment patterns, and costs of harvesting in order to determine what economic and environmental conditions would promote or prevent an intercept fishery in the model. Overall, the economic conditions interplay with the environmental conditions to promote or restrain an intercept fishery. Specifically, an intercept fishery was prevented when recruitment levels were low and prices were constant, as might happen in a competitive global market. When recruitment levels were high, a variable price that was sensitive to local supplies was necessary to prevent the development of an intercept fishery. The model results emphasize that in the face of a mismatch, certain market and recruitment conditions may enhance or prevent the development of an intercept fishery. A sound understanding of biological parameters, such as recruitment levels, is critical to assess the risk of a developing an intercept fishery, and some control of the economic system surrounding fish harvests, such as prices, may be necessary to prevent an intercept fishery.