Linkage between fishers' foraging, market and fish stocks density: examples from some North Sea fisheries.

摘要

This study has investigated some properties of fishermen's foraging, using Levy flights theory. The case studies examined were a selection of North Sea Dutch and French vessels, for which catch and effort data were collected on a haul-by-haul basis. Foraging behaviour could reasonably be represented by a Levy flight process, characterized by an exponentiation factor ( mu ), for both fleets. The properties of fishers' foraging were further investigated for the Dutch fleet using time series analysis. Optimal foraging was found with mu =1.5, suggesting a slow recovery dynamics of the stocks being harvested. Efficient foraging led to high value per unit effort, while the knowledge of fishing grounds with high stock density is shown to increase foraging efficiency in the short-term future. Only marginal correlations could be found between mu and the other explanatory variables considered (fish prices and fishing effort)..