Spatial dimension and exploitation dynamics of local fishing grounds by fishers targeting several flatfish species
Abstract:Patch exploitation dynamics, based on individual tow data, provided new insights into the fishing behavior of mixed fisheries. Fishing grounds were determined and their geometry quantified based on the proximity of tow positions. Tows were classified as being part of either searching, sampling, or exploitation behavior based on the intertow distance. Fishers can detect patches of flatfish on a scale of ∼25 nautical miles2. Catch rate during exploitation was 24%–36% above the catch rate while searching, and decreased at a rate of 20%·day–1. Once a patch was found, exploitation occurred until the catch rate dropped below a threshold level. The optimal giving-up catch rate was estimated based on the observed search time, catch rate decline, and range of fishing ground quality. The observed giving-up catch rate was 6%–11% higher than predicted by the marginal value theorem. The discrepancy between the observed and predicted patch leaving decision was consistent with the bias expected in an individual transferable quota (ITQ) management system. Our results provide a basis for interpreting vessel monitoring system (VMS) data and studying the interaction among fishers and between fishers and their resources at the appropriate time and spatial scale.
Document Type: Research Article
Affiliations: IMARES, Institute for Marine Resources and Ecosystem Studies, P.O. Box 68, 1970 AB IJmuiden, the Netherlands.
Publication date: June 1, 2011
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- Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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