Impacts of a regulatory boundary on effort distributions in the Northwest Atlantic Fisheries Organization 4X and 5Z groundfish fisheries
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Date
2020-08
Authors
Enright, Daniel
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Abstract
Effort distributions in commercial fisheries have previously been found to follow an ideal free distribution. I studied the distribution of fishing vessels in various clusters of trawling effort in the Northwest Atlantic Fisheries Organization (NAFO) Divisions 4X and 5Z, consisting of the Scotian Shelf and Georges Bank, to determine if effort distributions across a regulatory boundary follow the predictions of an ideal free distribution. First, a generalized linear mixed model was used to study the effects that impact value per unit effort (VPUE) in this fishery. Year, vessel length overall, and area fished were the fixed effects with an impact on VPUE with vessel ID and trip ID as the random effects of the model. Year coefficients often corresponded to estimated biomass for the corresponding year. VPUE tended to be higher along the boundary in 5Z. The next step used standardized value to generate isodars, equations that represent a line of equal fitness between areas, that predicted the distribution of effort among the different areas. Focusing on isodars involving areas across the 4X-5Z boundary and isodars involving the areas directly bordering the boundary allows for direct interpretation of the question of whether isodars are maintained across the regulatory boundary. Isodars were able to predict effort near the boundary and across the boundary in most situations. These findings support the overall hypothesis that effort distribution around a regulatory boundary resembles an ideal free distribution. However, the inaccuracy of predicted effort in areas of high density emphasizes the need to further study areas where the assumptions of ideal free distributions are not met.
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Keywords
Biology, Ecology, Fisheries, Effort distribution