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Concentration profiles and invertebrate fisheries management

Prince, J. and Hilborn, R. (1998) Concentration profiles and invertebrate fisheries management. In: Jamieson, G.S. and Campbell, A., (eds.) Proceedings of the North Pacific Symposium on Invertebrate Stock Assessment and Management. Can. Spec. Publ. Fish. Aquat. Sci. 125. NRC Press, Ottawa, Ontario, Canada, pp. 187-196.

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The spatial distribution of resources and the behavior of a species lead to a spatial pattern of density which has been called the concentration profile of the species. Some species aggregate and may be found almost entirely at high densities, other species space themselves much more uniformly and are usually found at low densities, and some species are found at a very wide range of densities. The interaction between the concentration profile, fishing, and management behavior leads to a number of surprising consequences. Fishermen will naturally tend to fish in the most profitable places, so that the interaction between the concentration profile of the species and the behavior of the fishermen will lead to a complex spatial pattern in abundance, profitability, and catch per unit effort (CPUE). Among the behaviors that emerge from such analysis are (i) overall CPUE will frequently decline more rapidly than abundance, (ii) CPUE will provide almost no information about abundance that can be used for management except on the smallest of spatial scales, and (iii) changes in price or costs of fishing may have significant impacts on the spatial pattern of fishing effort and the associated CPUE. We illustrate these principles in detail with examples from the Tasmanian abalone fishery on a small scale (tens of metres) and a large scale (hundreds of kilometres). Recognition of the concentration profile of the stock suggests that regulatory measures must be carefully tuned to the biology of the species. CPUE will almost certainly be a very poor measure of stock abundance, while fishery-independent surveys will provide the only reliable method of estimating stock status. Complex spatial structure, with differences in growth and mortality will mean that size limits and harvest rates should be finely tuned to the spatial structure of the stock and cannot be set appropriately over large areas. We consider alternative regulatory schemes such as quotas, seasons, size limits, and territorial fishing rights allocations in relation to concentration profiles and suggest that territorial fishing rights offer the greatest potential benefits.

Publication Type: Book Chapter
Publisher: NRC Press
Copyright: © 1998 National Research Council of Canada
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