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Abstract:
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A long-held view of the development of fisheries is that they initially exploit more abundant, more easily caught species, and switch over time to increasingly less abundant, less easily caught species. Moreover, it is argued that the rate at which less easily caught species are substituted for more easily caught species is accelerated in open access fisheries.
This paper addresses the question: what is the effect of fisheries management and access rules on the biodiversity of the fishery? It considers the connection between the diversity of catch in a multi-species fishery and the productivity of the fishery under different access regimes. A modified Gordon-Schaefer model is used to analyse the importance of the level of diversity in a fishery in open access and profit maximising regimes. The modified model, which includes both environmental and bioeconomic variables, is fitted to data from a gillnet fishery in Lake Malawi.
The author draws the following inferences:
- the bioeconomic diversity measure used in this paper captures the effect of a change both in the relative abundance of marketed species, and in the relative prices of those species
- there is less of an efficiency cost to the persistence of traditional open access regimes in this case, and less of an incentive to simplify the fishery
- while it is clear that year on year fluctuations in catches of particular species are indeed driven by environmental conditions, the targeting of species has historically had a significant impact on the relative abundance of those species. |