Dissipation of Spatial Closure Benefits as a Result of Non-Compliance

D. J. Die, R. A. Watson, (1992). Mathematics and computers in simulation 33, 451-456.

Spatial closures are imposed by resource managers to prevent the operation of fishing fleets in certain areas of a stock’s distribution. In Queensland, east coast trawl closures are usually located in shallow waters to prevent fishing of prawns before they reach an optimum marketable size and migrate offshore. The success of such fishery controls should be measured by careful analysis of the benefits to fishery production, and the costs and practicality of enforcing the regulation. The potential of simulation models to investigate optimising fishery production by adjusting the starting date, length and extent of a fishing closure has been established in the Torres Straits tiger prawn fishery. It was predicted that by modifying the length and starting dates of seasonal closures that gains of up to 15% in yield-per-recruit and value-per-recruit could be achieved. By comparison, the best gains predicted by adjusting the boundaries of permanent spatial closures were less than 10% of value-per-recruit and negligible for yield-per-recruit. Enforcing fisheries regulations is expensive and especially difficult in the case of spatial closures. Most fishers are aware of this difficulty and some fish in closed areas because of the competitive advantage and the short-term benefits this practice provides. Therefore, it is important to evaluate the level of non-compliance which would dissipate the benefits gained from any closure regulations. In this paper the effect of cheating is evaluated by value-per-recruit and egg-per recruit analysis.

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