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Benefits beyond boundaries: the fishery effects of marine reserves

F.R. Gell and C.M. Roberts

Reserves promote large, rapid and sustained build-up of biomass of commercially important species within their boundaries. Increases in protected populations are often rapid, frequently doubling or tripling in two to five years. Species that respond most rapidly to protection are often relatively sedentary and spend much of their life in reserves, including invertebrates. Many coral reef fish are also relatively sedentary and have benefited rapidly from protection. The key to success is matching reserve size to the scales of movements of the organisms that they are designed to protect. The overall scale of protection is as important as the size of reserve units. More than 40 theoretical and modeling studies have addressed the question of how much of the sea should be protected from fishing. Depending on the fishery and conditions being considered, they conclude that fisheries benefits require closures of between 10 and 80% of fishing grounds. Most predict maximum benefits with closures of 20–40%.