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sh. the abi iron tal gral reserve. All of these results support the hypothesis that the exportation of adult fish from Tabarca Marine Reserve occurs, and this process may influence the surrounding fished areas. resou bts ab ly et a ve also gears rounding MPAs is also controversial (Willis et al., 2003; Hilborn et al., 2004; Sale et al., 2005). A number of studies have explored the effect of the cessation of fishing within MPAs and in general, abundance, biomass and mean size of exploited fish populations are higher within protected areas than in nearby non-reserve areas (see Halpern, 2003 for review). However, to be useful as fisheries management tools, MPAs need to affect outside fished areas in a positive manner (Russ, 2002; Gell individual species biomass is important but not sufficient from an ecosystem-based perspective, being necessary to study the changes in the fish assemblage structure to evaluate precisely the recovery effects of protection. Decreasing gradients of fish bio-mass across MPA boundaries were observed in a number of studies in tropical and temperate regions, using underwater visual censu