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Density dependence in marine protected populations: a review

TitleDensity dependence in marine protected populations: a review
Publication TypeJournal Article
Year of Publication2000
AuthorsSanchez-Lizaso J-L, Pérez-Ruzafa A, Renones O, Goni R, Garcia-Charton J-A, Galzin R, Bayle J-T, Sanchez-Jerez P, Ramos A-A
JournalEnvironmental Conservation
Keywordsbiomass, boundary, Cabrera, Campello, carrying capacity, Castellamare, Columbretes, Corsica, Côte Bleue, density, ecosystem, fish abundance, fish density, fishery, fishing prohibition, France, habitat, Italy, labridae, Ligurian Sea, management, management tool, marine protected area, Medes, Mediterranean sea, mortality, movement, population, protected area, review, rocky shore, Scandola, serranidae, Sicilia, size, Spain, sparidae, spillover, Tabarca, visual census, western Mediterranean

The cessation or reduction of fishing in marine protected areas (MPAs) should promote an increase in abundance and mean size and age of previously exploited populations. Thus density-dependent changes in life-history characteristics should occur when populations are allowed to recover in MPAs. In this review, we synthesize the existing information on resource limitation in marine ecosystems, density-dependent changes in life-history traits of exploited populations and evidence for biomass export from MPAs. Most evidence for compensatory changes in biological variables has been derived from observations on populations depleted by high fishing mortality or on strong year classes, but these changes are more evident in juveniles than in adults and in freshwater rather than in marine systems. It is unclear if adults of exploited marine populations are resource limited. This may suggest that exploited populations are controlled mainly by density-independent processes, which could be a consequence of the depleted state of most exploited populations. MPAs could be a useful tool for testing these hypotheses. If we assume that resources become limiting inside MPAs, it is plausible that, if suitable habitats exist, mobile species will search for resources outside of the MPAs, leading to export of biomass to areas which are fished. However, it is not possible to establish from the available data whether this export will be a response to resource limitation inside the MPAs, the result of random movements across MPA boundaries or both. We discuss the implications of this process for the use of MPAs as fisheries management tools.

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