Environmental Conservation



Density dependence in marine protected populations: a review


J.L. SÁNCHEZ LIZASO a1c1, R. GOÑI a2, O. REÑONES a2, J.A. GARCÍA CHARTON a3, R. GALZIN a4, J.T. BAYLE a1, P. SÁNCHEZ JEREZ a1, A. PÉREZ RUZAFA a3 and A.A. RAMOS a1
a1 Departamento de Ciencias Ambientales, Universidad de Alicante, PO Box 99, 03080 Alicante, Spain
a2 IEO-Centro Oceanográfico de Baleares, PO Box 291, 07080 Palma de Mallorca, Spain
a3 Departamento de Ecología, Universidad de Murcia, Campus Espinardo, 30100 Murcia, Spain
a4 EPHE-URA CNRS 1453, Université de Perpignan, 66860 Perpignan Cedex, France

Abstract

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.

(Received June 30 1999)
(Accepted February 18 2000)


Key Words: marine reserves; carrying capacity; density; fishery enhancement; Mediterranean; spillover.

Correspondence:
c1 Correspondence: Dr José Luis Sánchez Lizaso Tel: +34 965 903668 Fax: +34 965 903464 e-mail: lizaso@carn.ua.es