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Ecological effects of protection in Mediterranean marine reserves

Deliverables

In view of the increased reliance on MPAs both as fisheries management and nature conservation tools, it seemed useful for managers as well as for scientists to gather the main methods available to study the effects of protection on a variety of ecological processes. For that purpose in the scope of ECOMARE a guide of methods for selected ecological studies in Mediterranean marine reserves has been produced. The aim of the guide is to present the available methods, with their advantages and limitations, and to provide references for further reading. The Guide of methods addresses the following research topics: 1. Methods for assessing biomass export from marine protected areas. 1.1. Acoustic tracking methods. 1.2. Larval otolith methods. 1.3. Genetic studies. 1.4. Ichthyoplankton sampling. 1.5. Fish visual census methods for detecting gradients of abundance and biomass across boundaries of marine protected areas. 1.6. Experimental fishing methods. 1.7. External tagging for underwater monitoring. 1.8. Identification of natural tags. 1.9. Estimating movement rates by mark-recapture methods. 2. Methods for assessing impact of human activities in marine protected areas. 2.1. Methods for studying impact on Posidonia oceanica meadows. 2.2. Methods for studying impact of trampling on rocky shallow areas. 2.3. Methods for studying impact of diver frequentation and mooring on coralligenous communities. 3. Methods for monitoring and assessing community level effects of protection: fishes-urchins-algae interactions. 3.1. Sampling techniques. 3.1.a. Population dynamics and biology of sea urchins. 3.1.b. Fish assemblages. 3.1.c. Algae. 3.2. Habitat structure and cascade effects. 3.3. Processes. 3.3.a. Grazing. 3.3.b. Predation. 3.4.c Sampling strategy and data analysis.
The concentration of multiple fishing activities in the narrow Mediterranean continental shelves has contributed to the degradation of productive and sensitive habitats such as seagrass meadows that are thought to play important physical and biological roles. Managers in the countries of the Mediterranean basin have reacted to these threats by implementing a suite of control measures including the total ban of some fishing gears such as drift-nets, the exclusion from sensitive areas of certain fishing methods (e.g., trawling within the 50 m isobath), and deployment of anti-trawling artificial reefs or creation of marine protected areas (MPAs). By 1999, some 68 MPAs had been created in the Mediterranean, of which 47 were in Spain, France and Italy. Results of studies in western Mediterranean reserves concur with those obtained in other marine regions in that the abundance of previously exploited species increases rapidly when fishing ceases. In spite of the promise of MPAs for recovery of fishery-target species, many important questions remain. Are the small existing MPAs contributing to increased recruitment of the species that are locally protected within them? Are these MPAs replenishing populations beyond their boundaries? These questions have scarcely been addressed in relation to MPAs anywhere, let alone in the Mediterranean. In the scope of the ECOMARE project, five reviews have been conducted to understand the full ecological impacts and social-economic implications of MPAs. An ultimate overall question is as to whether long-term declines can be reversed. At large scale and in general, the answer must surely be �yes�, but regrettably the large-scale options, such as protection of the whole Sea, or of entire component basins, will remain purely hypothetical. The question then is as to whether management measures at small scale can significantly serve the purpose of reversing Mediterranean degradation. The reviews typically highlight the thin scientific basis for predicting the consequences of halting fishery exploitation; part of their purpose was to identify researchable topics. Result 1 establishes the state of the art in five areas of research on the ecological effects of marine reserve protection. It consists of five review articles published in the June 2000 of the journal Environmental Conservation (Badalamenti et al. 2000; Garcia-Charton et al. 2000; Pinnegar et al. 2000; Planes et al. 2000; Sanchez Lizaso et al. 2000). The subject of the reviews can be summarized as follows: 1) The cessation or reduction of fishing in marine protected areas (MPAs) generally promotes increases of the abundance and of the mean size of exploited species. Hence, density-dependent changes in life history characteristics should occur when populations are allowed to recover in MPAs. This ECOMARE review synthesises 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 than in marine systems. 2) In connection with the increase in biomass of protected populations in MPAs, this review covers the available evidence of recruitment export from MPAs both in the Mediterranean and elsewhere. The general questions of interest are whether the increase in biomass of the protected species in a MPA has an effect on recruitment in the MPA or in neighbouring areas and if it affects competition and predation on new recruits inside the MPA. The review highlights the almost total absence of studies addressing even the most elemental questions of recruitment in the context of marine reserves. 3) The thirdd review tackles the subject of trophic cascades in marine reserves with the aim of establishing how widespread cascades are and of inferring how likely they are to affect community outcomes of MPAs. 4) Our capability to detect and predict the responses of marine communities to protection in MPAs depends on our ability to distinguish between the influence of management measures and that of natural variability. In this context, the fourth review tackles the question of the scale of the responses of populations to protection against their �normal� spatio-temporal heterogeneity. 5) Marine reserves are not only important for protecting the marine environment, but they also have substantial socio-cultural impacts about which very little is currently known. This ECOMARE review addreses these impacts and highlights the importance of not neglecting the social, cultural and economic effects of marine reserves. No single model of community participation is valid for the whole Mediterranean: the variable characteristics of coastal areas, from those of small uninhabited islands to those of cities, require different weightings to be assigned for each factor in order to achieve a durable equilibrium and realise the original objectives of a marine reserve.

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