Assessing the effectiveness of marine reserves


Source: European Commission, Environment DG

Marine Protected Areas (MPAs) are intended to conserve marine habitats and fish populations and many prohibit fishing inside their borders. However, according to a recent study, local fishing activity can become concentrated around the edges of MPAs, which can have a significant impact on their effectiveness as fishery management tools.

MPAs are designed to protect population and breeding centres for fish. They allow adult fish and larvae to migrate beyond the MPA borders into unprotected waters. However, they can attract fishing vessels looking for increased yields around the borders. Other factors which affect fishing strategies include the distribution of fish stocks and their value, distance to port, season and weather. In combination, these factors can result in fishing activity becoming concentrated in favoured areas.

The study models the factors which influence the distribution of fishing activity around five Mediterranean MPAs, and provides important mapping data for conservation planners and resource managers. As the researchers relied on the cooperation of the boats for data, sampling varied from only 7-15 per cent of all fishing effort around Spanish MPAs, to 40-70 per cent for French MPAs and 100 per cent around Malta (where all fishing efforts must be precisely reported to a central agency). In all cases except Malta, fishing efforts concentrated heavily around the 'no-take' reserves.

The study has several implications for fisheries management and the conservation effectiveness of MPAs. It suggests that intense fishing on the borders may reduce overall catches by reducing reproduction rates of fish and restricting migration into other areas. This in turn may have a social impact by reducing the benefits of MPAs for fishing communities. The benefits may be overestimated if the patchy, localised concentration of fishing efforts suggested by this study is ignored. This is especially relevant as the EU implements a larger network of MPAs under the new Marine Strategy Framework1.

Evaluation of MPAs will need further, more detailed information of this sort. For example, compulsory centralised data in Malta greatly increased the confidence in the study results for the Maltese MPA. As spatial mapping and GIS (geographic information system) methods become more important in conservation, the study demonstrates that the mapping scale needed to plot meaningful data varies - generally, a larger scale is appropriate for larger MPAs, and it may also be related to the distance of the MPA from the fishing port. The authors suggest that standardised methods would help in assessment of MPAs.

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