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Biodiversity and health of coral reefs at pilot sites south of Toliara

  • Sunday, 26 April 2009 23:00
Gough, C., Harris, A., Humber, F. and Roy, R. - Blue Ventures Conservation Report

Executive summary

This report presents the results of coral reef ecosystem assessments conducted as part of a research partnership between Blue Ventures Conservation and WWF MWIOPO (Madagascar and Western Indian Ocean Program Office) in southwest Madagascar in December 2008. Results are presented to advise co-management strategies being developed by WWF Madagascar and local Vezo fishing communities.

  • The results of this study suggest that the coral reefs of Itampolo, Beheloke, Maromena and Befasy show serious signs of degradation likely to be a result of unsustainable exploitation of marine resources.

  • Hard coral cover overall is poor, although two reefs, Ambolafoty and Nosimbato exhibited exceptionally high levels of coral cover.

  • Fish diversity and biomass appear to be relatively high but data suggest instability of trophic structure as a result of the removal of top level carnivores, and the presence of increasing numbers of herbivores. This is likely to be a result of unsustainable biomass removal.

  • Low biomass of carnivorous fish in all survey zones indicates that these populations are in a state of serious depletion.

  • High urchin populations reflect densities and biomass levels from degraded reefs in other areas of the western Indian Ocean. This may be linked to low abundance of their main predators caused by chronic overfishing.

  • Ambohibola‚Äôs reefs were in the best health of those surveyed. The benthic composition shows greater similarity to less intensively fished or protected areas in Madagascar and the western Indian Ocean region.

    However, despite encouraging health of coral communities at these reefs, reef fish biomass and community structure on these sites are similar to levels seen on more degraded reefs in the region indicating that marine resources are suffering from similar levels of exploitation.

  • If present levels of fishing intensity continue, these reefs will have little capacity to resist or recover from future acute disturbances such as mass bleaching or severe storm damage because of their low coral cover, poor benthic structural complexity, high macro-algal cover, and abnormally low density of herbivorous fish.

  • Effective management of these reefs is likely to be critical to restoring key functional groups and maintaining ecosystem resilience and recovery potential.

  • Fisheries management through gear and catch restrictions have proven successful in restoring fish biomass and sustainability of fisheries. These should be considered a potentially useful management tool to act as an alternative or in conjunction with marine reserves and protected areas.

  • Reefs that already exhibit signs of resilience in their benthic community structure, such as the patch reefs in Ambohibola and Itampolo, should be taken into account when developing management strategies. These areas may show the most significant recovery responses if fisheries restrictions are imposed effectively.

  • Co-management of proposed marine protected areas in Itampolo, Beheloke, Maromena and Befasy by WWF and local village councils will help ensure that management plans meet with high levels of compliance by local communities.

  • Community educational programmes should be adopted in order to ensure greater understanding of reef recovery and resilience and the dynamics of coral ecosystems.

  • Community management goals should be realistic, measurable and verifiable.

  • Quantifiable achievements in conservation and fisheries management will support the long-term credibility of and adherence to management strategies, whilst the perception of short-term failures may have negative repercussions for future management policies.

Data from this research are available from WWF Madagascar for use by relevant parties. Please contact the authors
for more information.