Species composition and structure of marine fish communities of Mayotte Island (south-western Indian Ocean)

This first checklist of Mayotte marine fish species was conducted mostly from unpublished data. A total of 759 species belonging to 118 families and 360 genera was recorded. Regarding the species composition, and especially the relative diversity of the principal families, high similarities with other areas of the southwestern Indian Ocean region were observed. However, Mayotte communities stand out for their high diversity in several major families (Carangidae, Serranidae, Mullidae) and their high percentage of high trophic level species. This feature indicates ecosystems with complex biomass structures and high capacities of resistance against various pressures. A comparison of the theoretical species richness of the overall marine fish community of the island with regional data also indicates that the Mayotte community may be one of the most diversified within the area. The geographical location of Mayotte, in the centre of the western Indian Ocean "Coral Triangle", characterized by general currents favouring larval dispersal and inter-reef connectivity, its geological history and the stage of development of its reef structures are factors explaining this high biodiversity. Fish communities closely related to particular habitats, including non-reef habitats and deep-water environments, being largely unknown, this first work highlights the need to strengthen the prospecting effort to apprehend this exceptional biodiversity as a whole and thus promote an appropriate conservation policy.