SPATIAL PATTERN OF SIZE DISTRIBUTION OF 4 FISH SPECIES ON REUNION CORAL-REEF FLATS

A comparative study of the size distribution of four fish species was performed on three geomorphological zones (back reef, inner reef flat and outer reef flat) on two comparable fringing reef areas (disturbed and non-disturbed) of Reunion Island, S.W. Indian Ocean. The species c hosen Chaetodon trifasciatus, Dascyllus aruanus, Stethojulis albovitta ta and Ctenochaetus striatus were selected both for their abundance an d their diverse diets. The method used is based on the estimation of f ish size directly underwater by comparison to a graduated table, i.e. photographs of the species for which different size-classes were previ ously determined. For the two areas, the size of fishes increases from the back reef zone to the outer reef flat, except for D. aruanus whic h is not present in sufficient numbers on the outer reef flat to allow a statistical analysis. This suggests the existence of a nursery zone in the back reef from which these species might colonize the reef fla t. On the back reef zone and the inner reef flat, there is a significa nt difference in the size distribution of fishes between the disturbed and non-disturbed areas, except for S. albovittata. The number of juv eniles is significantly lower in the disturbed area, probably due to e nvironmental perturbations.