TEMPORAL PATTERNS IN A FISH ASSEMBLAGE OF A SEMIARID MANGROVE ZONE INMADAGASCAR

Gillnet sampling was conducted for a year in a tropical mangrove creek (SW Madagascar), characterized by a limited freshwater influence, a h igh turbidity and a tidal range up to 3 m. Sixty species of juvenile f ishes were caught, 44 species being of commercial interest. Catches we re dominated by Gerreidae (27% of total abundance), Teraponidae (16%), Carangidae (13%) and Sparidae (12%). The temporary resident fishes in the mangrove zone represented 50% of the species and 97% of the total abundance, the other species being rare (less than five individuals). The species richness, abundance and biomass per netting were low in t he middle of the cool season (July-August). Monthly changes in the fis h assemblage were particularly complex, with three species groups disp laying a clear seasonal pattern, some species succeeding one another i n a rather unstructured way, and three species abundant throughout the year. There was no clear structuring effect of temperature, salinity and turbidity on the fish assemblage. However, tidal, lunar and diel e ffects on the composition of the fish assemblage were evident. The spe cies overlap between the Sarodrano mangrove fauna and the adjacent cor al reef fauna is particularly weak with six species in common and show s that the mangove plays only a very limited nursery role for coral re ef species. (C) 1997 The Fisheries Society of the British Isles.