INFLUENCE OF ESTABLISHING MARINE RESERVES ON FISH POPULATIONS - THE CASE OF MAYOTTE ISLAND (WESTERN INDIAN-OCEAN)

This study investigates the effects of establishment of a marine reser ve on the coral reef fish communities at Mayotte Island, Western India n Ocean, after three years of protection. Both total species richness and global abundance did not differ significantly between protected an d non-protected areas. Nevertheless, there were significant difference s for numerous families and species. Most of the big carnivorous fishe s (Serranidae, Lutjanidae, Lethrinidae) were more diverse and more abu ndant in the marine reserve. Conversely, other fishes, mainly in the f amilies Pomacentridae, Scaridae and Acanthuridae, presented the opposi te pattern. The mean biomass of commercial fish species was significan tly higher in the reserve (202 g.m(-2)) than in non-protected areas (7 9 g.m(-2)). This pattern was also evident for carnivorous fishes, such as Epinephelus microdon, and semi-pelagic fishes, such as Caesionidae . In contrast, other commercial species, such as Scarus caudovittatus and Acanthurus nigricauda had higher biomass in non-protected areas. D espite this apparent contradiction, our results seem to be linked with the marine reserve protection. Cessation of fishing activities in the reserve may have caused increases in diversity, abundance and biomass of large carnivores. The decrease in the number of these fishes in no n-protected areas due to fishing may favour development of other popul ations, dominated by potential prey for carnivorous fishes.