Physical, biological and human-induced effects on the reef fishes of Fernando de Noronha archipelago, Brazil

Several factors have the potential to influence the distribution and composition of reef fish communities. Amongst the most important are rugosity, wave exposure, substrate cover and human activities. The present study evaluated the influence of these factors on reef fishes from sites following a gradient of human-induced effects on the Fernando de Noronha archipelago, northeast Brazil and determined their relative importance to reef fish ecology. Rugosity did not influence fish richness, but had a positive influence on number of individuals, juveniles and endemic species, whereas benthic cover did not seem to be an important determinant for any fish variable evaluated. These results suggest that availability of shelter (physical protection) is more limiting than availability of food (i.e. benthic cover). Furthermore, water flow showed somewhat low values, but even so, had negative effects on fish numbers. Recreational activities, albeit seemingly non-impacting, had a negative effect on fish abundance with the partially protected site (Atalaia) showing a similar community structure to the unrestricted site (Porto). These results suggest that human presence, even when supervised, may interfere on reef fish structure. Low-impact tourism practices are required especially in partially protected and unprotected areas.