Abstract

Climate change, organic pollution and overfishing have led to major ecological disturbances in coral reefs, including the ‘coral-algal phase-shift’ phenomenon. Facing such ecological disturbance, ecological roles of herbivorous fish, which naturally regulate algal biomass, are becoming crucial for the future of the reefs. In the present study, we asked if the two species of herbivorous fishes commonly found in the Caribbean (Sparisoma viride and Acanthurus coeruleus) adapt their feeding patterns function to their habitat, and if spatial variations can be observed in their isotopic niche. On four study sites located in Guadeloupe, 10 to 20 individuals per species were collected. Isotopic signatures (C and N) were measured in muscles to define the isotopic niche of each fish species using the model SIBER. The main results show that isotopic signatures of fish vary spatially, suggesting different isotopic ratios of the ‘baseline’ among sites. Moreover, on each site, ellipses representing the isotopic niche of each species never overlap, indicating that the two species display independent niche. To conclude, the absence of overlap between niches of Sparisoma viride et Acanthurus coeruleus indicate an ecological complementarity between the two fish species in term of resource use and, by consequence, algal regulation.

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