Feeding patterns of two sympatric shark predators in coastal ecosystems of an oceanic island

Stomach contents and stable carbon and nitrogen isotope analyses (delta C-13 and delta N-15) were used to investigate the trophic ecology of two apex predators, tiger sharks (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas), from Reunion Island to describe their dietary habits at both the population and individual levels. In this oceanic island, the tiger and bull sharks were more piscivorous and teutophagous than noted in previous research from other localities. The delta C-13 values suggested that bull sharks depended on more neritic organic matter sources than tiger sharks, confirming a coastal habitat preference for bull sharks. Moreover, the total length of the bull shark influenced delta C-13 values, with smaller individuals being more coastal than larger individuals. All indicators suggest that there is a higher degree of similarity between individual tiger sharks compared with the more heterogeneous bull shark population, which is composed of individuals who specialize on different prey. These results suggest that the two species have different functions in these coastal habitats, and thus, they must be considered independently in terms of conservation and management.