MEPS 665:159-175 (2021)  -  DOI: https://doi.org/10.3354/meps13681

ABSTRACT: Knowledge of the ecological roles of species within food webs and how their trophic interactions affect food web structure is critical to model management and conservation scenarios for species that are suffering high levels of anthropogenic pressure, such as hammerhead sharks. In this paper, we analyze the diet and trophic relationships of 4 sympatric hammerhead shark species using a combination of stomach content and stable isotope analyses. These species showed trophic similarities by sex and trophic dissimilarities by maturity stage. We found that the trophic niche of hammerhead species tends to be more similar within species than among them. This suggests that competitive interactions are more likely to occur between conspecifics than between congeneric individuals and highlights the potential different roles that these species can play within the food web structure. The intermediate to high trophic positions observed in Sphyrna corona, S. media, S. tiburo and S. lewini juveniles indicate mesopredator roles, whereas S. lewini subadults could be considered top predators. Our findings revealed multiple trophic interactions between hammerhead sharks and prey from different trophic levels, which could be critical for the structure and function of marine food webs.

KEY WORDS: Diet · Feeding ecology · Niche overlap · Trophic level · Sphyrna spp. · Stomach content analysis · Stable isotopes