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Feeding habits and trophic interactions of four sympatric hammerhead shark species reveal trophic niche partitioning

Esteban Galindo*, Alan Giraldo, Andrés Felipe Navia

*Corresponding author:

ABSTRACT: Knowledge of species ecological roles 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 analyse the diet and trophic relationships of four sympatric hammerhead shark species, using a combination of stomach contents 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 suggest 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 indicates mesopredator roles, whereas Sphyrna lewini subadults could be considered top predators. Our findings revealed multiple trophic interactions between hammerhead sharks and preys from different trophic levels, which could be critical for the structure and function of marine food webs.