Trophic habitat shifts during ontogeny of the scalloped hammerhead shark Sphyrna lewini using stable isotopes analysis in vertebrae

Studying pelagic species through their ontogeny has been difficult due to their migratory behavior and the limited accessibility to their habitats. Elasmobranchs frequently exhibit diet and habitat shifts during ontogenetic development. In this sense, the analysis of the isotopic composition (delta 15N and delta 13C) in vertebrae of the hammerhead shark Sphyrna lewini allowed the analysis of these changes individually during their ontogeny in the Gulf of Tehuantepec, M & eacute;xico. The isotopic composition (delta 15N and delta 13C) along the vertebrae transversal axis in the hammerhead shark S. lewini was analyzed using an isotopic ratio mass spectrometer. Diet and habitat shifts during ontogenetic development of both sexes were inferred from the variation patterns of the isotopic composition. A downward trend in delta 15N and delta 13C values was observed as ontogenetic development progressed. This trend suggests changes in diet and habitat parallel to ontogenetic development. Females were observed to initiate this habitat change during ontogenetic development and earlier than males. The composition of delta 13C indicated that there is sexual segregation in the use of trophic habitat in the early stages of ontogeny of the hammerhead shark. The analysis of stable carbon and nitrogen isotopes in S. lewini vertebrae allowed to detect and infer shifts in feeding habits, but mainly in habitat changes, during ontogenetic development.