Resumen del producto

The feeding habitats of pelagic predators have been poorly studied mainly due to the complexity of the ecosystem where they inhabit. Using stomach content analysis, stable isotope analysis, and compoundspecific stable isotope analysis of amino acids we provide the first insight to the trophic habitats of juvenile silky sharks and dolphinfish in the Mexican Central Pacific. We analysed a total of 269 stomachs from juvenile and neonate silky sharks and 89 stomachs from dolphinfish from which 105 and 46 presented food items respectively. We found differences in the species composition among the diets of both predators. Using stable isotope analysis, we found differences in the isotopic niches for juvenile and neonate silky sharks and dolphinfish. Compound-specific stable isotope analysis of amino acids showed differences in the d15N values of the source amino acids in neonate sharks, while this values were similar among juvenile sharks and dolphinfish. Juvenile dolphinfish are considered as residents of the Mexican Central Pacific so their isotopic values represent the isoscape of that area. Furthermore, the d15N values of the source amino acids between juvenile dolphinfish and juvenile sharks were similar, that could show that juvenile silky sharks do not go into migrations and stay feeding on the same area for long periods up to three years according to the length of individuals analyzed. Even though we found differences in the d15N values of the source amino acids of neonate sharks they may behave in a similar way to the juvenile sharks and the observed differences are result of the isotopic signature related to maternal transfer.

Palabras clave: Stable isotope; Silky Shark; Dolphinfish; stomach content

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