Resumen de Longfin Mako Shark, Isurus paucus, in the Eastern Tropical Pacific: First Evidence of Trophic Ontogeny Based on the Isotopic Analysis of Long-term Tissues

Colombo Estupiñán-Montaño, Antonio Delgado Huertas

• The ontogeny of pelagic species is difficult to study due to their migratory patterns and the inaccessibility of their habitats, leaving a large part of their life history little understood. The aim of this work is to investigate the trophic ontogeny of an individual of Isurus paucus based on isotopic analysis of long-term tissue (vertebra and muscle). Nine samples (taken from eight vertebral collagen and one muscle) were analysed, giving δ13C values between –17.8‰ and –14.6‰, indicating use of both coastal and oceanic zones. The δ13C and δ15N values suggest that this individual of I. paucus was a secondary-third level predator (trophic position: 3.5–5.7]), with a broad isotopic niche (SEAC = 3.97‰2). The isotopic values obtained suggest that I. paucus give birth in coastal waters and then migrate towards oceanic zones, while the level of isotopic enrichment could be an indicator of the food sources and trophic level of the mother.