Relaciones tróficas entre cinco especies de peces pelágicos que cohabitan en las costas de Oaxaca, México

Abstract

Fisheries management based on an ecosystem approach is currently promoted and, to this end, knowledge of interactions between the components of pelagic ecosystem is crucial. The aim of this study was to evaluate the trophic interactions between some components of marine pelagic ecosystem off the coast of Oaxaca. The stomach contents of five species of fishes caught during fishing tournaments and commercial fishing at the coast of Oaxaca, from May 2000 to July 2002 were analyzed. We analyzed stomach contents of 645 specimens of large predatory fishes, namely Istiophorus platypterus, Coryphaena hippurus, Thunnus albacares, Euthynnus lineatus, and Carcharhinus falciformis. Mayor forage species were Portunus xantusii and Auxis thazard: all predators consumed them in greater or lesser amounts. All fish species had narrow trophic niche breadths (BA <0.3); although they eat a wide variety of food items, their feeding is dominated by a few species, categorized as specialist feeders. The niche overlap index showed biologically significant diet overlap between C. hippurus and C. falciformis (98%), which share P. xantusii as the main component of their diet; and between E. lineatus and T. albacares (71%); and I. platypterus and E. lineatus (56%), which share few crustacean items in their diets. Despite the fact that large pelagic species share the same environment, resources are partitioned in spatial or temporal ways to reduce the pressure of competition between contending species.