Food habits of sailfish Istiophorus platypterus off Mazatlán, Sinaloa, Mexico

We analyzed the stomach contents of 533 sailfish taken between August 2002 and August 2003 by the sport fishing fleet off the coast of Mazatlán, Sinaloa, Mexico. A total of 62 different prey taxa was classified, 53 were identified by species, and according to index of relative importance, the most important prey species were Dosidicus gigas (d'Orbigny, 1835) (65%), Argonauta spp. (26%), Balistes polylepis (Steindachner, 1876) (6%), and Auxis spp. (1%). In spite of the apparent high prey diversity, the trophic niche breadth (Levin's index = 0.02) suggests that sailfish close to Mazatlán are specialist predators, feeding mainly on cephalopods (D. gigas and Argonauta spp.). In general, dietary overlap values between size classes ranged from moderate to high and were more evident between sizes of 99.5-119.4 cm than 179.5-199.4 cm postorbital length. There was also a high trophic overlap by sex.