Trophic ecology of demersal fishes from the Pacific shelf off central Mexico

Trophic interactions among ten fish species from the Pacific shelf of central Mexico were studied through the analysis of stomach contents: Cynoscion phoxocephalus Jordan and Gilbert, 1882; Diodon hystrix Linnaeus, 1758; Diodon holocanthus Linnaeus, 1758; Prionotus ruscarius Gilbert and Starks, 1904; Synodus sp., Cyclopsetta querna (Jordan and Bollman, 1890); Gymnothorax ecuatorialis (Hildebrand, 1946); Lutjanus guttatus (Steindachner, 1869); Lutjanus peru (Nichols and Murphy, 1922); and Syacium latifrons Jordan and Gilbert, 1882. Fishes were caught during 1998 by seasonal trawling at depths of 20–80 m. In total, 937 stomachs were examined and the prey grouped into 106 items. An index of relative importance of prey was estimated for each predator. The main prey were crustaceans, which were the most important prey of all predators except D. hystrix, Synodus sp., and C. querna. Mollusks were the main prey for D. hystrix and Synodus sp., while fish were the main prey of C. querna. Diodon histryx had the highest value of niche breadth followed by P. ruscarius and D. holocanthus. Niche breadth was not equal among predators, ranging from 3 to 0.3. Overlap among species was low, and the main overlap was not among species from the same genus. The same species from different years exhibited remarkable changes in diet.