Feeding Habits of the Green Jack (Caranx caballus Günther, 1868) on the Coast of Manzanillo, Colima, México

To increase the knowledge on the biology and the ecology of Caranx caballus (green jack), a dietary analysis was carried out. Stomachs of 271 specimens from the commercial catches of the artisanal fishery along the coasts of Manzanillo, Colima, Mexico from December 2000 to December 2001 were analyzed. Prey items in the stomach contents were identified, counted and weighed, the percentage frequency of occurrence, percentage by number and percentage by weight were calculated. We also determined indices of relative importance, diversity of trophic spectra and feeding. Forty two dietary components from five taxa were apparent: fishes, crustaceans, mollusks, cnidarians and chaetognaths. Percentage weight and volume did not vary throughout the year, and showed a distinct preference for fishes, whereas the numeric index showed a preference for crustaceans followed by fishes, chaetognaths and cnidarians. There was no difference between the diets of females and males. Feeding between green jack size groups changed with development: in terms of weight percentage, small fish fed on crustaceans, medium and large jacks fed on fishes, crustaceans and cnidarians.