Understanding the biology of fishery resources is a basic tool in order to define their adequate administration. For this reason, trophic ecology studies provide important information about the spatio-temporal distribution of fish populations and their preys. Using passive fishing tackles such as longline and gillnets, 373 specimens of the gafftopsail sea catfish Bagre marinus were caught, from which, 252 stomachs were analyzed. Forty-one food items were identified and classified in different groups of which fish remains, the fish Anchoa sp, peneid crustaceans, the fish Cathorops mapale, fish eggs and vegetal material were the most frequent ones. The diet analysis indicates that it is an omnivore species. The feeding habits of this ariid, respond to an estuarine gradient in direction south-north, with significant differences between seasons and no significant overlapping between sites. To the north, the peneids crustaceans preys are dominant in the diets, apparently due to high salinities of this zone that favor their abundance, while the south zone, characterized by large extensions of mangroves, is apparently an adequate area for a wider spectrum of marine and estuarine preys, particularly fish.