Size-related shifts in dietary composition of Centropomus parallelus (Perciformes: Centropomidae) in an estuarine ecosystem of the southeastern coast of Brazil

Size-related and seasonal evaluation of the dietary composition of fat snook (Centropomus parallelus Poey 1860) in the upper sector of an estuary of the southeastern coast of Brazil were carried out based on stomach analyses of specimens ranging from 40 to 170 mm standard length. Results reveal that C. parallelus is a carnivorous species feeding mainly on benthic crustaceans. Relatively high stomach replenishment suggests that this environment is an important feeding ground for fat snook juveniles. Multivariate analyses indicated that predator size effect is significantly more important than seasonal variation in determining dietary composition. Predator length was associated with increased consumption of palaemonid shrimps (Macrobrachium spp.) and grapsid crabs, and decreased foraging on tanaids (Kalliapseudes schubarti), thus showing a preference shift from smaller to larger prey. Predator length was also positively associated with an increase in the stomach repletion index. Additionally, allometric growth of both gape and head were consistently correlated with this ontogenetic dietary transition, suggesting that such changes might be related to an individual's ability to capture and consume larger, more elusive prey. The digestive tube is short and grows isometrically, which is in accordance with the carnivorous habit of this estuarine fish and its maintenance through ontogeny.

DIET of THE BLUE MARLIN (MAKAIRA NIGRICANS, LACEPEDE 1802) (PERCIFORMES: ISTIOPHORIDAE) of THE SOUTHWESTERN EQUATORIAL ATLANTIC OCEAN.

Diet composition of the blue marlin, Makaira nigricans, from the southwestern equatorial Atlantic Ocean was analyzed between October 2004 and November 2005. In the 226 stomachs of fish ranging between 100 and 311 cm lower jaw -fork length (LJFL), 44 items were identified, including 31 fishes and 13 cephalopods. Seventy stomachs were empty (23.6 %). M. nigricans fed preferentially on heavy and muscular scombrid fishes especially upon the skipjack tuna, Katsuwonus pelamis (Linnaeus, 1758), probably to sustain their high metabolism, and on a variety of other items composed mainly by epipelagic species of fish and cephalopods.