Resource partitioning among juvenile snappers in a semi-arid estuary in north-eastern Brazil

Resource partitioning is important for species coexistence. Species with similar ecomorphological characters have a high potential for competition, especially when close phylogenetically. The diet and resource partitioning of four snappers (Lutjanus alexandrei, L. analis, L. jocu and L. synagris) was studied in the Tubarão River, north-eastern Brazil, between March and November 2012. Specimens were caught using a beach seine, and a total of 731 stomachs were analysed. The highest abundance of snappers was found near to vegetated habitats in the middle estuary. Crustaceans were dominant in the diet of all four species, being found in over 90% of the stomachs, followed by fish and molluscs. The species did not appear to compete for common resources, probably because there was not always spatial overlap, and differences in the proportions of consumption of items were observed. Ontogenetic comparisons of dietary compositions suggested differences among species, with changes in the diet related to changes in the mouth area as the body size increased. The changes were more evident in L. analis and L. synagris where microcrustaceans (Calanoida, Cyclopoida and Amphipoda) were dominant in the diet of the smaller size classes, and benthic crustaceans (Brachyura) and fish in the diet of larger individuals. The intra- and inter-specific differences in the dietary compositions, differences in the mouth area and feeding strategy contribute to allow the co-existence of these snappers in the study area.