Diet of fish inhabiting shallow waters close to salt marshes and mangroves was analyzed in order to evaluate how different the influence of these environments on fish feeding habits is. The six studied species, the most abundant in these areas, are mainly planctyvores, however they showed particularities in each area. In salt marshes Atherinella brasiliensis (Quoy & Gaimard, 1825) presented the largest number of food items and the lowest value of similarity regarding other species. In mangroves these attributes were presented by Anchoa januaria (Steindachner, 1879), the main species to feed on Brachyura and non-Brachyura Decapoda, and the only one in this area that includes Gammaridae in its diet. Anchoviella lepidentostole (Fowler, 1911) showed a large affinity with Anchoa lyolepis (Evermann & Marsh, 1900) in salt marshes but a large one with Opisthonema oglinum (Le Sueur, 1818) and Harengula clupeola (Cuvier, 1829) in mangroves. Similar behaviour between salt marsh and mangrove has linked H. clupeola to O. oglinum, in which diet was composed almost integrally by Diatomacea and Copepoda. The ability of fish to change their feeding habits according to the environment is well-known worldwide; here it probably results from the availability of preys, which is supposed to be different between salt marshes and mangroves. However, it was also observed that, although food items change from salt marsh to mangrove, the relationships between species remain different in both areas, helping them to be abundant in the shallow estuarine waters.
Anchoa lyolepis; Anchoviella lepidentostole; Harengula clupeola; Opisthonema oglinum; Atherinella brasiliensis
