Hábitos alimentares e organização trófica da comunidade de peixes da Baía de Sepetiba, Rio de Janeiro, Brasil

Abstract

The aim of this study was to describe the feeding habits and trophic organization of the fish community in the Sepetiba Bay, based on the diet of the 24 most abundant fish species caught by bottom trawling between 2000 and 2001. We defined the ichthyofauna organization in trophic guild and their spatial, temporal and ontogenetic variations, behavioral aspects (trophic strategy, the trophic niche partition and feeding activity) and the feeding web organization to test the hypothesis that components of the ichthyofauna developed trophic segregation as strategy to coexist in this system. Fishes were measured (mm), weighted (g) and dissected for removing the stomachs. Stomachs contents were analyzed under optic microcopy and stereomicroscopy and the feeding items were identified at the lower possible taxonomic level. Four trophic guilds and two species with differentiated feeding were described for the studied species, indicating partition/overlapping in the use of the available resources. Spatial changes in diet were detected for most species, suggesting the high plasticity in the use of available resources. Overall, Polychaeta was the dominant feeding resource in the inner bay zone, while items from the Crustacean category dominated in the outer zone. Although indication of seasonality in the resource use have been detected, nine species change diet for the secondary items only, and some species change the main food item during one season only. Ontogenetic changes in the use of the resources were observed with Copepoda and Caprella predominating in the feeding of smaller individuals, which changed to Polychaeta and Teleostei in adult individuals. Five species (A. lineatus, C. chrysurus, D. rhombeus, H. clupeola e M. americanus) increased item diversity along the growth, while six species (C. leiarchus, C. spilopterus, P. punctatus, S. setapinnis, S. testudineus e T. lepturus) decreased the feeding spectrum. Generalist strategy was used for most species (19), however 15 from those species had a trend for specialism for a given food item. Aspistor luniscutis had the highest diversity of feeding items and width niche. Citharichthys spilopterus (diurnal) and A. lineatus (nocturnal) were the species with more defined feeding activity. Trophic guilds of the Copepoda and Polychaeta eaters had the highest trophic overlapping within the group, indicating plenty of available resources. No significant differences were found for the means trophic levels and omnivory of the species between zones, season and size classes. Connectance was influenced by removing species from the trophic web according to the degree of interaction of each species. Separation in trophic guild and the use of different trophic strategy were the mechanisms used for the ichthyofauna to coexist in the Sepetiba Bay.