Trophic resource partitioning among five flatfish species (Actinopterygii, Pleuronectiformes) in a tropical bay in south‐eastern Brazil

Abstract

Five species of flatfishes in a tropical bay in south‐eastern Brazil were studied to test the hypothesis that resource partitioning along the spatial and size dimensions has been used as a mechanism to enable coexistence. Three zones in the study area were defined according to environmental characteristics (inner, middle and outer). Sampling was conducted by otter trawl tows during daylight hours, between October 1998 and September 1999. Achiridae species (Achirus lineatus and Trinectes paulistanus) showed narrow niche width, indicating a specialized feeding strategy, preying on Polychaeta, and occurring mainly in the inner bay zone. Paralichthyidae (Citharichthys spilopterus and Etropus crossotus) and the Cynoglossidae (Symphurus tessellatus) showed broad niche width and a generalized feeding strategy preying on a large number of Crustacea. Symphurus tessellatus did not change diet with size‐dimension feeding on Amphipoda and Polychaeta, whereas C. spilopterus and E. crossotus shifted diet with growth. Citharichthys spilopterus fed mainly on Mysida and secondarily on shrimps, with juvenile preying on large amounts of Calanoida, whereas adults consumed large amounts of fishes. Isaeidae amphipods were a significant prey for both small and large E. crossotus, whereas Polychaeta Errantia were used mainly by large fishes. Etropus crossotus and S. tessellatus share similar feeding resources in outer bay zone preying on Isaeidae and Polychaeta Errantia. Differences in the Pleuronectiformes diet composition along with spatial and size changes in the use of the available resources contributed to allow the organisms’ coexistence in Sepetiba Bay. The high item diversity used by flatfishes indicates that the system plays an important role as a feeding ground, and that interspecific competition for food was unlikely.