Nicho isotópico de espécies de peixes simpátricas em uma planície de inundação neotropical.

Abstract

This study investigated the energy sources and the isotopic niche of three fish species, one of them exotic from the lower Paraná River basin, and two natives from the upper Paraná river. The main carbon sources is the same to all species, the C3 macrophytes, with 84%, 78,3% e 32% to H. sp1, H. sp2 e H. sp3, respectively. Through isotopic metrics it was observed that there was isotopic niche overlap between a native species H. sp2 and exotic H. sp1, while among native species there was not. Hoplias sp1 and H. sp2 showed very similar values for the isotopic metrics and occupied the same trophic level. The native H. sp3 seems to have an ability to explore greater variety of resources, reflected in the higher values for the isotopic metrics. These results may be indicative of interspecific competition for resources between H. sp1 and H. sp2 due to isotopic niche overlap, and a strategy of expanding niche of native species H. sp3 to maintain viable population in the environment. It is believed that H. sp2 may have adopted different foraging strategies among juveniles and adults, which may minimize intraspecific competition and promote their survival and maintenance of population even with the possible competition imposed by exotic species.