DIET BREADTH AND NICHE OVERLAP BETWEEN <i>Hypostomus plecostomus</i> (LINNAEUS, 1758) AND <i>Hypostomus emarginatus</i> (VALENCIENNES, 1840) (SILURIFORMES) FROM THE COARACY NUNES HYDROELECTRIC RESERVOIR IN FERREIRA GOMES, AMAPÁ-BRAZIL.

Abstract

The stomach contents of 172 individuals of Hypostomus plecostomus and 94 specimens of Hypostomus emarginatus from the Coaracy Nunes reservoir in northern Brazil were analyzed in order to evaluate the feeding ecology of the two fish species from this site. Data were collected in eight campaigns conducted every two months between May, 2010 and July, 2011, four in the dry season and four during the flood period. The analysis of the stomach contents was based on the volumetric frequency (VF%) and frequency of occurrence (FO%), combined with the feeding index (FI). Nine different dietary items were identified: detritus, plant fragments, zooplankton, arthropods, chlorophytes, bacillariophytes, cyanobacteria, dinophytes, and unidentified material. Detritus was the principal component of the diet during both seasons, with all the other items representing only complementary or accidental portions of the diets of both species. Niche breadth was low overall, but slightly greater in H. plecostomus in comparison with H. emarginatus. Niche overlap was accentuated in both seasons, which indicates that seasonality is not a major factor influencing the characteristics of the niches of these species, possibly because of the marked abundance of detritus in the study area, specifically in the impounded sector. The two species can be characterized as detritivores, which share dietary resources with no clear evidence of any negative effects of interspecific competition on the coexistence of the two populations. Keywords: feeding ecology, niche breadth, Araguarí river, Amazonia. DOI: http://dx.doi.org/10.18561/2179-5746/biotaamazonia.v3n2p116-125