Trophic structure of fish fauna along the longitudinal gradient of a first-order rural stream/Estrutura trófica da fauna de peixes ao longo do gradiente longitudinal de um riacho rural de primeira ordem

This study evaluated the trophic structure of the fish assemblage along the longitudinal gradient of a first-order rural stream. Fish were sampled by electrofishing technique in December 2007, September 2008 and March 2009, at three stretch of the Itiz stream. The researchers sampled 1,255 individuals relating to 18 species. The categorization of trophic guilds was based on stomach content data of 1,096 individuals, analyzed according to the volumetric method, except for four species, which were classified according to the literature. To test the hypothesis of differences in the richness, abundance and biomass of trophic guilds along the headwater-mouth gradient, it was performed non-parametric statistical analysis of the dietary data. They registered seven guilds: herbivorous, detritivorous, aquatic insectivorous, terrestrial insectivorous, invertivorous, omnivorous and piscivorous, the latter was exclusive to headwater and middle stretches. The omnivorous guild was not recorded in the headwater.