Abstract
An analysis of the diet of Astyanax paranae Eigenmann, 1914 in nine streams located in the Passa-Cinco River basin (upper Paraná River system) was performed to investigate the feeding habits of this species, check for possible spatial variations in diet and to investigate the influence of riparian vegetation in the composition of the diet. Stomach contents of 243 specimens were analyzed by the methods of relative frequency of occurrence and volume, and the diet was characterized by the alimentary index (AIi). The species showed insectivorous feeding habits, with a predominance of terrestrial and aquatic insects in the diet, varying by location. In most streams, resources of allochthonous origin were the most consumed. The participation of aquatic insects and terrestrial plants were high in most streams, while terrestrial insects and invertebrates were highest in streams with a greater presence of riparian forest. The two streams located draining pasture fields were the only places were A. paranae consumed algae and macrophyte fragments. These results were corroborated by the analysis of similarity (ANOSIM): the descriptor "percentage of riparian forest" was the highest environmental influence on the diet of A. paranae. The study shows that riparian forest percentage on the stream reach determines the species diet composition, but A. paranae is also able to gather enough food resources in a variety of severely degraded environments.
Highlights
Even though this geographic region has the highest percentage of forest remnants (15%) among Corumbataí sub-basins (Valente & Vettorazzi, 2002), its riparian forests were affected by anthropogenic occupation
Stomach contents of 243 individuals of A. paranae sampled in nine streams were analyzed
Considering all the streams, the diet of A. paranae was characterized by a high consumption of terrestrial and aquatic insects
Summary
A análise da dieta de Astyanax paranae Eigenmann, 1914 em nove riachos localizados na bacia do rio Passa-Cinco, sistema do alto rio Paraná, foi realizada com o objetivo de investigar os hábitos alimentares desta espécie, verificar possíveis variações espaciais na dieta e investigar a influência da vegetação ripária na composição da dieta. Stream ecosystems are spatially heterogeneous, regarding both the diversity of habitats, water flow, depth, temperature and substrate (Frissell & Lonzarich, 1996). These factors are closely related to the vegetative composition of the interface between terrestrial and aquatic ecosystems, the riparian zone. Even though this geographic region has the highest percentage of forest remnants (15%) among Corumbataí sub-basins (Valente & Vettorazzi, 2002), its riparian forests were affected by anthropogenic occupation
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