Diet of Astyanax paranae (Characidae) in streams with different riparian land covers in the Passa-Cinco River basin, southeastern Brazil

Abstract

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. KEYWORDS.Feeding ecology, Characiformes, insectivorous fishes, habitat features. RESUMO. Dieta deAstyanax paranae (Characidae) em riachos com diferentes coberturas ripárias na bacia do rio Passa-Cinco, sudeste do Brasil. 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. Foram analisados 243 estômagos através dos métodos de frequência relativa de ocorrência e volumétrico, e a dieta caracterizada através do índice alimentar (AIi). A espécie apresentou hábito alimentar insetívoro, com o predomínio de insetos terrestres e aquáticos na dieta, variando de acordo com o local. Na maioria dos riachos, os recursos mais consumidos foram os de origem alóctone. A participação de insetos aquáticos e vegetais terrestres foram elevadas na maioria dos riachos, enquanto que insetos e invertebrados terrestres apresentaram maior contribuição nos riachos com maior presença de floresta ripária. Os dois riachos drenando áreas de pastagens foram os únicos locais onde A. paranae consumiu algas e fragmentos de macrófitas. Esses resultados são corroborados pela análise de similaridade (ANOSIM), onde o descritor ambiental "porcentagem de floresta ripária" foi aquele de maior influencia na dieta de A. paranae. O estudo mostra que a porcentagem de floresta na zona ripária define a composição da dieta da espécie naquel...

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