Aquatic invertebrates disponibility for bentophagous fishes in two streams at the Iguaçu River basin, state of Paraná, Brazil

Abstract

Analyzing aquatic organisms present in fish stomachs is a good way to determine their availability in the environment. This paper aims to determine aquatic organism availability (especially benthos) for bentophagous fishes and to analyze spatial, temporal and ontogenetic changes in their diets. Samples were monthly taken from March 2000 to February 2001, through electrofishing, in two streams of the Iguaçu River. The stomachs were analyzed (329 units) and the results expressed through volumetric method. The diet was composed of benthic invertebrates, especially insects from several orders, being Ephemeroptera (3 families), diptera (11 families) and Trichoptera (9 families) the most consumed ones. Therefore, these groups were the most available for fish feeding. The Spearman rank correlation results were highly significant, showing high spatial, temporal and ontogenetic similarity. The high aquatic resources availability may explain the genus Trichomycterus (Siluriformes, Trichomyspteridae) abundance in the streams.