In this paper the population structure, feeding habits and reproduction of Astyanax scabripinnis Jenyns, 1842 were described, based on the analysis of fish collected monthly from October 1998 to September 1999 in a forest stream of the upper Iguaçu River basin. Length frequency distributions registered were different between males (5.4-6.7 cm) and females (6.1-8.1 cm). Significant differences of condition factor values between sexes were found, meaning different growth rates. The reproductive period occurred from October to March, as described for other characids of the same area. Terrestrial insects fragments, superior vegetables residue and aquatic insects larvae were the main food items consumed, indicating a pronounced dependence of the feeding on the allochthonous items imported from the riparian vegetation. Possible implications of physical, chemical and hydrologic seasonal variations on A. scabripinnis natural history were discussed.
Biological parameters; feeding; population structure
