The rio Santo Antônio is a perennial lowland stream in the Brazilian semi-arid region, and is the main tributary of the upper rio Paraguaçu, an important drainage of the Chapada Diamantina. The temporal variation of the fish composition and abundance in a stretch of the middle course of the river was evaluated. Sampling was carried out monthly between August 1998 and July 1999, using standardized gear and techniques. Data on water and air temperature, water transparency, maximum and mean depth, width and area of the channel, and flow were recorded on each fish sampling occasion. Univariate and multivariate statistical analyses were employed in order to detect significant temporal differences in environmental parameters and fish abundance. Temperature, transparency and channel depth drove opposite tendencies between the dry and rainy months. The fish community richness (32) and composition did not change between these periods, but large fish caught with gillnets were more abundant in the rainy months. We conclude that the undramatic disturbance in the hydrological stream conditions between the dry and rainy periods led to weak responses of the fish assemblage. Long-term monitoring would be necessary, however, to assess the real persistence of the fish community structure in this perennial stream.
Chapada Diamantina; Ichthyofauna; Richness; Seasonality
