Effect of hydraulics, bed load grain size and water factors on habitat and abundance of Narapa bonettoi Righi & Varela, 1983 of the Upper Parana River, Brazil

A cross-section of the upper Parana was studied in order to evaluate which hydraulic, sedimentary and water variables influenced on the spatial-temporal distribution and abundance of the Narapa bonettoi Righi & Varela, 1983 population, From June 1993 to February 1995, data on discharge, channel morphology, flow velocity, sediment suspended concentration and depth, water variables and benthic community were obtained. Data were analyzed by principal component analysis-PCA. The highest density of N. bonettoi occurred at the site with coarser sediments and stable bottom morphology. The lowest density was recorded at the site that presented less stable channel morphology. Temporal variation is controlled by hydrological regime and N. bonettoi cycle life whereas spatial distribution is tightly associated with channel stability.