Populations and production of fish in two small tributaries of the Parana River, Parana, Brazil

Mean biomass ((B) over bar) and production (P) of fish in two small tributaries of the Parana River (Parana, Brazil) were 61 kg ha(-1) and 48 kg ha(-1) yr(-1) in the Caracu River and 29 kg ha(-1) and 26 kg ha(-1) yr(-1) in the Agua do Rancho River, respectively. Matrix correlation analysis revealed high positive correlations of both (B) over bar and P to maximum depth and hiding places and, at a lower level of significance, to mean depth, pH and oxygen level. Lower (B) over bar and P values were found in the Agua do Rancho River, whose valley has retained a more natural character, rich canopy and scarcity of macrophytes, but also lower conductivity and nitrogen and phosphate levels than those in the Caracu River.