ICTIOFAUNA DE UN SISTEMA FLUVIAL RECEPTOR DE AGUAS SERVIDAS: RESPUESTAS A UNA NUEVA PLANTA DE TRATAMIENTO (RIO QUILQUE, CHILE CENTRAL)

the quilque river (3rd order) receives urban wastewater discharge from a population of ca. 115,000 inhabitants and 19 industrial effluents. these residues were discharged without treatment until the end of 2002, when a wastewater treatment plant was constructed. to determine effects of wastewater and industrial effluents on the ichthyofauna, we studied water quality and fish community structure at eight stations distributed from upstream of the areas of the discharge to 300 m downstream of the effluent of the wastewater treatment plant. both water quality and the fish community showed a slight improvement five months after the treatment plant began operation. concentrations of bod5, suspended solids, nitrogen, and fecal coliforms decreased; however, the river contained a significant pollution load from upstream areas, and remnants in the sediments of the riverbed. the fish fauna is impoverished, but there appears to be evidence of a recolonization from upper reaches towards the lower zone receiving the pollution discharges. areas without fishes still exist due to high concentrations of bod5. the first species recolonizing the polluted areas are the native fishes trichomycterus areolatus and percilia irwini