Use of fish taxocenosis as indicator of environmental degradation in the Paraiba do Sul River (Rio de Janeiro, Brazil)

An adaptation of index of biotic integrity (IBI) was performed for the first time in Brazil at the Rio Paraiba do Sul, between Barra Mansa and Barra do Pirai, a very important extent of this river because of the high pollution levels, and for being the main abstraction source of Rio de Janeiro city wafer supply. A monthly standardised sampling programme, from March-1995 to February-1996, was carried out at four sites. Seines, casting nets and net trays were used for catching fishes. IBI was obtained by integrating 12 ecological and environmental attributes of fish taxocene, populations, and individual organisms to assess biological integrity based in Species Composition, Trophic Structure and Fish Condition. Overall, water quality was classified between poor and fair and an improvement was detected between the high polluted Barra Mansa site and the less polluted Barra do Pirai site, showing the capacity of restoration of the river over this 50 km. Seasonally, the best conditions were reached from March to August, and the worse, from September to February, when most aloctone materials are brought to the river.