The Index of Biotic Integrity (IBI) has been used to assess the biological quality of flowing water systems in several areas of the United States and Western Europe, using the fish community. An adaptation of this index, which was firstly described by Karr (1981), was used for the first time in Brazil at the Paraíba do Sul river, between Barra Mansa and Barra do Piraí. This is a very important extent of this river because of the high pollution levels, mainly from National Siderurgy Company, and for being the main abstraction source of Rio de Janeiro water supply. A monthly standardised sampling programme to catch fish was carried out, from March-1995 to February-1996, at four fixed stations (Barra Mansa, Volta Redonda, Pinheiral e Barra do Piraí), all located at the mouth of small tributaries. Seines, casting nets and net trays were used for catch the fishes. Index of Biotic Integrity (IBI) was adapted by integrating 12 ecological attributes of fish communities, populations, and individual organisms to assess biological integrity based in Species Composition and Richness, Trophic Structure and Fish Abundance and Condition. Overall, water quality was classified between poor and fair and an improvement in IBI was detected between the high polluted Barra Mansa site and the least polluted Barra do Piraí site, although no significant difference was shown (p > 0,01). Seasonally, the best conditions were reached between March and August, and the worse between September and February, when more aloctone materials are brought to the river.
Paraíba do Sul river; biotic integrity; fish; pollution
