Evaluation of the Index of Biotic Integrity in the Sorocaba River Basin (Brazil, SP) Based on Fish Communities

MARCIANO¹, F. T., CHAUDHRY¹, F. H. & RIBEIRO², M. C. L. de B.

¹ University of São Paulo, Engineering School of São Carlos, Water Resources Center and Applied Ecology, Av Trabalhador Sancarlense, n°400, CP. 292. CEP. 13560-970 - São Carlos/SP - Brazil. e-mail:nanda.marciano@bol.com.br; fazal@sc.usp.br

² Brazilian Institute of Geography and Statistics – Brasília-DF e-mail: mauro@lambert.net

ABSTRACT: Riverine habitats, such as creeks, rivers and contiguous lagoons, have special importance in tropical and sub-tropical natural systems. The Sorocaba River, in São Paulo State, Brazil, is an example of such systems, and presents an environmental mosaic constituted of distinct ecological conditions. An ichthyologycal study was conducted in seven tributaries of the Sorocaba River, comprising three different orders, so as to characterize habitats through an index of biotic integrity (IBI), thus providing relevant ecological information on the river basin. Field sampling was conducted to evaluate biological variables during dry and wet seasons in 1999-2000. Eleven variables indicating health and social levels of organization of the Fish communities were measured to obtain an IBI of the aquatic habitats under study so as to detect impacts on community structure. Thus, richness, total abundance of the species, intolerance, and trophic guilds were investigated. The health and organization variables for fish communities are the most important in formulating an IBI for 2nd, 3rd , and 4th order streams. In general, the Sorocaba river basin has altered with respect to fish community standards established in the last decade, which indicates some degree of degradation in the system.

Key-words: ichthyology, index of biotic integrity (IBI), Sorocaba River, environmental degradation.