Astyanax fasciatus as bioindicator of water pollution of Rio dos Sinos, RS, Brazil.

The effects of an increasing downriver pollution gradient on the reproductive system of Astyanax fasciatus were investigated in the Rio dos Sinos, RS. The comparison of mean oocyte diameters, gonadal indices and gonado-somatic relationships of specimens captured in polluted areas with individuals from unpolluted reference sites revealed a significant decrease of these parameters with increasing water pollution. High loads of organic and industrial sewage are considered responsible for these effects. Condition factors showed an inverse relationship, and increased significantly in down-river polluted areas. The declining gonadal indices showed that energy was allocated to somatic growth. The results of the study recommend the use of A. fasciatus in biomonitoring essays.