Barroso, R.M., School of Biological Science, Washington State University, Pullman, WA 99164-4236, United States
Hilsdorf, A.W.S., Unit of Environmental Sciences, University of Mogi das Cruzes, P.O. Box 411, 08701-970, Mogi das Cruzes, SP, Brazil
Moreira, H.L.M., Department of Zoology and Genetics, Pelotas Federal University, P.O. Box 354, 96010-900, Pelotas, RS, Brazil
Cabello, P.H., Department of Genetics, Oswaldo Cruz Institute, Rio de Janeiro, RJ, 21045-900, Brazil
Traub-Cseko, Y.M., Department of Genetics, Oswaldo Cruz Institute, Rio de Janeiro, RJ, 21045-900, Brazil

The genetic structure of Brycon opalinus (Brazilian freshwater fish species) from seven wild populations across Paraíba do Sul basin and one cultured population was investigated using 7 microsatellite loci. Polymorphism at all loci was assessed with a total of 162 different alleles found. The observed heterozygosity (Ho) ranged from 0.23 to 1.00. Almost all populations, except from Itagaçaba River, deviated significantly to HWE showing deficit of heterozygote. All populations were characterized by high microsatellite variability (mean H=85.6%). Genetic structure was evidence by a significant FST (0.0432). All pairwise distances (FST) were significant, suggesting that each population is a different unit of management. The hatchery, stocked since the 50s, showed the second great average allele number: 13.43 and a gene diversity (H; observed with microsatellite markers) equal to 0.789. This was similar to previously published mitochondrial data (h=0.753). © 2005 Elsevier B.V. All rights reserved.