Genetic population structure of two migratory freshwater fish species (Brycon orthotaenia and Prochilodus argenteus) from the Sao Francisco River in Brazil and its significance for conservation

Previous genetic studies conducted with migratory fish populations from downstream of the Tres Marias dam in the Sao Francisco River Basin (Brazil) have documented the occurrence of population structuring, as reported for Brycon orthotaenia and Prochilodus argenteus, two commercially important species in this basin. We revisited the genetic structure of these species using microsatellites. B. orthotaenia was sampled during the spawning season and was analyzed using five heterologous microsatellites. P. argenteus was collected in the non-reproductive season and genetic analysis was conducted using ten species-specific microsatellites. For both species, genetic diversity between collection sites was similar. Considering B. orthotaenia, F-ST and R-ST estimates and the Bayesian analysis demonstrated significant differences between sites. Two well-defined populations were identified in the study area, indicating population structuring for this species. No significant differences were found for P. argenteus. These data provide information for knowledge regarding genetic structure of migratory fish species, which may contribute toward the conservation besides the understanding the biology and ecology of these important fishery resources.