Genetic diversity of pacu for restocking programs in the Tietê and Grande rivers, Brazil

Abstract

Piaractus mesopotamicus is a tropical fish under threat because of declines in the number of wild populations. Restocking programs have been developed as a conservation method, and the genetic monitoring of populations and broodstocks is important to ensure the viability of such programs. The objective of the current, unprecedented experiment was to evaluate the genetic diversity of P. mesopotamicus wild populations (WPs) and broodstocks (BSs) using microsatellites markers for supplying the restocking programs in the Tietê and Grande rivers. Six microsatellite loci were amplified using the DNA obtained from the caudal fin of 279 adult fish. The observed intrapopulation genetic variability was high with mean heterozygosity ranging from 0.203 to 0.833. The number of alleles per locus ranged from three (loci Pme28 and Pme32) to thirteen (loci Pme4, Pme5 and Pme14), and there were allele differences between WPsxWPs and WPsxBSs. This differentiation was confirmed by the dendrogram analysis that showed three specific clusters. Four alleles were shared in the WPs2012xBSs. Positive FIS values indicated the presence of endogamy in seven out of ten samples obtained from the WPs. The AMOVA analysis and FST values indicated moderate and high genetic differences in WPsxWPs and high genetic differences in WPsxBSs. The genetic distance and genetic identity values and number of migrants confirmed these results. Adequate intrapopulation genetic variability, similarity between BSsxBSs, and genetic differences between WPs2011xWPs2012 and WPsxBSs were observed. In the wild, individuals from the restocking program were partially observed.