Eutropiichthys vacha were collected from two rivers namely Ganga (Patna, India) and Kosi (Madhepura, India) for population genetic and phylogenetic studies. Five OPA primers were used to generate the fragment patterns from the samples collected. Polymorphisms within and between populations were assayed using 5 random primers, and 45 loci were amplified ranging from 250 to 2,000 bp. The percentage of polymorphic loci was found 51.1% and 55.6% for Ganga and Kosi populations, respectively. Total genetic diversity was 0.2173, and the average coefficient of genetic differentiation was 0.0958. The...