Abstract
Square-tailed mullet (Ellochelon vaigiensis) is a monotypic species of the genus Ellochelon; however, due to morphological similarities between mullet species, determining their genetic relationship and diversity provides valuable information for classification. The genetic diversity of the square-tailed mullet collected at four Vietnamese Mekong Delta (VMD) sites was examined by sequencing Cytb gene sequences. Five haplotypes were recorded from 12 Cytb gene sequences of 792-843 bp long, including 786 invariant (monomorphic) positions and six polymorphic positions. The square-tailed mullet had a high haplotype diversity (Hd = 0.79) and low nucleotide diversity (π = 0.004). Low intraspecific genetic difference was recorded in E. vaigiensis collected in sampling sites (0.3%-0.5%). Phylogeny analysis indicated that all square-tailed mullets belonged to one provisional lineage and were separated from the control square-tailed mullet lineage. More studies on the lineage of E. vaigiensis in VMD are necessary, thereby providing scientists with information about the genetic diversity of this species in the Mekong Delta.