The genetic similarity of anadromous Hilsa shad (Tenualosa ilisha) samples from four stations along the Shatt Al-Arab River was assessed using partial sequencing of the mtDNA cytochrome b gene to describe population structures and to compare samples. Two-way sequencing was conducted on 70 samples from DNA extracted from fin samples. A phylogenetic tree was structured depending on the consensus of sample sequences using the MEGA X software. Based on all the T. ilisha samples, there were two major clades on one branch that were considered monophyletic (100% bootstrap value) and the genetic distance values were in the range 0.01–0.14. The T. ilisha samples from the Shatt al-Arab stations and an India2 sample were in one clade and the other clade consisted of unrelated pairs of T. ilisha, while T. thibaudeaui was the out group. The genetic differentiation between the clades was not significant (p > 0.05) showing the two different stocks with minor genetic differences belonged to a common genetic ancestor.

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