Abstract
Understanding evolutionary processes reshaping the genetic structure in the context of environmental changes is an important component of sustainable management for the fisheries resources. In this study, we analyzed mitochondrial control region sequence to reveal population structure, phylogeog-raphy and demographic history of six populations of hilsa shad (Tenualosa ilisha) in the Indian Ocean regions (Andaman Sea, Bay of Bengal, Arabian Sea and Persian Gulf). High haplotype diversity was found in all of the populations of T. ilisha. The Analysis of Molecular Variance and FST comparisons revealed high level of genetic variation and divergence between populations of the Bay of Bengal and Arabian Sea. Four cryptic genetic barriers were found for the studied populations of T. ilisha, and the highest degree of population divergence was found between the Western Indian Ocean (Arabian Sea and Persian Gulf) and Eastern Indian Ocean (Andaman Sea and Bay of Bengal) regions based on the Voronoi tessellation of BARRIER analysis. The gene flow analysis detected almost no migration between Eastern and Western part of the Indian Ocean regions. Besides, one-way migration was found from Pakistan of Arabian Sea to Kuwait population of Persian Gulf. Demographic history of population expansion and long stable population varied for different populations of hilsa shad. Distinct cryptic genetic barriers, limited gene flows and complex evolutionary process resulted in a significant population genetic and phylogeographic structure, and intricate demographic histories of T. ilisha populations. Further, the study provided valuable insights for conserving and managing of this fishery resource in its broad geographical coverage.