The crescent perch, Terapon jarbua, is a medium-sized, euryhaline fish of ecological and economic importance, contributing to demersal fisheries and the marine ornamental fish trade in India. Genetic diversity and population structure of T. jarbua along the Indian coast were assessed using 145 partial sequences (506 bp) of the mitochondrial D-loop region. Populations exhibited high haplotype and nucleotide diversity. A total of 96 haplotypes were identified, with several shared among geographically distant populations. The results revealed high within-population variation and broad genetic connectivity of T. jarbua along the Indian coast, with evidence of partial genetic structuring and low-to-moderate differentiation in some pairwise comparisons. Neutrality tests and mismatch-distribution analyses provided suggestive evidence of historical demographic expansion. High genetic diversity and demographic patterns consistent with a possible historical expansion suggest a complex demographic history, including a possible population expansion during the Pleistocene epoch. These findings provide baseline information for future genetic assessments and the sustainable management of T. jarbua in Indian waters.
