Species identification and cryptic diversity in Pampus species as inferred from morphological and molecular characteristics

Pomfret, which are widely distributed throughout the western Pacific and Indian Oceans, are economically important fish species. As their similar external morphological characteristics can inhibit proper species identification, numerous errors exist in the morphological characterization and DNA barcoding data of pomfret. In this study, we extensively sampled pomfret from the Indian and Pacific Oceans. Using the sampled specimens, in combination with morphological assessments, DNA barcoding, and corrected sequences of the mitochondrial cytochrome c oxidase I (COI) gene in GenBank, we attempted to resolve the classification issues surrounding this group. We identified seven valid species in the genus Pampus, of which all seven are distributed in the western Pacific and three are distributed in the Indian Ocean. Pampus argenteus, Pampus cinereus, and Pampus sp. were identified as three valid species with relatively close genetic distances and sharing a common ancestor. Significant variation between Pampus chinensis specimens from the Arabian Sea and the northwestern Pacific suggest a possible species complex. Finally, we provide an identification key to facilitate the identification of pomfret based on the major diagnostic morphological characteristics of six Pampus species collected along the western Pacific coast. On the basis of the reports on the new record of "Pampus argenteus," we found that the Lessepsian migration of pomfret was likely, with species from the Indian and Pacific Oceans spreading through the Mediterranean Sea into the waters of the eastern Atlantic. Further study is required to clarify the validity of the newly recorded "Pampus argenteus."