Diversity and prevalence of parasitic copepods on Spanish mackerel <i>Scomberomorus commerson</i> with redescription of <i>Caligus infestans</i> from Terengganu, Malaysia

The Spanish mackerel Scomberomorus commerson is an economically important fish species in Malaysian fisheries. This study investigates the diversity, prevalence, and intensity of parasitic copepods found in Spanish mackerel from Terengganu, Malaysia with a redescription of Caligus infestans. Nine fish specimens were collected from three wet markets and their gill filaments were examined for the presence of parasitic copepods. The collected copepod specimens were identified to the species level, revealing three species from the family Caligidae; Caligus asymmetricus, Caligus infestans and Caligus cybii as well as one species from the family Pseudocycnidae, Cybicola armatus. Species prevalence ranged from 22% to 100%, with C. armatus being the most dominant parasitic copepods. The Cytochrome c oxidase subunit I (COI) genes of all species were sequenced, providing the first COI sequences for Caligus infestans and C. asymmetricus, while confirming the species identification of C. cybii and C. armatus. These findings provide baseline data on the diversity of parasitic copepods of Scomberomorus commerson in Malaysia, along with new locality records and DNA information for all identified parasite species.