Infection parameters of Norileca indica and a new record of Ceratothoa carinata (Crustacea: Isopoda: Cymothoidae) on Selar crumenophthalmus (Actinopterygii: Carangiformes: Carangidae) in the waters of the Sibuyan Sea, the Philippines

Studies on cymothoid isopods as parasites affecting the marine fisheries and aquaculture industries are relatively scarce in the Philippines despite having detrimental impacts on their fish hosts. Parasitological examination on the bigeye scad, Selar crumenophthalmus (Bloch, 1793), a potential aquaculture species, in the waters of the Sibuyan Sea, Philippines was done on fish specimens collected on 21 April 2021. Out of the 88 specimens, a total of 13 big eye scads were infected with cymothoid isopod Norileca indica (Milne Edwards, 1840), found in the branchial cavities of the fish, resulting in a prevalence of 14.77%. A total of 20 individual isopods (13 females and seven males) were recovered, with a mean intensity of 1.53. Based on the morphological characteristics and as confirmed by the cytochrome oxidase subunit 1 ( CO1 ) sequence, one host fish was also infected with Ceratothoa carinata (Bianconi, 1869). This appears to be the first record of C. carinata from the Philippines. To fully understand the implications of cymothoid parasites on the bigeye scad, further studies are recommended to account for the impacts of seasonality, reproductive stages of the host fish, and effects of abiotic factors such as water movement and depth.