Infestation of isopod Norileca indica in big-eye scad Selar crumenopthalmus off Panay Gulf, Philippines

The big-eye scad Selar crumenopthalmus is a commercially important fish species in the Philippines and is not exempted from parasite infestation. Thus, study aims to determine the prevalence and intensity of isopod infestation in fish, percentage reduction of respiratory surface area of gill filaments and condition factor of the fish. A total of 274 fish samples (mean FL 142 ± 5.88 mm) were collected and examined from Panay Gulf, Philippines. The prevalence and mean intensity of isopod, Norileca indica is 9.49 % and two isopods per fish (mean FL 142 ± 5.88mm), respectively. In fish samples with infestation in both pair of gills, the percentage reduction in gill area decreases in line with increasing fish length. However, there is no significant difference between the reductions of gill area of uninfested and infested fish (p > 0.05). Moreover, there was also no clear trend and no significant difference in the condition factors of infested and uninfested fish (p > 0.05). Presence of the parasite may hinder in the food intake of fish and may prevent supply of blood to other parts of fish body which may led to stunted growth of host fish. However, fishes infested with parasite were not significantly considered as less healthy as cause of the infestation of isopod without considering other factors that would affect the fish overall state. Highlights In fishes infested with male isopod on one side and female isopod counterpart on the opposite side showed that the percentage reduction in gill area decreases in line with increasing fish length Isopod infestation in fish is not highly correlated with poor health condition of the host fish. There is no significant difference in the percent gill surface area reduction and condition factor of Norelica indica infested and uninfested fish.