Seasonal variation of the prevalence of cymothoid isopod Norileca indica (Crustacea, Isopoda), parasitizing on the host fish Rastrelliger kanagurta collected from the Southwest coast of India.

Parasitological investigations on the occurrence of isopod parasites in fishes collected from off Cochin coast along Southwest India was carried out for a period of 1 year from January 2018 to December 2018. Altogether 20 species of fishes were analysed from 12 families including Scombridae, Carangidae, Clupeidae, Nemipteridae, Hemiramphidae, Belonidae, Menidae, Priacanthidae, Sphyraenidae, Stromateidae, Coryphaenidae. Infestation of Norileca indica was noticed only in the host fish Rastelliger kanagurta. Totally 619 specimens of R. kanagurta were examined for the presence of isopod parasite, N. indica. Among those, one hundred and seventy five specimens were found to be infested by N. indica. Overall prevalence, mean intensity and abundance were found to be 28.27%, 1.21, and 0.342 respectively. Highest prevalence of infestation, mean intensity and abundance were recorded in the month of August 2018.