Seasonal prevalence on the Parasitism of Istiophorus platypterus (Shaw, 1792) by Pennella sp. (Copepoda: Pennellidae) from the Tamil Nadu Coastal waters, India

This study investigates the parasitism of Indo-Pacific sailfish along the Tamil Nadu coastal waters during the December 2023 and November 2024.The examination of 1,207 fish specimens were collected from three landing stations: Annan Koil, Mudasalodai, and MGR Thittu, where we have found 142 infested fish, thereby reporting an overall prevalence of 11.76%.Station-specific prevalence rates were 11.53% at Annan Koil, 12.5% at Mudasalodai, and 11.21% at MGR Thittu.The prevalence was the highest during the summer season (March-May) and the lowest during the monsoon (September-November).The anatomical and morphological studies of the parasites showed attachment to the dorsal and lateral surfaces of the host, with key diagnostic features being cephalothorax, antennary processes, and egg sacs.Chi-Square statistical analyses revealed significant differences in the prevalence and intensity of infestation between stations (p < 0.05).Mudasalodai had the highest mean intensity (2.4 parasites per infected fish), followed by Annan Koil (1.7) and MGR Thittu (1.5).Seasonal variation showed higher infestation intensities during the summer and post-monsoon periods.These findings highlight the influence of seasonal factors on the parasitic infestation dynamics of Pennella sp. in the coastal waters of Tamil Nadu.