Assessment of Isopod Parasitic Infestation among Economically Valuable Marine Fish Species in Coastal Purba Medinipur, West Bengal, India

Abstract

Aims: To determine the temporal and spatial distribution of marine isopods across two sampling stations (Digha Mohana and Petuaghat) in coastal Purba Medinipur. Study Design: The current research was conducted using weekly surveys at two sampling stations. Owing to increased fishing and fish-landing activities, the surveys were conducted in the morning (6:00–8:00 a.m.) and afternoon (3:00–5:00 p.m.). Place and Duration of Study: The present study was conducted at two renowned fish landing centres, Digha Mohana and Petuaghat, in Purba Medinipur. The study lasted 6 months, from the first week of August 2025 to the last week of January 2026. Methodology: Samples were collected weekly from two fish landing centres, Digha Mohana and Petuaghat, Purba Medinipur. Isopod samples were collected and stored in glass jars containing 8% formalin solution for future research. Results: Nerocila serra and Nerocila sundaica were the most prevalent and widely distributed of the five identified species, suggesting greater adaptability to local environmental conditions and host availability. Nerocila depressa, on the other hand, was relatively uncommon, which may indicate host preference or habitat specificity. Regarding seasonal variation, the post-monsoon to early winter months (October–December) supported higher species occurrence, potentially owing to favourable environmental conditions and increased host abundance. The lower occurrences recorded in August and January demonstrate the influence of seasonal variation on isopod population dynamics. Spatial variation between the two sampling stations indicates that host distribution and local environmental conditions may affect species occurrence. Conclusion: The occurrence of these parasitic isopods at both stations implies that both sites provide suitable habitats. These findings are supported by the diversity analysis, which shows that December 2025 had the highest diversity, followed by October 2025, suggesting favourable ecological conditions.