Parasitic copepods are a significant ectoparasites of marine and estuarine fishes, often causing tissue damage, physiological stress, and reduced host fitness. This study reports the first confirmed occurrence of Lernaeenicus hemiramphi (Yamaguti 1939) parasitising the halfbeak fish Hemiramphus marginatus (Forsskål, 1775) from the southeast coast of India. A total of 127 fish specimens were collected from Parangipettai coastal waters between March and June 2025. Four fish (3.15%) were infested, with a mean intensity of 1.25 parasites per infected host. All parasites were found deeply embedded in the lateral musculature, a site rarely reported for Lernaeenicus spp. Morphological analysis confirmed them as female parasites with evidence of egg strings. Histopathological examination revealed significant inflammatory cell infiltration, localized haemorrhages, and muscle necrosis at the attachment sites, indicating severe tissue damage. Despite the localized pathology, no significant differences in Fulton’s Condition Factor (K) were observed between infected and ininfected individuals, suggesting that the low intensity of infection did not impact overall host condition. This study expands the known host range and geographical distribution of L. hemiramphi and highlights the pathological significance of musculature-embedded copepods in Indian marine ecosystems.
