Seasonal Variation in the Occurrence of Parasitic Isopods and Copepods (Crustacea) Infecting the Clupeidaen Fishes of Malabar Coast, India
Occurrence of parasitic isopods and copepods infecting the clupeidaen fishes of
Malabar coast (India) was assessed in terms of prevalence, intensity, host/ site specificity
and seasonal variation. 3 isopods (Joryma brachysoma, Anilocra leptosoma and Agarna
malayi) and 4 copepods (Clavellisa hilsae, Peniculus fistula fistula, Pseudorbitacolax varunae
and Naobranchia cygniformis) were recovered from the fishes, Escualosa
thoracata, Tenualosa toli (hosts two parasites), Sardinella fimbriata and Anodontostoma
chacunda (hosts three parasites) respectively. The prevalence and/or intensity of each
recovered parasitic species showed statistically significant variation (P<0.05) according to
seasons; the prevalence of isopod species was high during pre-monsoon and least in
monsoon. Except P. varunae, which is more prevalent in pre- monsoon, all copepod species
exhibited high prevalence during post- monsoon. The floor of branchial cavity forms the
major site of infection for J. brachysoma and A. malayi recovered from E. thoracata and T.
toli respectively. A. leptosoma prefers dorsal body surface, behind the head of T. toli for
infection. P. fistula fistula, P. varunae and N. cygniformis prefer to infect respectively caudal
fin, anterior and posterior mucus layer of inner operculum of A. chacunda indicating their
microhabitat preference likely to avoid niche competition during the circumstance of triple
parasitism