OCCURRENCE OF PARASITIC ISOPOD Cymothoa epimeria IN CULTURED HYBRID GROUPER (E. fuscoguttatus × E. lanceolatus) AT BT. TAMBUN, PENANG, MALAYSIA

Kua Beng Chu*, Nuruljannah H & Nur Shikin A
 
National Fish Health Research Division (NaFisH),
Fisheries Research Institute,
Department of Fisheries Malaysia,
11960 Batu Maung, Penang,
kuaben01@dof.gov.my

The parasitic isopod genus Cymothoa Fabricius, 1793 is known as tongue-eating isopod or a production pest of marine grouper aquaculture. The isopod attaches itself to the fish's tongue and cause disruption of food intake. Due to their feeding activities and site attachment on the host, the effect caused by them should not be neglected. The current information on biology, pathogenic mechanisms, epidemiology and control methods of this isopod is limited. The aim of the study was to determine the status infestation of parasite isopod in hybrid grouper during early culture period at floating cages.

A total of 739 hybrid groupers with body weight ranging from 20g to 1kg cultured within period of 2 weeks to 9 months in floating cages at Bt. Tambun, Penang were examined for the mouth inhabiting parasitic isopod infestation. The results showed only one species of cymothoid isopod with prevalence ranging from 5 to 65 and mean intensity of one during the period of March 2016 until November 2016. The isopod was identified as Cymothoa epimeria and both adult or manca stages were observed at the mouth of hybrid grouper. The adult C. epimeria (average length 2.21 ± 0.24 cm, n=40) was first detected on 10th week after the hybrid grouper was placed in floating cages. It also indicated that within 10 weeks, manca stage went through several moulting before reaching adult stage.

The fecundity study showed each mature isopod carried 80 - 500 manca stage, which is highly productive. The adult C. epimeria releases the manca in mouth cavity and the manca will swims to mouth of new host. Once the fish was infested, the manca will stay in mouth until adult stage. Farmers need to remove the adult or manca isopod from fish mouth manually using hand else the infected grouper will show slow growth with big head and small body. The information obtained from this study showed the effect of isopod on hybrid grouper was severe. Apart from that, it can also help farmers to schedule the suitable period to remove the C. epimeria from the fish.