National Fish Health Research Division
Title: Caligus rotundigenitalis (Copepoda: Caligidae) infestation of crimson snapper (Lutjanus erythropterus) from Sungai Udang, Malaysia: Prevalence and recovery after freshwater bath treatment
Biography: Kua Beng Chu
Crustacean parasitic infestation particulary Caligus spp on farmed fish has been reported more frequently in Malaysia since 2008. The infestation usually associated with morbidity and mortality had caused significant economic losses. Freshwater bath has been used as treatment for Caligus sp. However, the effectiveness against copepod Caligus spp infestation had never been reviewed despite high prevalence reported. The study focused on determination of inner operculum caligids C. roundigenitalis prevalence and their recovery percentage after freshwater treatment. Ninety two farmed crimson snapper weighed 11 to 360g were obtained from Sungai Udang cages monthly. Each fish was treated individually with freshwater bath. The number of copepod dislodged from fish and showed no movement after 10 minutes were recorded. The individual copepod was then removed and placed in seawater for determination of recovery percentage. Prevalence ranging from 40 to 90% of C. rotundigenitalis with average mean intensity of 6 copepods C. rotundigenitalis in individual fish were isolated from the crimson snapper. The recovery percentage in seawater of 361 copepod C. rotundigenitalis showed average 45.7% after treated with freshwater bath. The freshwater bath showed that copepod C. rotundigenitalis were able to regain movement after 2 hours in seawater. Further observation on the survival of recovery copepod C. rotundigenitalis showed 44% and 37% after 6 and 24 hours respectively. The findings showed that there was a high posibility of copepod C. rotundigenitalis to re-infect when they are introduced back into the system, leading to recurrence of copepod C. rotundigenitalis in floating cages.