MANAGING PATHOGENS OF DISEASES IN MARINE FISH CULTURE IN FLOATING CAGES AND DISEASE MANAGEMENT PROTOCOLS

The study of diseases in marine fish cultured in floating cages in Peninsular Malaysia was undertaken by fish disease research group at Universiti Sains Malaysia, Penang between 1985 to 1999. During these period of studies, many parasites and bacteria pathogens were identified, diseases symptoms recorded and seasonal disease outbreaks observed. The author was a consultant to the newly established Intervet Norbio Singapore Pte Ltd from 2003-2005. During these period, Iridovirus, Nodavirus and Streptococcus iniae and S. agalactiae were confirmed as present in marine fish cultured in Malaysia. Many parasites and bacteria pathogens infecting marine fish culture in Malaysia were also found in same fish species cultured in other Southeast Asia countries. These studies on parasites and diseases were documented and published in 2014 as 'PARASITES AND DISEASES OF WARM WATER MARINE FINFISH IN FLOATING CAGE CULTURE".

Scratches and hemorrhages on body surface, tail and fin rot with loose scales were frequently observed in diseased fish, as well as many dead fish recovered at the bottom of the net, when on net changing. Accumulated loses can be as high as 80% in any one batch of fish. Freshwater treatment of fish diseases was routinely undertaken by fish farmers since the eighties. They used this method of treatment to remove the "white worm" from the fish. They had some success in reducing mortality, with reasoning that they had to reduce these "white worms". Some time, this method of treatment did not solve their problem, resulting with continuing mass mortality of the fish in the cage.

The most problematic pathogens in marine fish culture are the populations of capsalid monogeneans and leech that are found throughout the external surface of the fish. The current study is to determine what happen to the populations of the capsalid monogeneans and leech when they are treated with freshwater. This is then following up with a determination of how rapid they re-infect the fish. The results of these studies are used to determine how frequent one has to change the net to manage a reduce populations of the pathogens so as to reduce mortality in the cage. Preliminary results of these studies will be presented.

After 30 years of research on diseases of marine fish culture in floating cages, a brief outline of protocols for diseases management is suggested. Each fish farm would have to examine the suggestion to determine how to adapt it to its farm.  Fish farmers should voice out their problems in such meeting to seek assistance for solutions to their problems in the farms.