The world demand for fish and fishery products is increasing steadily and it is
generally accepted that it will not be possible to meet the heavy demand with resources
exploited from capture fishery alone. Now aquaculture is well established and fastdeveloping
industry in many countries and is a major focus sector for development.
During recent decades, aquaculture has gained momentum, throughout the world
especially in developing countries. According to Food and Agricultural Oganisation
(FAO, 2000), global aquaculture production was 26.38 tones in 1996 have reached
32.9 million tonnes during 1999. Only marine aquaculture sector has contributed 13.1
million tonnes during 1999.India is a major fish producing country. About one half of lndia’s brackish
water lands are currently being utilized for farming in order to reduce the gap between
supply and demand for fish. Aquaculture has become a major source of livelihood for
people and its role in integrated rural development, generation of employment and
earning foreign exchange, thereby alleviating poverty is being greatly appreciated
around the world.Among the infectious agents, bacteria are becoming the prime causal
organisms for diseases in food fishes and other marine animals. Sindermann, (1970)
reported that bacterial fish pathogen most commonly found among marine fishes is
species of Pseudomonas, Vibrio and Mycobacterium. These can be categorized into
primary pathogens; secondary invaders that may cause systemic disease in
immunocompromised hosts; and normal marine flora which are not pathogenic but
may occur on body surfaces or even within the tissues of the host. I-Iigh density of
animals in hatchery tanks and ponds is conducive to the spread of pathogen and the
aquatic environment with regular application of protein rich feed, is ideal for culturing
bacteria. Bacteria, which are normally present in seawater or on the surface of fish, can
invade and cause pathological effects in fishes, which are injured or subjected to other
environmental stresses.Mycobacteria except parasites are known as nontuberculosis mycobacteria
(NTM), atypical mycobacteria or mycobacteria other than tuberculosis(MO'l'l"). This
group of mycobacteria includes opportunistic pathogens and saprophytes.
Environmental mycobacteria are ubiquitous in distribution and the sources may
include soil, water, warm-blooded as well as cold-blooded animals. Disease caused by
environmental mycobacterial strains in susceptible humans (Goslee & Wolinsky,
1976; Grange, 1987), animals and fishes are increasingly attracting attention. Greatest
importance of environmental mycobacteria is believed to be their role in
immunological priming of humans and animals, thereby modifying their immune
responses to subsequent exposure to pathogenic species.