Molecular studies, disease status and prophylactic measures in grouper aquaculture: Economic importance, diseases and immunology

Groupers are potentially important and economically valuable aquaculture species in Southeast Asian countries. Among sport and artisanal fishers is a prized catch demanding lucrative price. Groupers belong to the subfamily Epinephelinae, which include 159 species under 15 genera; they are widely distributed in the tropical and sub-tropical waters of Atlantic Ocean and Mediterranean Sea. Grouper culture was first introduced in the early 1970s in Singapore, Malaysia, Hong Kong, Thailand, and Taiwan, and is now widely practiced throughout Southeast Asia. At present, its production is essentially in the hands of small-scale farmers; however the interest in its larger scale production in offshore systems is gaining momentum. In recent years the global production of groupers has increased tremendously due to its escalated demand with 60,774, 99,378, 163,093, and 198,690 mt in 1990, 2000, 2005, and 2007 respectively. Despite the wholesale premium price of up to US$100/kg groupers fetch in the Chinese live-fish markets in Hong Kong and South China its culture is ravaged by various diseases; for instance the large-scale seed production of groupers continues to encounter increasing difficulties, especially with a host of infectious diseases including various viral, bacterial, and parasitic pathogens and non-infectious (environment, management, and nutritional) disease agents and a number of undiagnosed diseases of unknown origin. Apart from some documented viral problems in Southeast Asia in groupers, little is known about the impact of major diseases that may go beyond direct mortalities and production losses. Immunization with formalin-killed viral and parasitic vaccines increased survival rates and dietary administration of DHA/EPA, L-ascorbic acid, vitamin C and E, sodium alginate, κ-carrageenan yeast, probiotics, and herbals significantly increased the specific and non-specific immune response and protect from diseases. In this review will discuss the available information on infectious diseases and its immune status in grouper culture.