Introduction Genetic biotechnologies are being used to improve fish health through conventional selection for disease resistance and through the use of molecular investigation of pathogens for characterisation and diagnosis. DNA-based technologies are being used now to characterize different species and strains of pathogens. Genetic characterisation of the pathogen may also reveal information about its origin, e.g. DNA analysis revealed two strains of crayfish plague fungus in Sweden: one from the local species and one originating in Turkey. Once the pathogen is characterized, DNA probes can be developed to screen for specific pathogens in tissue, whole animals and even in water and soil samples. These techniques are being used to detect viral diseases of marine shrimp throughout the world and for bacterial and fungal pathogens in fishes in many areas. Biotechnology provides powerful tools for the sustainable development of aquaculture, fisheries, as well as the food industry. Increased public demand for seafood and decreasing natural marine habitats have encouraged scientists to study ways that biotechnology can increase the production of marine food products, and making aquaculture as a growing field of animal research. Biotechnology allows scientists to identify and combine traits in fish and shellfish to increase productivity and improve quality. Scientists are investigating genes that will increase production of natural fish growth factors as well as the natural defense compounds marine organisms use to fight microbial infections. Modern biotechnology is already making important contributions and poses significant challenges to aquaculture and fisheries development. It perceives that modern biotechnologies should be used as adjuncts to and not as substitutes for conventional technologies in solving problems, and that their application should be need-driven rather than technology-driven. The use of modern biotechnology to enhance production of aquatic species holds great potential not only to meet demand but also to improve aquaculture. Genetic modification and biotechnology also holds tremendous potential to improve the quality and quantity of fish reared in aquaculture. There is a growing demand for aquaculture; biotechnology can help to meet this demand. As with all biotech-enhanced foods, aquaculture will be strictly regulated before approved for market. Biotech aquaculture also offers environmental benefits. When appropriately integrated with other technologies for the production of food, agricultural products and services, biotechnology can be of significant assistance in meeting the needs of an expanding and increasingly urbanized population in the next millennium. Successful development and application of biotechnology are possible only when a broad research and knowledge base in the biology, variation, breeding, agronomy, physiology, pathology, biochemistry and genetics of the manipulated organism exists. Benefits offered by the new technologies cannot be fulfilled without a continued commitment to basic research. Biotechnological programmes must be fully integrated into a research background and cannot be taken out of context if they are to succeed. Indian fisheries and aquaculture is an important sector of food production, providing nutritional security to the food basket, contributing to the agricultural exports and engaging about fourteen million people in different activities. With diverse resources ranging from deep seas to lakes in the mountains and more than 10% of the global biodiversity in terms of fish and shellfish species, the country has shown continuous and sustained increments in fish production since independence. Constituting about 4.4% of the global fish production, the sector contributes to 1.1% of the GDP and 4.7% of the agricultural GDP. The total fish production of 6.57 million metric tonnes presently has nearly 55% contribution from the inland sector and nearly the same from culture fisheries. Fish and fish products have presently emerged as the largest group in agricultural exports of India.( Marine products export review-MPEDA.,April 2006- March2007).The potential area of biotechnology in aquaculture include the use of synthetic hormones in induced breeding, transgenic fish ,gene banking , uniparental and polyploidy population and health management. Biotechnology and Fish Health Management: Disease problem area major constraint for development of aquaculture. biotechnological tools such as molecular diagnostic methods, use of vaccines and immunostimulants are gaining popularity for improving the disease resistance in fish and shellish species world over for viral diseases, avoidance of the pathogen in very important.in this context there is a need to rapid method for detection of the pathogen. Biotechnological tools such as gene probes and polymerase chain reaction (PCR) are showing great potential in this area. Gene probes and PCR based diagnostic methods have developed for a number of pathogens affecting fish and shrimp ( karunasagar ,1999). In case of finfish aquaculture, number of vaccine against bacteria and viruses have been developed. Some of these have been conventional vaccines consisting of killed microorgansism but new generation of vaccine consisting of protein subunit vaccine genetically engineered organism and DNA vaccine are currently under development. In the vertebrate system, immunization against disease is a common strategy. However the immune system of shrimp is rather poorly developed, biotechnological tools are helpful for development of molecule, which can stimulate this immune system of shrimp. Recent studies have shown that the non specific defense system can be stimulated using, microbial product such as lipopolysacharides, peptidoglycans or glucans (itami et al 1998). Among the immunostimulants known to be effective in fish glucan and levamisole enhance phagocytic activities and specific antibody responses (Sakai, 1999). Vaccines: Modern biotechnology is also of great value in the field of vaccines and immunostimulants for aquaculture species. These allow preventative measures to be taken to combat disease through vaccination or immunity enhancement. Both can be administered via additives in feeds, immersion or, in the case of the larger culture animals like fish, by injection. Genetically engineered vaccines are also being developed to protect fish against pathogens. Genetic immunisation of rainbow trout with a glycoprotein gene from the virus causing viral hemorrhagic septicemia has recently been shown to induce high levels of protection against the virus. Work is also underway on immunizing carp, salmon and other fishes with genetically engineered vaccines for other diseases. Currently, vaccines are of questionable effectiveness in crustacea and may be difficult or too costly to use in developing countries. Detecting human pathogens: The type of DNA 'probes' that are used to screen for pathogens that affect fish or shrimp could also be developed to check for pathogens that affect humans. This will become increasingly important in answering concerns in the market place about the safety of aquatic products for human consumption. These new molecular techniques are extremely sensitive and can identify pathogens in fish long before there are any clinical signs of the disease. This has implications for quarantine and the trade of aquatic species, which is currently governed by the World Trade Organisation and the Office International des Epizooties. Trade can be restricted based on the disease status of a product or a region; identification of minute quantities of a pathogen or of a new strain of an existing pathogen could change or influence existing trade patterns. Bio-remediation: Farmed aquatic animals are much more sensitive to their immediate environment than land animals. The water they are immersed in, and on which they depend for oxygen and a range of other important chemicals, also takes up their waste products and may carry pollution from the nearby environment. The process of disease in aquaculture species is thus much more strongly connected to environmental factors than would be the case say, with cattle. A further biotechnology field that has developed in aquaculture, because of the nature of this relationship, is that of bio-remediation. This refers to the use of 'friendly bacteria or 'pro-biotics' to treat water or feeds and, by natural processes, discourages the development of 'unfriendly' bacteria that potentially would cause disease. Many such products are currently being marketed' -- while conclusive studies have yet to be carried out to check their effectiveness, some of them do seem to bring production benefits. Genetic engineering processes are becoming increasingly common and are being applied to a widening variety of organisms. Genetic modification involves identifying genes scientists hope will express the desired traits when introduced into fish. These new genes can come from other species of animals, plants, bacterium, and even humans. Disease Control by Producing Transgenic Fish: There are several processes used to insert “new” DNA into fish, ranging from inserting genetic material directly into eggs to subjecting fish eggs to electrical pulses, which form pores and allow foreign DNA to access the eggs. The precise location where the new genetic material has attached to the original DNA is unknown and may vary between individual fish so scientists need to check to ensure the inserted gene is present and determine if it functions as expected. Once scientists have determined that the genes have been inserted, the fish are raised like other farmed fish. Although this discussion is focused on transgenic fish, other transgenic aquatic organisms, including marine and freshwater plants and shellfish, are being fast-tracked for commercialization. Genetic engineering technology is being applied with more frequency. These increasingly common practices, coupled with a lack of safeguards and regulations, make state action crucial to protect public and environmental health. Characterization of fish innate immunity system: Although many genes involved in the innate immune systems have been cloned from mammals, it is still not completely understood if fish have similar systems. In an attempt to clone, sequence, and characterize genes involved in the fish innate immunity system, we have recently characterized 26 CC chemokines and 7 CXC chemokines from catfish. Our results suggest rapid gene duplications of fish chemokines. We have also characterized a number of antimicrobial peptide genes including NK-lysin, bactericidal permeability-increasing protein (BPI), hepcidin, liver-expressed antimicrobial peptide 2 (LEAP-2). These genes may have potential for applications in genetic improvements of catfish.. Conclusion: Biotechnological research and development are growing at a very fast rate. The biotechnology has assumed greatest importance in recent years in the development of fisheries, agriculture and human health. The science of biotechnology has endowed us with new tools and tremendous power to create novel genes and genotypes of plants, animals and fish. The application of biotechnology in the fisheries sector is a relatively recent practice. Neverthless,it is a promising area to enhance fish production. The increased application of biotechnological tools can certainly revolutionise our fish farming besides its role in biodiversity conservation. The paper briefly reports the current progress and thrust areas in the transgenesis, chromosome engineering, use of synthetic hormones in fish breeding, biotechnology in health management and gene banking.
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