Success Stories In Asian Aquaculture - Library - Network of ...

152 B.O. Acosta and M.V. Gupta8.2 Why is the Need for Genetic Improvement of Fish?The green revolution of the 1960s and 1970s, with its package of geneticallyimproved seed, farm technology, and better farm inputs, has been responsible forthe enormous increases in crop yields in many developing countries (FAO 2001) .While significant production gains have been made in the case of crops, livestock,and temperate fish such as salmon, no efforts were made until the 1980s for thedevelopment of improved strains or methods for genetic improvement of tropicalfinfish, which contribute to over 50% of the global aquaculture production. It hasbeen estimated that less than 1% of the global aquaculture production comes fromgenetically improved stocks, indicating enormous potential for production gainsthrough the use of improved strains in aquaculture. Further, it has been shown thatin many cases, the cultured stocks are inferior to the wild populations due toinbreeding (Pullin and Capili 1988) .In view of the above mentioned facts, the WorldFish Center, in collaborationwith the national partners in Philippines and Norway, initiated a research in 1988to develop methods for the genetic improvement of tropical finfish, using tilapia asa test species.8.3 Why Tilapia?Tilapias are farmed in at least 85 countries, because of many desirable qualitiessuch as the ability to survive and grow in shallow and turbid waters, suitability forculture in low-input extensive systems to high-input intensive systems, and comparativelyhigher resistance to diseases and parasites when compared with otheraquaculture species (Pullin 1983 ; Eknath 1995 ; Gupta and Acosta 2001a) , withmost production from the developing countries of Asia and Latin America. In aquaculture,tilapias are regarded as opportunistic omnivores and herbivores feeding onphytoplankton and detritus, just like the world’s principle farmed livestock(Beveridge and Baird 2000) . It is considered as a poor man’s fish and/or an “aquaticchicken.” With increasing popularity among consumers, tilapias have become theworld’s second most popular farmed fish, after carps. Global production of farmedtilapia reached 2.3 million tons in 2006, valued at about $2.4 billion (Fitzsimmons2008) . Because of the abovementioned qualities and short generation time of aboutsix months and its suitability for the application of genetics in aquaculture, fromconservation of genetic resources to breeding programs, tilapia was considered asan ideal species for developing methods for genetic improvement of tropical fish.Studies conducted by the WorldFish Center and its partners during the 1980sfound that Asian tilapia stocks were of poor genetic quality and this was largelyattributed to poor broodstock management, resulting in inbreeding and widespreadintrogression of genes from undesirable feral O. mossambicus (Macaranas et al.1984 ; Macaranas et al. 1986 ; Taniguchi et al. 1985; Eknath et al. 1991) . A review ofthe history of introductions and subsequent transfers of O.niloticus also revealed that