Nile tilapia (Oreochromis niloticus) has been the most widely farmed tilapia species since the 1980s. However, Pullin and Capili (1988) found that little attention had been given to the genetic improvement of its farmed populations and that broodstocks outside Africa had been derived from very small founder populations and had probably been mismanaged, with consequent genetic drift, inbreeding depression, and introgressive hybridization with other species, notably O. mossambicus. Also in 1988, an international workshop was convened to review the status of tilapia genetic resources for aquaculture (Pullin 1988). This confirmed the wealth of tilapia genetic resources in Africa, the limited genetic diversity of tilapia broodstocks used for aquaculture outside Africa, and the need for more investment in research for the genetic improvement of tilapias.

Based upon these findings, ICLARM, in consultation with colleagues from AKVAFORSK, Norway, who had pioneered the selective breeding of farmed salmon (Gjedrem 1985) and from the Philippine Bureau of Fisheries and Aquatic Resources and the Freshwater Aquaculture Center of Central Luzon State University, Philippines, secured funding from the United Nations Development Programme (UNDP) for the Genetic Improvement of Farmed Tilapias (GIFT) project. With the help of many colleagues and institutions in Africa, Asia and Europe, four new wild founder populations of Nile tilapia (from Egypt, Ghana, Kenya and Sénégal) and populations of four strains of Nile tilapia in current use by farmers in Asia (‘Israel’, Singapore, Taiwan, and Thailand) were assembled, after strict quarantine, in the Philippines. Their performance was compared in 11 different farm environments. The surprising result was that, with the exception of the Ghana strain, the wild African strains grew as well or better than the Asian farmed strains.

A subsequent large experiment—a complete 8 x 8 dialle cross to compare the performance of all 64 possible hybrids among these strains—showed no substantial heterosis (hybrid vigor) and the GIFT project team therefore decided to pursue a strategy in which genetic material from the best families of all strains would be incorporated, according to their performance rankings, in a synthetic strain. This synthetic strain has since been subjected to selective breeding for good growth, over seven generations.

The GIFT strain of fish is being further developed through research and commercialized by a non-profit foundation, the GIFT Foundation International, Philippines. A recent project, supported by the Asian Development Bank, found the estimated yield potential of the GIFT strain to be significantly higher than that of some of the existing farmed strains in Asia, though there were some variations; for example, improvements were about 54% in Vietnam and 97% in Bangladesh (ICLARM-ADB 1998). While the information about the potentials of the GIFT fish on farms continues to grow, the GIFT fish are also under investigation to explore the basis of their domestication and the applicability of the GIFT project methods to other species. For example, a researcher at the University of British Columbia (Bozynski 1998) has found that although the GIFT team selected fish for fast growth, they have also, in this process, selected quietly behaved fish. This fits with the history of agriculture, in which docility has been one of the most important attributes for domestication. Quiet fish grow faster and their low aggression lessens some environmental risks.

References

Gjedrem, T. 1983. Genetic variation in quantitative traits and selective breeding in fish and shellfish. Aquaculture 33:51-72.

Gjerde, B. 1986. Growth and reproduction in fish and shellfish. Aquaculture 57:37-55.

Tave, D. 1988. Genetics and breeding of tilapia: a review, p. 285-293. In R.S.V. Pullin, T. Bhukaswan, K. Tonguthai and J.L. Maclean (eds.) The Second International Symposium on Tilapia in Aquaculture. ICLARM Conf. Proc. 15, 623 p.

Christine Casal and Liza Agustin