GENETIC-IMPROVEMENT OF FARMED TILAPIAS - THE GROWTH-PERFORMANCE OF 8 STRAINS OF OREOCHROMIS-NILOTICUS TESTED IN DIFFERENT FARM ENVIRONMENTS

Results from two consecutive generations of testing to evaluate the gr owth Performance of eight different strains of Nile tilapia (Oreochrom is niloticus) in eleven different farm environments are reported. The eight strains include four new strains recently imported to the Philip pines from Egypt, Ghana, Kenya and Senegal; and four established Asian farmed strains popularly known in the Philippines as 'Israel', 'Singa pore', 'Taiwan' and 'Thailand' strains. The test environments were cho sen to cover a wide range of Philippine tilapia farming systems, from simple ponds, as used by backyard farmers, to more intensive systems: fertilized ponds, ponds fertilized with on-farm agricultural residues, rice-fish systems, cages, and three tilapia hatcheries (satellite sta tions) located in different regions of the island of Luzon. During the first generation trials in 1989, individually tagged fingerlings bred from the founder populations (total 7652) were communally reared in a ll test environments for about 90 days. In 1990, the second generation trials were made as a part of a complete diallele crossing experiment (8 X 8 strains). Data on 3420 individually tagged fingerlings of pure strains communally reared in eight test environments were used for th e study. The results indicated highly significant differences among th e growth performances of the eight strains. Moreover, with the excepti on of the Ghana strain, the newly introduced African wild strains perf ormed as well as or better than the most widely farmed Asian strains. The importance of strain X test environment interaction over the inves tigated range of test environments was low. The implications of these results for developing a breeding program for tilapias in the Philippi nes are discussed.