Improving growth performance and caudal fin stripe pattern in selected F 6 –F 8 generations of GIFT Nile tilapia ( Oreochromis niloticus L.) using mass selection

Genetic improvement using the mass selection method of growth performance and stripe pattern on caudal fin in selected F 6 , F 7 and F 8 generations from genetically improved farmed tilapia strain Nile tilapia was evaluated at the National Tilapia Seed Farm of Qingdao, north China. In experiment I (2003), the average of daily body‐weight gain of F 7 was 12.5% higher than F 6 , and 28.6% higher than F 5 ( P <0.05). In experiment II (2004), the average daily body‐weight gain of F 8 was 12.9% larger than F 7 , and 56.9% larger than F 6 ( P <0.05). Coefficient of variation [(SD/mean)100] of body weight of F 8 decreased significantly ( P <0.05) to 79.7% of F 6 and 72.9% of F 7 , respectively, indicating that the growth became more synchronous after continuous selection. The percentage of fish with ideal vertical and parallel stripes on caudal fins in F 5 , F 6 , F 7 and F 8 reached 24.8%, 28.8%, 32.2% and 37.6%, respectively, significantly higher than that of the base population (17.6%) ( P <0.05).