Improving growth performance and caudal fin stripe pattern in selected F6–F8 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 F₆, F₇ and F₈ 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 F₇ was 12.5% higher than F₆, and 28.6% higher than F₅ (P<0.05). In experiment II (2004), the average daily body‐weight gain of F₈ was 12.9% larger than F₇, and 56.9% larger than F₆ (P<0.05). Coefficient of variation [(SD/mean)100] of body weight of F₈ decreased significantly (P<0.05) to 79.7% of F₆ and 72.9% of F₇, 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 F₅, F₆, F₇ and F₈ reached 24.8%, 28.8%, 32.2% and 37.6%, respectively, significantly higher than that of the base population (17.6%) (P<0.05).