By contrast, the estimate of genetic gain from Khaw et al. (2008b) may actually be biased downwards. Firstly, the frozen sperm was collected from the best growing males in the base population, whereas the sires used from the ninth generation were not the best (they were close to the average of that generation). Secondly, the formal GIFT selection program ended at the fifth generation, and there was no selection when matings were conducted to produce the sixth and seventh generations. The sixth generation was sent to Malaysia and was used there to establish the population now located in Jitra Aquaculture Extension Center, Kedah state. That means in between these nine generations, there are two in which no selection of superior individuals for growth rate or any other trait was conducted. If allowance were made for this when calculating genetic gain per generation, a figure (9%) closer to that reported by Eknath et al. (1998) would be obtained.