Procedures. To ensure high genetic variability before selection, a synthetic base population was built from the 25 best-performing groups of the 64 tested. The development and characteristics of this synthetic base population have not yet been adequately described in a peer-reviewed journal, but this is to be remedied in 2005.26 The synthetic base population was the genetic material used for selective breeding to develop GIFT. To select for weight at harvest, starting with the base population and continuing for successive generations, 200 tilapia families were established in