Supermale (YY-) Oreochromis mossambicus was produced for the first time by judiciously combining the endocrine sex reversal technique with selective breding or gynogenetic technique. The combination of endocrine and gynogenentic techniques incresed supermale production from 25 to 50% and reduced the time cost of production from 22 to 8 months. A programme for commercial production and maintenance of YY broodstock for large-scale generation of monosex male populations is presented
