Monosex female production in the silver barb ( Puntius gonionotus Bleeker)

This paper describes hormonal masculinisation of genetically female, gynogenetic silver barbs ( Puntius gonionotus) and the results of crosses between such neomales and ordinary females. Gynogenetic fish (previously shown to be all females) were used in trials on hormonal masculinisation to simplify assessment of the results. Treatment with 25 mg kg −1 17α-methyltestosterone in the diet for 4 or 5 weeks, starting at two weeks post-hatch, produced 33.9% and 29.8% males, respectively. The majority of crosses between such males and ordinary females gave all-female progeny, which supports the hypothesis of female homogamety and establishes that large-scale production of monosex females is feasible in this species. A growth trial comparing monosex female groups to mixed-sex groups in pond culture showed an increase in yield from the monosex groups. The implications of the results for commercial production of monosex female silver barbs are discussed.