Production of neofemale by 17β-estradiol and YY super-male breeding in mandarin fish (Siniperca chuatsi)

It is well known that mono-sex culture has the advantages of a more rapid growth rate, more uniform size and lower energy consumption of gonadal development in fish. In production practice, male mandarin fish (Siniperca chuatsi) show great aquaculture value after the overwintering stage. As a species with an XY-type sex determination system, feminizing genetically male fish into physiological female fish and breeding YY supermales is a common method used to produce all-male populations. In this study, we systematically investigated feminization of mandarin fish by indirect feeding of 17β-estradiol (E2) at different doses (200, 400 and 600 mg/kg). Neo-females were successfully yielded in all E2-treated concentrations. The sex-reversed ratios of the 200, 400 and 600 mg/kg E2-treated groups were 40%, 87% and 100%, respectively. From 45 to 135 dat (days after treatment), the gonads in the 600 mg/kg E2-treated group consisted of oogonium and previtellogenic oocytes. At 165 dat, early vitellogenic oocytes were observed in the gonads of the 600 mg/kg E2-treated group. Regarding the expression of sex-related genes, 600 mg/kg E2-treated mandarin fish presented a different gene expression pattern from that of normal males. Moreover, the growth and development status were also analysed in XY normal males and YY supermales at 360 dph, and YY supermales showed a higher number of lumina and significantly lower growth performance than XY normal males. In conclusion, we have established a technique for efficiently inducing male to female sex reversion and YY supermale breeding of mandarin fish, which provides a great foundation for the production of all-male mandarin fish.