Production of neo‐male mandarin fish Siniperca chuatsi by masculinization with orally administered 17α-methyltestosterone

Abstract All-female populations of mandarin fish (Siniperca chuatsi) provide economic advantages in production because of the superior growth of females relative to males. The first step to produce all-female populations was artificially induced sex reversal of female mandarin fish; beginning at 10 dph, fish (undifferentiated) were treated with dietary 17α-methyltestosterone (MT) at 50 mg/kg and 100 mg/kg dosages for 2 months. The MT treatments successfully produced all-male stocks (male rate 100%), as compared with the control group (51.11%). The survival rate of MT-treated and control groups was not significantly different. MT did not alter fish growth over the course of the experiment to 240 dph. MT treatment promoted the development of testes, and it initially inhibited gonadosomatic index (GSI) and the levels of serum steroid hormone (T and E2). Nevertheless, at the 180 dph and 240 dph, the GSI and serum steroid hormone (T and E2) levels in MT treatment groups had no significant difference with control groups. The masculinization of mandarin fish was also demonstrated by the expression patterns of sex-specific genes, dmrt1, sox9, foxl2 and cyp19a1a; the gonads of MT-treated fish exclusively expressed male-specific dmrt1 and sox9 with no expression of female-specific foxl2 and cyp19a1a.