ESTROGEN SEX-REVERSAL OF TILAPIA-AUREA

Chemical treatments were used to produce sex-reversed female (genetic male) Tilapia aurea, which can be bred to produce monosex offspring. Various combinations of estrogens, two synthetic and one natural, an antiandrogen, and a 'pituitary blocking agent' were orally administered to sexually undifferentiated fry. Treatment periods were 4, 5, 6 and 8 weeks. Seven of the 36 treatments produced more than 50% females (α = 0.05). Two treatments were more successful than the others: (1) 17-α-ethynylestradiol (EE) at 100 mg kg-1 diet in combination with methallibure (ME) at 100 mg kg-1 for 6 weeks and (2) EE-100 with ME-100 and cyproterone acetate (CA) at 100 mg kg-1 for 6 weeks. These treatments produced fish that were 90% female. Comparisons of the treatments with and without CA indicated that CA may lessen the hormone effectiveness of the treatments. Diethylstilbestrol was as potent as EE in comparable CA treatments. © 1979.