The swim-up fry fed 3 milligrams of 17α-methyltestosterone per kilogram of diet for about 800 degree-days, led to successful production of sex-reversed male(masculinized female) population. the spermatozoa in the testes of sex-reversed males were viable, but natural fertilization was not possible because their sperm ducts were deformed. All-female population was produced by artificial fertilization with sperms from the testes of masculinized female. All- female triploids were also produced by heat shock treatment of the eggs just after fertilization. Triploids were confirmed by the analyses of erythrocytic size and number of chromosomes. The volumes of both erythrocytes and their nuclei were larger than those of diploids. The chromosome numbers of diploids and triploids were 2n=61 and 3n=92, respectively. The gonads of the triploids were histologically sterile.