The present study was carried out to accomplish functional sex reversal by oral treatment of methyltestosterone to get XX male which sire all female progenies. The fry were fed with diet supplemented with methyltestosterone at the concentration of 1 ppm, 5 ppm and 10 ppm for 58 days starting from the swim up stage, after which they were fed normal diet No female having normal ovaries was observed at the end of the treatment. On the other hand, percentage of males ranged from 60-88 depending on the concentration of the hormone at the termination of the experiment. high mortality was recorded during the hormone treatment.
Twenty fish of 1 ppm group were reared to check the sex ratio of F₁ generation. Eleven males and 7 females survived to maturity and were fertilized individually. In progeny test, 2 males produced nearly all female progenies and the others produced 1:1 sex ratios. This fact indicates that these two were XX males functionally sex reversed from genetic females.
All produced females were normal in reproductive. function and produced 1:1 sex ratio in F₂ generation. The present data strongly suggest that rainbow trout is female homogamety (XX) and functionally sex reversed XX male produces all female progenies with normal reproductive function.