THE PRODUCTION OF FUNCTIONAL SEX-REVERSED MALE RAINBOW-TROUT WITH 17-ALPHA-METHYLTESTOSTERONE AND 11-BETA-HYDROXYANDROSTENEDIONE

The sex of gynogenetic rainbow trout was reversed to produce XX males by using two steroids, 17 alpha-methyltestosterone (MT) and 11 beta-hy droxyandrostenedione (OHA). Fish were exposed to either single or mult iple doses of steroids during various times around the period of hatch ing to determine the labile period for effective sex reversal, Steroid s were administered either by immersion (400 mu g/1 for 2 h) or a comb ination of immersion plus feeding (3 mg/kg diet for 60 days) to determ ine if males with intact sperm ducts could be produced, Immersion in M T resulted in varying degrees of masculinization while immersion plus feeding produced nearly 100% male populations. The most effective peri od for steroid immersion was 1 week after the time when one-half of th e fish had hatched. Multiple immersions in MT failed to increase mascu linizing effects, Immersion in OHA caused only low rates of masculiniz ation, while immersion plus feeding resulted in 70% male populations. Males produced through both immersion and feeding of MT generally did not develop sperm ducts; whereas animals treated by immersion alone in MT, or those produced with OHA, tended to be functional, Although fin al yields for sex-reversed males following gynogenesis were low, 1.5 a nd 1.6% for the two groups respectively, cryopreserved semen from thes e males can be used to produce all-female offspring for years, Cryopre served semen from functional males in this study produced 100% female populations.