In order to reduction of adverse effects of sexual maturation on growth and survival of rainbow trout, production possibility of all-female triploid were investigated using early heat shock on eggs which fertile by masculinized male’s sperm. Fish ploidy level was determined by erythrocyte size measurement and confirmed by gill nucleolus (NORs) counting as well as chromosome number. Sexual ratios and gonad development were determined by histological studies. Final results show that progenies which produced by mating sex-reversed (masculinized) males and normal females were totally female (100 %). Also applying early heat shocks (26.5° C lasting 20 min, 20 min after egg fertilization) were induced triploidy about 80 % in fishes. All-female triploid, all-female diploid and mixed-sex diploid fishes haven’t shown any significant difference in incubation stages (eyed-stage egg rate, hatching, survival from hatching to active feeding), (P>0.05). Eyed-stage eggs rate, and hatching rate of eyed eggs in mixed-sex triploids was significantly lower than other treatments (P<0.05). Testes development in diploid males was similar to those of triploid and was in early stages of spermatogenesis in 8 month age fish. Also diploid ovaries were packed with oocytes at previtellogenic or perinucleolus stage. But triploid ovaries although showed the distinct lamellar structure of an ovary, contained no oocytes.
