Comparison of Growth factors in Monosex Rainbow Trout and Ordinary Fish Cultured in Raceway Pounds

In many species of finfish, females exhibit higher growth rates than males and achieve larger sizes. In addition, in some species, males mature before reaching marketable size. Therefore, there is great interest among fish farmers to produce all-female stocks. In this project we tried reversing the sex of rainbow trout larvae using 17β estradiol and direct method, further more finding the optimum dose of this natural estrogen for endocrine sex reversion of rainbow trout (O. mykiss). Treated females (12±1 g.) were tagged with implant elastomer tag (ABC tag) and released into 11 farms in Kohkiloieh, Fars and Charmahal Provinces. Each farm received 3000 tagged fingerlings. After 6 months Specific growth rate, condition factor and growth performance were calculated for each farm. Results revealed that mono-sex females have better Growth rate than other (males) and the average weight was 342±11 while 317±9 for males. Specific growth rate was 2.1, 2.2 and 1.9 for mono-sexed females, normal females and males respectively. Weight gain was 258, 261 and 232 for mono-sexed females, normal females and males respectively. Condition factor also was 1.1, 1.1, and 0.9 for mono-sexed females, normal females and males respectively. There were significant differences between Gonad weight of males (32 g.) and females (3.4 g.) (P<0.01). Results confirmed the increasing of flesh capacity production in mono-sex females of rainbow trout.