Induced spawning in female rainbow trout Oncorhynchus mykiss by GnRH Analog

GnRHa injection could accelerate and synchronous ovulation and spawning in female rainbow trout, the mean time to ovulation was reduced from 19.6±2.45 groups 2 to 5, respectively (P≤ 0.05). Also cumulative spawning rate increased in hormonal groups; up to 8th day after first injection. The cumulative spawning rate was 47.0, 34.4, 90.0 and 56.3% in groups 2 to 5 respectively. Although, until this time none the females in control group were spawned. In the end of experimental period (day 26), this rate was completed in group 2 to 5, but only 50% of females in control group was spawned. The mean weight of stripped eggs, egg diameter and mean survival rate to the eyed stage did not show any significant difference between experimental groups (P>0.05). Testosterone levels were increased from 9.21±4.11 at time 0 to 23.47±14.29 ng/ml at 24 h after first injection, and then reduced to the basal levels in all hormonal groups (except group 5) at 72 h after first injection (10.91±3.11ng/ml) (P≤0.05). There wasn’t observed any testosterone levels fluctuation in control group