Effect of sperm diluent on some reproduction indices resulting from the crossing of sex reversed male (xx) and normal male fish with female rainbow trout

Despite the importance of monosex fry production, due to incomplete gonad development in sex reversed male rainbow trout and the absence of sperm tubes, the use of diluents is necessary to improve sperm quality. In this study, in order to investigate the effect of sperm diluent on some reproduction indices, the results of experimental treatments: including (1) fertilization of diluted sperm of in sex reversed male fish with normal egg (2) fertilization of normal male sperm with normal egg and (3) fertilization of diluted normal sperm with normal egg were compared. According to the results of this study, the percentage of fertilization and eyed egg in the all-female eggs (treatment 1) were 80±1 and 79.3±0.6 respectively. Those indices in the mixed male and female population (control treatment, 2) were , 82±1. 80.3±0.6 and in treatment 3 were 72±1 and 79.3±0.6, respectively. Except for the percentage of fertilization, there were no significant differences for the other studied characteristic (P>0.05). The findings indicate an improvement in the quality of the sperm of sex reversed males using a diluent compared to the use of this substance in normal fish sperm. Increase in growth index, including specific growth rate and food conversion ratio in treatment 1 and 2 were 1.4±0.1, 0.9±0.1, and 1.3±0.1, 1.1±0.1, respectively and had a significant difference (P<0.05). The use of diluents to improve reproduction efficiency and no need to have a large number of male breeders in the farms in order to produce monosex fry, is completely desirable.