Effects of three levels of Rainbow Trout male age (2+, 3+ and 4+ years old), on duration of sperm motility, spermatocrite and eyed egg rate in rainbow trout were studied in Kelardasht Fish Breeding Center. The sperm from 2+ year old males activated by water showed the shortest motility (24.86 sec) (P= 0.007), while those of the 3+ and 4+ years old revealed the longest sperm motility. No significant difference was found between sperm motility of the 3+ and 4+ males. The average spermatocrite in different age groups of male fish was significantly different. This was showed to be 32.66% in 2+ years and 2126 % in 3+ year's male age groups respectively. Eyed egg rate was highest in 2+ years age (86/82%), and was significantly different with the 3+ age group (P=0.02). The eyed egg rate of the 4+ age group was not significantly different with those of the 2+ and 3+ age groups
