The Roach, Rutilus rutilus caspicus, is a potential for commercial aquaculture in Iran.one of the most significant constraints limiting commercial production of Roach is the lake of a reliable supply of eggs and Larvea. A narrow window of annual spawning prevents year-round availability of juveniles for grow out. The present study reports the use of photoperiod manipulation to alter the time of spawning in female R. rutilus caspicus and increase availability of larvae. Adult female Roach were maintained 70 days under a simulated natural light (NL) and 16L/8D, 11L/13D and 9L/15D photoperiod regimes. Water temperature was adjusted on 14, 20 and 24ºC. reproductive development was monitored by histological analysis of gonadal biopsies and plasma level of 17β-stradiol and 17α-hydroxy progestron as main sexual stroids were investigated as well.The results showed that, Follicle growth and spawning in females were advanced approximately two months by exposure to the long day regime. This research also suggested that, in the process of oocyte maturation of Roach, photoperiod appears to be more affective than temperature, for even in the lowest experimental temperature (14°C), the fish exposed to the long photoperiod, had earlier maturity and spawning in compare to natural light regime. These finding suggest that photoperiod manipulation can be used to alter the reproduction cycle in Roach and control the supply of eggs for commercial aquculture
