Comparison of the effect of different photoperiod regimes on growth and feed conversion rate of Iranian produced rainbow trout (Oncorhynchus mykiss) and fish produced of eyed eggs from France

To determine the reaction to the different photoperiod regimes of Iranian produced rainbow trout and fish produced of eyed eggs from France, fish were kept under four photoperiod (light: dark, L:D) cycles (24L:0D, 16L:8D, 12L:12D, 16D:8L). In French rainbow trout, weight gain was higher in the (24L: 0D) photoperiod, but did not significantly differ from the (16L: 8D) photoperiod (p>0.05). Increase in total length and specific growth rate were significantly higher in (24L: 0D) photoperiod than other treatments. Condition factor in (24L: 0D) photoperiod, was higher than other treatments but did not significantly differ from the (16L: 8D) and (12L: 12D) photoperiods (p>0.05). In these fish, the feed conversion rate in the (24L: 0D) photoperiod, was significantly lower than other treatments. In the Iranian rainbow trout, weight and total length gain were significantly higher in the long photoperiod (16L: 8D) than other treatments. Specific growth rate and condition factor were higher in the long photoperiod. Also, feed conversion rate was significantly lower than other treatments in the long photoperiod (p<0.05). Indeed, survival in both experiments was not affected by photoperiod manipulation. As result, for higher growth and lower feed conversion rate, the continuous (24L: 0D) and the long photoperiod (16L: 8D) are recommended respectively for fish produced of eyed egg from France and Iranian produced rainbow trout.