The experiment was conducted to determine the effects of different photoperiods and darkness on the growth and survival of juvenileCatla catla in the laboratory for 90 days. Fishes were divided into four aquaria (10 fish per aquarium), and subjected to different photoperiod regimes of 8 hours light: 16 hours dark (8L:16D), 16 hours light: 8 hours dark (16L:8D), continuous light (24L:0D) and complete darkness (0L:24D). The maximum and minimum growth was observed in the group subjected to continuous photoperiod and complete darkness, respectively. The mean body weight of these groups was significantly different (p<0.05) from other groups which was observed from day 60. Survival rate was 100 percent in all the aquaria subjected to different photoperiods except one which was under continuous dark, where 30 percent mortality was recorded. Mean final growth rate, specific growth rate and daily feed intake were maximum in the group subjected to continuous photoperiod and their means were significantly different (p<0.05) from other groups of fish of different photoperiod regime. A continuous photoperiod is suggested for better growth and survival of rearing juvenile Indian major carp,C. catla under controlled conditions.

Key words:Photoperiod,Catla catla, Growth, Mortality, Specific growth rate