Effects of Different Photoperiodic Regimes on the Body Mass, Behavioural and Stress Responses in Golden Mahseer, Tor putitora

Golden mahseer, Tor putitora is a teleostean cold-water fish, known to occur in the rivers of Himalayas. Light affects the physiology of the fish. Therefore, the study was carried out to evaluate the effects of different photoperiodic regimes as environmental cues on the development of body mass, behavioural and stress responses in T. putitora. Fishes were exposed in the different photoperiodic regimes such as 8 hours light: 16 hours dark (8L:16D), 16 hours light 8 hours dark (16L:8D) and natural light condition. The body mass, cortisol and behavioural profiling were studied. Ethovision (XT-13) was used to record the different behavioural responses of the fish after the exposure to various photoperiodic regimes. The difference in the behavioural profiling and scoring was recorded in the different groups of the juveniles of the fish. Effects of light: dark skeletons such as 8 hours light: 16 hours dark (8L:16D), 16 hours light 8 hours dark (16L:8D) and natural light condition (Control) exhibited remarkable differences in the biomass enhancement in the juveniles of the fish (P<0.05). Maximum amount of cortisol (0.93± 0.08ng/ml) was recorded in the group of the fish exposed to 16L:8D compared to natural (0.78± 0.21ng/ml) and the group exposed to 8L:16D photoperiodic regime (0.69± 0.11ng/ml). A significant difference (P<0.05) in behavioural profiling of the fish exposed to green, red and natural colour was noticed, where velocity/swimming speed of the fish was most affected by the green light spectra. The significant difference in the behavioural profiling and scoring was recorded in the different groups of the juveniles of the fish.