Aim: The study assessed the effect of different concentration of dissolved oxygen in Tor putitora, commonly known as Golden mahseer on physiological activities of juveniles regarding their growth performance, behavioural response and stress. Methodology: Twenty-seven acclimatized fingerlings of Tor putitora were selected for the experiment, in which nine were exposed to each group of dissolved oxygen treatment (Natural, 6.76 mg l-1, low 4.81mg l-1 and high, 10.20 mg ml-1) in aquaria (60×30×30) cm. The body weight (g), cortisol concentration (ng g-1) and behaviour profile was assessed using the Ethovision XT-13 software (Noldus, Info Tech, Wageningen, The Netherlands). Results: The average value of body weight (g), cortisol concentration (ng g-1) and all behavioural profiles of Tor putitora showed a significant difference at P<0.05. The average concentration of cortisol was lower in high oxygen dissolved exposed juveniles as compared to other oxygen treatment groups. Interpretation: High oxygen content in water bodies reduces the stress level and stereotyped behavioural responses of fishes. These novel data, on cognitive swimming pattern in Tor putitora, is quite important for enhancement of production and maintaining the fish health issues. Key words: Behavioural profiling, Cortisol, Dissolved oxygen, Stress, 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.