Effect of light intensity on survival, growth and physiology of rohu, Labeo rohita (Cyprinidae) fry.

Purpose: Light intensity is one of the important environmental factors that have strong influence on larviculture. Culture of fish at high intensity of light generates harmful radicals in the body that can compromise their health and production. The present study aims to evaluate the effect of various light intensities on the physiology of rohu Labeo rohita fry.Materials and Methods: Rohu fry (13.56 ± 0.4 mg) were exposed at five different light intensities: 0.17 ± 0.005 (Lc, control), 1.45 ± 0.23 (L1), 2.69 ± 0.47 (L2), 3.93 ± 0.72 (L3) and 5.06 ± 0.95 Wm-2 (L4). After 90 days of culture, rohu were harvested.Results and Conclusions: A 2-5% mortality of rohu was recorded in L3 and L4 treatments. The average weight and specific growth rate were significantly (p < .05) higher in Lc treatment compared to others. The light intensity and swimming activity of rohu showed direct relationship, whereas, light intensity showed inverse relation with nitric oxide synthase and reduced glutathione levels. Significantly (p < .05) higher glutathione S-transferase and glutathione peroxidase activies were found in rohu exposed at L4 treatment. Higher light intensities resulted in oxidative stress in the muscles of rohu. Thiobarbituric acid reactive substances, carbonyl protein and heat shock protein 70 were significantly (p < .05) higher in rohu exposed at L4 compared to other treatments. Exposure of rohu fry to intense light resulted into physiological stress and immunosupression.