Impact of asymmetrical diurnal temperature variation on Labeo rohita

Biochemical and histopathological changes in response to environmental stress have been widely used as biomarker parameters in the evaluation of an organism’s health. In the present study, an attempt has been made to evaluate the impact of asymmetrical variation in diurnal temperature on growth, histopathology, and tissue proximate composition of the Indian major carp Labeo rohita. In this respect, two different experiments were carried out in outdoor (Experiment) and indoor culture systems (Control) in one-tonne FRP tanks in duplicate. In each system, sixty fingerlings of L. rohita were reared for five months. In the experimental system, the temperature range recorded was from 24.58°C to 37.38°C, with the maximum monthly average value of 35.58 ± 1.37°C. However, in the control system, the range of water temperature recorded was from 26.38°C to 31.07°C, with the maximum monthly average value of 29.25 ± 0.86°C. More or less a similar range of variation was noticed for other tested parameters except pH value, wherein the variation was not obvious. The results on the growth responses of the experimental group were high compared with the control group cultured in an indoor culture system. In association with growth responses, the biochemical constituents such as protein, carbohydrate, and lipids in the muscle, gill, kidney, and liver tissues of L. rohita reared in the outdoor culture system were more when compared with control group fishes. Histomorphological changes in the gill, liver, kidney, and muscle tissues of L. rohita cultured in an outdoor culture system showed marginal structural variations compared to a control group of fishes.