Effect of Temperature Fluctuation on the Indian Major Carp Labeo rohita and Cirrhinus mrigala Larvae under a Controlled Environment

Abstract

Major carp i.e., Rohu (Labeo rohita) and Mrigala (Cirrhinus mrigala) are economically very important and commonly cultured in Indian subcontinent. In Pakistan aquatic organisms especially, freshwater species are facing many environmental problems such as variation in weather pattern. Temperature fluctuation is pervasive and most common environmental factor that is very distressing for major carps. The larvae of Labeo rohita and Cirrhinus mrigala were treated with different temperatures 10, 15, 20, 25, 30, 33 and 35 °C following 28 °C acclimation temperature. Thermal variation rate was recorded 2 °C/day. Death rate of both species larvae was observed. In temperature group 10 °C, 15% and 64% mortality of Labeo rohita was observed while, in Cirrhinus mrigala 16% and 66% mortality was recorded at 14 and 10 °C respectively. When larvae of both species were exposed to 10-20 °C, significantly (P < 0.05) maximum death rate was observed at this temperature as compared to other experimental groups. Cumulative death rate of Labeo rohita and Cirrhinus mrigala were recorded 84, 43, 22, 16, 1, 2, 3% and 86, 45, 23, 17, 1, 2, 4% in 10, 15, 20, 25, 30, 33, 35 °C temperature groups, respectively. All larvae of both species died within 2 days at temperature group 10 °C and continued to die at temperature groups 15 °C and 20 °C up to 11 days. Both species larval mortality persisted in temperature groups at 25 °C up to 18 days. Simple regression analysis was applied for thermal range (T < 28 °C and T > 28 °C), variation in death per fall and elevation of ∆T = 1 °C was measured in the log-linear regression model framework. When water temperature dropped from acclimation temperature 28 °C, the accumulative death of larvae for 1 °C decrease of temperature from acclimation one, significantly (P < 0.05) was calculated in both species. When water temperature elevated from 28 °C, less steep beta coefficient was observed in Labeo rohita and Cirrhinus mrigala. 1 °C elevation of water temperature from acclimation temperature 28 °C, the accumulative death in Labeo rohita and Cirrhinus mrigala were (P > 0.05) obtained