Impact of Temperature Gradient on the Indian Major Carp Catla catla Larvae

Catla catla (Family: Cyprinidae) were exposed to 10, 15, 20, 25, 30, 33 and 35 °C following 28 °C acclimation temperature. Temperature change rate was 2 °C/day. Mortality rate of fish was recorded. In 10 °C temperature group, 17 and 65 % mortality was recorded at 14 and 10 °C, respectively. Significantly (P < 0.05) higher mortality was recorded in fish exposed at 10–20 °C as compared to other treatments. Cumulative mortality rates were 89, 43, 24, 18, 1, 2, and 3 % in fish exposed at 10, 15, 20, 25, 30, 33, and 35 °C, respectively. In 10 °C temperature group, all fish died within 2 days, whereas in 15 and 20 °C temperature groups, mortality was continued up to 11 days; it was 18 days in 25 °C temperature group. With simple regression analysis for the temperature range (T < 28 °C and T > 28 °C), percentage changes of mortality per fall and increase of ΔT = 1 °C was calculated in the log-linear regression model framework. When temperature was reduced from 28 °C, the cumulative mortality increment in each 1 °C fall was e.109 = 1.115 (P < 0.05). High R-square value indicated a high variation (96.8 %) in log-transformed mortality for temperature difference. Beta coefficient was less steep when temperature increased beyond 28 °C. The cumulative mortality e.075 = 1.077 (P > 0.05) was obtained for each 1 °C increase of temperature from 28 °C. © 2014, The National Academy of Sciences, India.