Determination of early life stages of fish for thermal tolerance, optimum temperature for growth, rate of oxygen consumption is becoming essential for aquaculture industry in the climate change scenario due to long-term and short term (seasonal and diurnal) variability in temperature. Emphasis was made to understand the response of early of rohu (0.09 to 0.1 g) to thermal acclimation. Three hundred early fry stage rohu, Labeo rohita (initial weight 0.097±0.01 g) were equally distributed at four different temperatures (28, 30, 32 and 34°C) each with three replicates for a period of 40 days. Highest body weight gain was between 30 and 32°C and lowest feed conversion ratio (FCR) was at 30°C. The percentage weight gain and specific growth rate at 30°C were 382±8.01 and 0.88±0.03% respectively, significantly higher than other acclimation temperatures. Thermal tolerance and oxygen consumption rate were analyzed to determine the temperature tolerance limits and metabolic activity at four acclimation temperatures. Critical thermal maxima (CTmax) was 42.86±0.04, 43.3±0.02, 44.45±0.02 and 45.42±0.03; critical thermal minima (CTmin) was 13.07±0.04, 14.35±0.02, 14.92±0.04 and 15.64±0.03 and oxygen consumption rate was 110.75±0.44, 126.57±0.60, 146.22±0.68, 166.47±0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34°C respectively and increased with increasing acclimation temperatures. Oxygen consumption rate for four acclimatization temperatures increased significantly, 110.75±0.44, 126.57±0.60, 146.22±0.68, 166.47±0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34°C respectively. Temperature preference of the early fry of rohu derived from relationship between acclimation temperatures and Q10 values for 28 to 30°C, 30 to 32°C, 32 to 34°C were 1.94, 2.05, and 1.91 respectively. The optimum temperature range for growth was 30 to 32°C and Q10 value was 32 to 34°C. Survival at different acclimation temperatures was between 98.7±2.31, 96.0±4.0, 93.3±2.31 and 94.7±4.62%, from lower to higher acclimation temperatures.
Key words: Acclimation temperature, critical temperature, critical thermal maxima (CTmax), critical thermal minima (CTmin), Labeo rohita.
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