IMPACT OF CONSTANT ACCLIMATIZATION TEMPERATURES ON GROWTH, THERMAL TOLERANCE AND OXYGEN CONSUMPTION OF EARLY FRY OF LABEO ROHITA (HAMILTON, 1822)

Abstract

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 longterm variability in temperature and the seasonal and diurnal variability of temperature. Six hundred early fry stage rohu, Labeo rohita (initial weight 0.097±0.01 g) were equally distributed at four different temperatures (28, 30, 32, 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 was 382±8.01 and 0.88±0.03 respectively, significantly higher than at 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 at 28, 30, 32, 34°C respectively and increased significantly 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, 34°C respectively. Temperature preference of the early fry of rohu was derived from relationship between acclimation temperatures and Q10 values for 28-30°C, 30-32°C, 32- 34°C were 1.94, 2.05, and 1.91 respectively. The optimum temperature range for growth was 30-32°C and Q10 value was 32-34°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 temperatures.