Thermal Tolerance And Comparison Of Juvenile Silurus Meridionalis Chen, Pelteobagrus Vachelli Richardson And Spinibarbus Sinensis Bleeker

Thermal tolerance of juvenile Spinibarbus sinensis Bleeker(5.21±0.38 g), Pelteobagrus vachelli Richardson(7.03±0.20 g) and Silurus meridionalis Chen (16.9±0.3 g),which belonged to different species and lived in sympatric water of the Three Gorges reservoir, was evaluated in terms of critical thermal maximum (CTmax), critical thermal minimum (CTmin), lethal thermal maximum (LTmax) and lethal thermal minimum (LTmin), after acclimated at different acclimation temperatures.The aim of this study was to investigate the effect of the acclimation temperature on the thermal tolerance of juvenile S. sinensis, P. vachelli and S. meridionalis and to draw comparisons. To predict the adaptation of changes in water temperature in the reservoir area of these fish.The main results:1. At different acclimation temperatures (5, 10, 15, 20, 25, 30 and 35℃) , the maximum critical temperature (CTmax) and the minimum critical temperature (CTmin) of juvenile S. sinensis were from 33.74℃to 40.81℃and 0.98℃to 10.58℃, separately. Maximum lethal temperature (LTmax) and minimum lethal temperature (LTmin) from 35.16℃to 41.01℃and 0.73℃to 9.89℃, separately. What can be seen is that the maximum critical temperature and the maximum lethal temperature increased as the acclimation temperature increased; the minimum critical temperature and the minimum lethal temperature decreased as the acclimation temperature decreased. The thermal tolerance amplitude were 32.76℃,32.06℃,32.77℃,32.66℃,32.81℃,30.11℃,30.23℃at each acclimation groups, respectively. As the acclimation temperature range was 30℃, the acclimation response ratios were 0.24 (5℃~ 35℃↑) and 0.32 (35℃~ 5℃↓); the area of thermal polygon over the range from 5 to 35℃acclimation temperatures of the juvenile S. sinensis was calculated as 959.5℃2.2. At different acclimation temperatures (5, 10, 15, 20, 25, 30 and 35℃) , the maximum critical temperature (CTmax) and the maximum lethal temperature (LTmax) of juvenile P. vachelli were from 30.02℃to 40.68℃and 30.43℃to 40.89℃, separately ,increased with increasing acclimation temperatures, whereas the minimum critical temperature (CTmin) minimum lethal temperature (LTmin) from 0.54℃to 9.60℃and <0℃to 8.62℃,decreased with decreasing acclimation temperatures. The thermal tolerance amplitude were 29.48℃,28.34℃,30.41℃,30.88℃,32.87℃,29.86℃,31.08℃at each acclimation temperature. As the acclimation temperature range was 30℃, the acclimation response ratios were 0.36 (5℃~ 35℃↑) and 0.30 (35℃~ 5℃↓); the area of thermal polygon over the range from 5 to 35℃acclimation temperatures of the juvenile P. vachelli was calculated as 913.2℃2。3. Thermal tolerance of the juvenile S. meridionalis was evaluated interms of critical thermal maximum (CTmax), critical thermal minimum (CTmin), lethal thermal maximum (LTmax) and lethal thermal minimum (LTmin), after acclimated at 10, 20 and 30℃for 2 weeks. CTmax (34.13, 38.22 and 39.41℃) and LTmax (34.84, 38.63 and 39.53℃) increased with increasing acclimation temperatures, whereas CTmin (4.88, 5.90 and 9.80℃) and LTmin (4.12, 5.03 and 8.29℃) decreased with decreasing acclimation temperatures. The thermal tolerance amplitude were 29.25℃, 32.32℃and 29.61℃at 10, 20 and 30℃acclimation groups, respectively. When acclimation temperatures were between 10℃and 20℃. the acclimation response ratios (ARR) were 0.41 and 0.12 with increasing or decreasing temperatures. When acclimation temperatures were between 20℃and 30℃the acclimation response ratios (ARR) were 0.10 and 0.39 with increasing or decreasing temperatures. The area of thermal polygon over the range from 10 to 30℃acclimation temperatures of the juvenile S. meridionalis was calculated as 617.5℃2.The indications of this study:1. The changing trends of thermal tolerance indicators (CTmax, CTmin, LTmax and LTmin)for three kinds of fish at its entire range of acclimation temperatures are consistent, increased with increasing acclimation temperatures and decreased with decreasing acclimation temperatures. This also proves that the thermal tolerance of juvenile S. sinensis, P. vachelli and S. meridionalis largely depend on acclimation temperature. 2. The juvenile S. sinensis, P. vachelli and S.. meridionalis have wide temperature tolerance characteristics like other warm water fish. It also shows that some thermal tolerance characteristics are similar for fishs living in sympatric water.3. Hot tolerance of juvenile S. sinensis is the strongest, followed by juveniles S.. meridionalis, juvenile P. vachelli is the weakest; Cool tolerance of juvenile P. vachelli is the strongest , juvenile S. sinensis second, the weakest is juvenile S. meridionalis. It also shows that some thermal tolerance characteristics are different because the life history strategy,although these fishs living in sympatric water .4. Temperature variations of Three Gorges reservoir caused by possible temperature stratification at a specific period of time will not impact juvenile S. sinensis, P. vachelli and S. meridionalis greatly on their temperature tolerance characteristics analysis. But other factors'changes caused by temperature change may exert an influence on the distribution, growth, development, population structure and density of juvenile fish S. sinensis, P. vachelli and S. meridionalis.