Effects of temperature and pH on the oxygen consumption rate, ammonia discharge rate and asphyxiation point of juvenile Eriocheir sinensis

【Objective】To clarify the respiratory and metabolic patterns of juvenile Eriocheir sinensis under different environmental conditions，so as to provide a reference for the optimization of the juvenile crab culture conditions and broodstock breeding.【Method】The effects of different temperatures（10，15，20，25 and 30 ℃）and pH（6.0，7.0，8.0 and 9.0）on the oxygen consumption rate，ammonia discharge rate and asphyxiation point of juvenile E. sinensis of different sizes［L（21.68±3.58 g），M（11.31±0.29 g）and S（5.84±0.33 g）］were investigated in a sealed hydrostatic test.【Result】Temperature and pH had significant effects on the oxygen consumption rate and ammonia excretion rate of E. sinensis（P<0.05，the same below）. With the increase of temperature，the oxygen consumption rate and ammonia discharge rate of juvenile crab showed a rising trend. In the range of 15-30 ℃，the oxygen consumption rate and ammonia discharge rate of juvenile crabs were negatively correlated with body mass，show as S group>M group>L group. With the increase of pH，oxygen consumption performed a trend of decreased first and then increased，while the ammonia discharge rate showed the trend of increased first and then decreased. The oxygen consumption and ammonia excretion rate of crabs were negatively correlated with body mass in pH 6.0-9.0 treatments. Temperature and pH had significant influence on asphyxiation point of crabs. The asphyxiation point at 10 ℃ was significantly higher than that at 15-30 ℃. At pH 6.0-9.0，asphyxiation point performed the trend of decreased first and then increased，and S group was significantly higher than that of M and L groups. In the range of 10-30 ℃，the ammonia quotient and energy metabolic rate of juvenile E. sinensis showed a trend of decreased first and then increased. As pH increased，the ammonia quotient of juvenile crabs tended to increase and then decrease，while the energy metabolic rate tended to decrease and then increase.【Conclusion】Temperature and pH have significant effects on the respiratory and metabolic indexes of juvenile E. sinensis of different sizes. The suitable water temperature for the growth of E. sinensis is 20-25 ℃，and the suitable pH is 8.0. The temperature and pH should not be too high or too low，or it will inflict stress response of juvenile crab，which may affect its normal growth and survival.