Effects of Temperature and Water Velocity on the Respiratory Metabolism and behavior of Phoxinus lagowskii Dybowskii

Here,we aimed to determine the effects of water temperature and flow velocity on the respiratory metabolism and behavior of one-and two-year-old Phoxinus lagowskii Dybowski by using experimental ecological methods.The results showed that yearling and two-year-old P.lagowskii did not feed and showed slow growth at4[degrees]C.With an increase in water temperature,fish feeding and growth improved.However,at 28[degrees]C,the feeding activities of P.lagowskii reduced,and significant weight loss was noted; the fish began to die after 7d,and the death rate increased gradually.The oxygen consumption rate increased at a flow velocity of 16cm/s and 18cm/s,as well as with increasing temperature from 4[degrees]Cto 28[degrees]C,showing a typical exponential growth trend.The equation was Y=aeb x(R2 0.90).Regardless of the temperature changes,yearling and two-year-old P.lagowskii showed no significant differences in their state,i.e.,the number of times they wagged their tail,lied prone at the bottom,and had a disorganized head position,at a flow rate of 8cm/s and 10cm/s.In contrast,at the flow rate of 16cm/s and18cm/s,the oxygen consumption rate declined with an increase in temperature from 4[degrees]C to 28 [degrees]C.The oxygenconsumption rate increased with an increase in flow velocity from 8cm/s to 18cm/s at temperatures below 20[degrees]Cin yearling fish or below 24[degrees]Cin two-year-old fish.However,at the flow velocity of 16cm/s,the oxygen consumption rate of yearling fish reached the highest level at temperatures of 24-28[degrees]C,and that of two-year-fish reached the highest level at 28[degrees]C,and decreased thereafter.When the flow velocity was 18cm/s,the tail wagging speed reached the highest level,and yearling fish came closer to the net and stopped swimming after 30 min,whereas two-year-old fish came closer to the net after 1h.The optimum temperature for yearling fish fluctuated within the optimum breeding flow velocity of 12-16cm/s.The minimum area of Q10 was in the range of 16-24[degrees]C when the flow velocity was 12cm/s and 14cm/s,but it was in the range of 16-20[degrees]C and 24-28[degrees]C when the flow velocity was 16cm/s.According to the line graph for flow velocity vs.oxygen consumption rate,the maximum oxygen consumption rate was recorded at 24[degrees]C; the metabolic activity of the fish has reached its limit at this temperature.A lowQ10 value was recorded at 24-28[degrees]C when the flow velocity was 16cm/s,but this temperature was not s