不同温度下重复疲劳运动对鲢幼鱼游泳能力及代谢率的影响

Effects of Fatigue and Temperature on the Swimming Performance and Metabolic Rate of Juvenile Silver Carp (Hypophthalmichthys molitrix)

在自行设计的鱼类游泳能力测定装置中,采用流速递增法,测定了不同温度(10、15、20、25℃)条件下鲢(Hypophthalmichthys molitrix)幼鱼2次疲劳运动过程中临界游泳速度和耗氧率的变化,探究重复疲劳运动对鲢幼鱼游泳能力和活动代谢率的影响。结果表明,在10~25℃温度范围内,鲢幼鱼临界游泳速度随温度升高而呈线性增加(U_(crit,1)=3.52+0.14T,R^2=0.98,P<0.05;U_(crit,2)=3.33+0.09T,R^2=0.97,P<0.05),重复运动后的临界游泳速度明显小于第1次。运动最大耗氧量(MMR)和标准代谢率(SMR)均随温度升高而增加,且第1次测试的耗氧率显著高于第2次;运动后过量耗氧率(Excess post-exercise oxygen consumption,EPOC)随着温度升高而增加,与温度相关性显著(P=0.024);第2次测试疲劳后EPOC较第1次低,疲劳运动对EPOC影响不显著(P=0.36);表明适宜温度范围内,温度对游泳能力和活动代谢具有促进作用,疲劳运动对鱼类游泳能力和活动代谢不利,有一定的抑制作用。

Hydropower projects fragment natural river habitat and alter the downstream hydrologic regime,leading to serious declines,or even extinction,of wild fish populations. Silver carp（ Hypophthalmichthys molitrix）,a common semi-migratory fish species inhabiting in the Yangtze River basin,is dramatically declining in recent years due to dam construction,over-fishing,and pollution. To better understand the swimming performance and metabolic demands of silver carp during exhaustive exercise and to provide basic data for the optimizing fish passage design,we conducted a laboratory investigation of the changes in critical swimming speed and metabolic rate of juvenile silver carp using a stepped-velocity test. Two trials were carried out in a flume-type respirometer at four temperatures（ 10,15,20,25℃） and the critical swimming speed was determined to study the effect of repeated fatigue swimming. Oxygen consumption rates during the swimming and recovery phases were measured. Based on the results,the effect of repeated fatigue on swimming ability and active metabolic rate of juvenile silver carp were analyzed.The test fish were randomly divided into four water tanks with ten fish in each group and acclimated for 1- 2 weeks at the designated water temperature. Fish were then transferred to the respirometer two hours before the test at a low velocity（ 0. 06 m/s） to acclimate to the swim chamber and the velocity was increased to 60% of the estimated critical swimming speed（ Ucrit） over 5 min and the flow velocity was then increased in increments of 0. 15 Ucritat20 min. intervals. The DO was recorded every 5 min and the test was complete when the test fish was exhausted.After a 60 min resting period,another test was carried out under the same conditions. After testing,the length and weight of the silver carp was measured. Results show that Ucritincreased linearly with water temperature in the experimental range（ 10- 25℃） in both trials： Ucrit,1= 3. 52 ＋ 0. 14T（ R2= 0. 98,P〈 0. 05）; Ucrit,2= 3. 33 ＋ 0. 09T（ R2= 0. 97,P〈 0. 05）. The Ucritof the juvenile silver carp in the second trial was clearly lower than in the first trial,but the difference was significant only at 10℃. The maximum metabolic rate（ MMR） and standard metabolic rate（ SMR） both increased with water temperature,but the MMR and SMR during the first trial were significantly higher than those during the second trial. The excess post-exercise oxygen consumption（ EPOC） also increased with temperature and there was significant correlation（ P = 0. 024）. The EPOC after the second trial was lower than that for the first trial,but the different was not significant,indicating that fatigue did not significantly impact EPOC（ P = 0. 36）. In conclusion,higher temperature increases the Ucritand MMR of silver carps over range of temperature in this study. Fatigue affects swimming ability and metabolic activity to some degree,but fatigue recovery is enhanced. Our results will provide reference data for the design of an effective fish passage for silver carp.