亚成体巨须裂腹鱼游泳能力及活动代谢研究

以野生雅鲁藏布江巨须裂腹鱼(Schizothorax macropogon)为对象,通过自制的鱼类游泳实验装置,测定了4个温度(5、10、15和18℃)梯度下亚成体巨须裂腹鱼的临界游泳速度(Ucrit)及流速变化对耗氧率的影响,并通过摄像记录分析了不同游泳速度下的游泳行为。野生亚成体巨须裂腹鱼的临界游速随着温度的变化呈近似线性的递增趋势(P<0.001),4个温度下的绝对临界游速(Ucrit-a)分别为(0.88±0.07)、(1.09±0.07)、(1.24±0.15)和(1.49±0.15)m/s;若以单位时间内游过的体长倍数(BL/s)表示,相对临界游速(Ucrit-r)分别为(3.96±0.21)、(4.4±0.16)、(4.9±0.18)和(5.35±0.14)BL/s。根据不同温度及流速下耗氧率的变化情况,采用非线性拟合得到了4个温度梯度下耗氧率与游泳速度关系的幂函数模型(P<0.05)。模型表明耗氧率随游泳速度的增大而增加,且温度越高耗氧率随游泳速度的变化越显著。4个温度下的速度指数分别为2.4、2.6,2.8及3.1,表明有氧运动的效率随温度升高有所降低。在自然水温条件下(5—9℃),摆尾频率(TBF)与流速的关系呈线性正相关(P<0.001),而运动步长(Ls)的变化与流速没有显著关系,出现由高至低再升高的三个阶段。录像分析表明在流速逐渐增加的过程中,巨须裂腹鱼采用了三种不同的游泳方式,以实现降低能量消耗的目的。研究可为鱼道等过鱼设施的设计提供参考,对数量日益减少的巨须裂腹鱼保护具有较大的意义。

SWIMMING CAPABILITY AND ACTIVITY METABOLISM OF SUBADULT SCHIZOTHORAX MACROPOGON

Schizothorax macropogon(locally known as Huzi Yu),a fish species commonly found in Yaluzangbujiang River,has been declining quickly in recent years.Overfishing is one of the important factors.Hydropower projects that will be built on the river will lead to more significant decline in this species.Building fish passage incorporated into dams together with other fisheries management actions would help maintain local fish fisheries.The swimming capability within specific habitats is likely to be very important data that might be applied to the design of a fishway for S.macropogon.To obtain data that can be applied to the design of a fishway for S.macropogon and other species in the community,a laboratory study on the swimming capability and activity metabolism of wild subadult S.macropogon was conducted in a self-designed apparatus with a video camera system recording their swimming behavior at four acclimation temperature(5,10,15 and 18℃) to reflect seasonal water temperature.Specimens of wild S.macropogon body length(BL) ranging from 20–29 cm,body mass ranging from 176–324 g] were selected and their critical swimming speed(Ucrit),oxygen consumption rate MO2,mgO2/(kg.h)],tail beat frequency(TBF,/min),and stride length(Ls,/beat) were measured and compared during steady swimming at varying flow rates.Both absolute critical swimming speeds(Ucrit-a,m/s) and relative critical swimming speeds(Ucrit-r,BL/s) of subadult S.macropogon increased with the temperature from 5℃ to 18℃ and the relation was approximately linearity(P<0.001).The Ucrit-a were 0.88±0.07,1.09±0.07,1.24±0.15,1.49±0.15 m/s and Ucrit-r were 3.96±0.21,4.4±0.16,4.9±0.18 and 5.35±0.14 BL/s respectively at four different temperatures.The maximum Ucritdid not appear during the temperature from 5℃ to 18℃.Power function models at four different temperatures well described the correlation between MO2 and swimming speed with high correlation coefficient(P<0.05).The derived models showed that MO2 increased with the increase of swimming speed and the increase was more significant as the temperature was higher.The speed exponents of the power fit at four different temperatures were 2.4,2.6,2.8 and 3.1,which means the efficiency of aerobic swimming decreased with the increase of temperature and temperature had a significant effect on swimming performance in subadult S.macropogon.There was a significant positive linear correlation between TBF and swimming speed(P<0.001) at natural water temperature(5–9℃) which was in accord with most reference data,but stride length(Ls) was only weakly correlated with swimming speed and showed three different stages.Recording analyses indicated that S.macropogon depended on caudal fin to generate forward thrust and employed three velocity-dependent swimming modes during the increase of swimming speed: a discontinuous ‘stroke-and-glide’ swimming behavior at low velocity,a continuous swimming behavior as velocity increase and a discontinuous ‘burst-and-glide’ swimming behavior at velocities near Ucrit.This has been shown to be an energy-saving swimming behavior and may benefit the fish by optimizing muscle fiber power output and efficiency.This investigation provided data on the swimming capability and energetics of wild subadult S.macropogon that would add to the basic science required for fishway design and contribute to the protection of this species.