鳊鱼和宽鳍鱲幼鱼流速选择与运动能量代谢特征的关联

Flow velocity selection and its relationship to locomotive energetic metabolism in Chinese bream( Parabramis pekinensis) and pale chub( Zacco platypus)

为考察喜好激流环境的宽鳍鱲(Zacco platypus)和喜好缓流环境的鳊鱼(Parabramis pekinensis)的最适游泳速度和流速选择的关联以及运动能量代谢特征对流速选择的影响,在(25±0.5)℃条件下将实验鱼(n=13×2)单尾分别置于梯度流速选择仪(设定流速范围为18.6—102.7 cm/s,等距离划分为5个流速区域)中获取视频资料,采用Ethovision XT19软件分析视频资料并计算两种实验鱼在5个流速区域的平均停留时间百分比(P_t)和平均出入频率百分比(Pf);另外,使用游泳代谢仪测定两种实验鱼的临界游泳速度(U_(crit))和不同游泳速度下的运动耗氧率(M_(O2)),并计算出不同速度下单位位移耗能(COT)、最适游泳速度(U_(opt))、静止耗氧率(RMR)和净单位位移耗能(COTnet)。结果显示:鳊鱼的U_(crit)和RMR均显著小于宽鳍鱲(P<0.05),但二者的最大耗氧率(MMR)无显著差异;随游泳速度的增加,两种实验鱼的M_(O2)均显著上升,尽管在较低游泳速度下,鳊鱼的M_(O2)和COT均小于宽鳍鱲,但在高游泳速度下则相反;两种实验鱼的U_(opt)分别为(6.20±1.29)体长(BL)/s和(11.56±1.57)BL/s,鳊鱼显著小于宽鳍鱲;两种实验鱼的COTnet随着游泳速度增加差异逐渐增大,鳊鱼显著高于宽鳍鱲(P<0.05);两种实验鱼在最低流速区域(18.6—23.8 cm/s)的P_t和Pf显著大于其他速度区域(P<0.05),由此可见两种实验鱼的偏好游泳速度(U_(perf))等于或小于(18.6—23.8 cm/s),然而鳊鱼在最低速度区域P_t和Pf均显著大于且在较高速度区域的P_t和Pf则均显著小于宽鳍鱲(P<0.05)。结果表明:有别于过往研究的是两种实验鱼的U_(perf)均与U_(opt)偏离;在激流环境中生存的宽鳍鱲更加偏好较高的水流速度,生境水流对实验鱼的水流速度选择特征存在显著影响,这种影响的主要能量学机制与鱼类的运动能量效率有关。

Several measures have been developed to quantify swimming performance to understand various aspects of ecology and behaviour in fish species, as well as to help design functional applications for fishways and aquaculture. The aim of this study was （ 1 ） to explore the relevance between the optimal swimming speed （ Uopt ） and preferred swimming speed （Upref） , and （2） to investigate the relationship between locomotive energetic metabolism and flow velocity selection in aquatic organisms. For the study, we selected pale chub （Zacco platypus）, a fish species typically occurring in riptide habitats, and Chinese bream （ Parabramis pekinensis ） , a fish species inhabiting lentic ecosystems, as experimental models. In experiment I, both fish species were videotaped individually （N= 13 for each species） in a self-made device to determine Upref. The device consisted of a 1-m-long conical raceway with water speed ranging from 102.7 to 18.6 cm/s and water temperature of （25 ± 0.5）℃. The raceway was artificially divided into 5 flow velocity intervals with equal length （i.e. 20 cm each intervals）. The videos were then analyzed by Ethovision XT19. The percentage of time stayed in each flow velocity interval during the whole video period （P,） and frequency of crossing each intervals （P1） were calculated. In experiment II, the critical swimming speed （ Ucrit ） and swimming metabolic rate （Mo2） were measured at different swimming speeds. Resting metabolic rate （ RMR）, cost of transport （ COT）, net cost of transport （ COTnet ）, and Uopt were calculated for each species. The experimental results were as follows ： （ 1 ） both Ucrit and RMR of Chinese bream were significantly higher than those of pale chub （P〈0.05）, whereas maximum metabolic rate （MMR） showed no significant difference between two fish species. （2） Mo2 increased significantly while COT decreased significantly with swimming speed in both fish species. Furthermore, Chinese bream showed lower Mot and COT values within low swimming speed range while it showed higher Mo2 and COT values within high swimming speed range compared to those of pale chub. （5） COTnet of the two fish species increased with swimming speed, and the difference of COT.o,（pale chub showed lower COTnet than Chinese bream） between the two species gradually increased with the increase in swimming speed （P〈0.05）. （4） Uopt of Chinese bream （ （6.20± 1.29） body length （BL）/s） was significantly higher than that of pale chub （ （ 11.56± 1.57） BL/s）. （5） P, in the area of the minimum velocity interval （18.6--23.8 cm/s） in the present study was significantly larger than those in other areas （P〈0.05）, suggesting that Uporf of both fish species was lower than （or equal to） the range 18.6--23.8 cm/s. However, Pt of Chinese bream in the area of the minimum velocity interval was significantly larger than that of the pale chub （ P〈0.05 ）, whereas P1 of Chinese bream in the areas of high velocity intervals was significantly lower than that of the pale chub. The present study demonstrated that Upot and Uopt were irrelevant in both fish species. Pale chub, which typically occur in torrent habitats, preferred higher flow velocity ; this may be related to its locomotive energetic metabolism such as high Uopt and Ucrit and low COTnet, when compared to Chinese bream.