Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark
Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA 92697, USA.
J Exp Biol. 2018 Jun 12;221(Pt 11):jeb168773. doi: 10.1242/jeb.168773.
Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch, (a labriform swimmer), were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with particle image velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rate of the swimming fish increased with swimming speed and pectoral fin beat frequency in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (versus low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high-turbulence compared with low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behaviour and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.
鱼类游泳的能量学通常在实验室环境中进行测量，实验室环境试图将湍流最小化，尽管在自然环境中湍流很常见。为了测试闪光鲷（一种平鳍鱼类）的游泳能量学和运动学是否受到湍流的影响，在游泳呼吸测量仪中构建了两种流动条件。通过使用带有流动整流器和细网格的常见游泳呼吸测量仪设置来创建低湍流流动，以最小化速度波动。通过允许大的速度波动在没有流动整流器或细网格的情况下持续存在，创建了高湍流流动条件。使用粒子图像测速法对这两种条件进行了测试，以确认在整个平均流速范围内湍流特性有显著差异。在两种流动条件下，游泳鱼的耗氧量均随游泳速度和胸鳍拍打频率的增加而增加。较高的湍流也会导致游泳个体在中高速时的位置变异性更大（与低湍流流动相比）。令人惊讶的是，与低湍流流动相比，鱼类在中高速时在高湍流中消耗的氧气更少。游泳运动学的同步测量表明，这些耗氧量的减少不能用特定的已知适应流动的行为来解释，如卡门步态或诱导向流。因此，在高湍流流动中的鱼类可能会利用湍流能量随时间的高度可变性。这些结果表明，在直线流动中（典型的标准游泳呼吸测量仪）实验室测量的游泳行为和能量学可能与更具湍流的半自然流动条件不同。
