Harvard University, Cambridge, United States.
Elife. 2023 Feb 6;12:e81392. doi: 10.7554/eLife.81392.
Schooling in fish is linked to a number of factors such as increased foraging success, predator avoidance, and social interactions. In addition, a prevailing hypothesis is that swimming in groups provides energetic benefits through hydrodynamic interactions. Thrust wakes are frequently occurring flow structures in fish schools as they are shed behind swimming fish. Despite increased flow speeds in these wakes, recent modeling work has suggested that swimming directly in-line behind an individual may lead to increased efficiency. However, only limited data are available on live fish interacting with thrust wakes. Here we designed a controlled experiment in which brook trout, , interact with thrust wakes generated by a robotic mechanism that produces a fish-like wake. We show that trout swim in thrust wakes, reduce their tail-beat frequencies, and synchronize with the robotic flapping mechanism. Our flow and pressure field analysis revealed that the trout are interacting with oncoming vortices and that they exhibit reduced pressure drag at the head compared to swimming in isolation. Together, these experiments suggest that trout swim energetically more efficiently in thrust wakes and support the hypothesis that swimming in the wake of one another is an advantageous strategy to save energy in a school.
鱼类的学习能力与其觅食成功率、逃避捕食者和社交互动等多种因素有关。此外，一个流行的假设是，群体游动通过水动力相互作用提供了能量效益。在鱼类群体中，尾流是经常出现的流动结构，它们是在游动的鱼类后面产生的。尽管在这些尾流中流动速度加快，但最近的建模工作表明，直接在个体后面游动可能会提高效率。然而，关于活体鱼与推力尾流相互作用的可用数据有限。在这里，我们设计了一个受控实验，其中包括虹鳟鱼与由产生类似鱼类尾流的机器人机构产生的推力尾流相互作用。我们发现，鳟鱼会在推力尾流中游动，减少它们的尾部拍打频率，并与机器人的拍打机构同步。我们的流场和压力场分析表明，鳟鱼与迎面而来的漩涡相互作用，并且与单独游动相比，它们的头部压力阻力降低。总的来说，这些实验表明，鳟鱼在推力尾流中更有效地游动，支持了彼此在尾流中游动是一种节省群体游动能量的优势策略的假设。
