Abstract Modern ethohydraulics is the study of the behavioral responses of swimming fish to flow fields. However, the exact drag forces experienced by fish remain poorly studied; this information is required to obtain a better understanding of the behavioral responses of fish and their current resistance strategies. We measured near-ground frontal drag forces on preserved individuals of three benthic fish species, round goby (Neogobius melanstomus), gudgeon (Gobio gobio) and bullhead (Cottus gobio), in a flow channel. The forces were compared to acoustic Doppler velocity (ADV) measurements and fish tracking data based on video observations of live fish in the flow channel. Overall, we observed drag coefficients (CD) of ∼10−3 at Reynolds numbers ∼105. The frontal drag forces acting on preserved fish with non-spread fins ranged from -1.96 mN*g-1 (force per fish wet weight, velocity 0.55 m*s-1) to 11.01 mN*g-1 (velocity 0.85 m*s-1). Spreading the fins strongly increased the drag forces for bullhead and round goby. In contrast, the drag forces were similar for gudgeon with spread fins and all fish with non-spread fins. Video tracking revealed no clear relationship between the position of the fish in the flow field and the forces experienced by the preserved fish at these positions. Collectively, these results suggest that i) the differences in frontal drag forces between species are small in homogenous flow, ii) individuals chose their position in the flow field based on factors other than the drag forces experienced, and iii) whether fins are spread or non-spread is an essential quality that modulates species-specific differences. The methodology and results of this study will enable integration of flow measurements, fish behavior and force measurements and inform ethohydraulics research. More advanced force measurements will lead to a detailed understanding of the current resistance strategies of benthic fish and improve the design of fish passes.

中文翻译：

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三种底栖鱼类的流场诱导阻力与游泳行为

摘要 现代水力学是研究游泳鱼对流场的行为反应。然而，鱼所经历的确切阻力仍然缺乏研究。需要这些信息才能更好地了解鱼类的行为反应及其当前的抵抗策略。我们在流动通道中测量了三种底栖鱼类，圆形虾虎鱼 (Neogobius melanstomus)、gudgeon (Gobio gobio) 和牛头鱼 (Cottus gobio) 的保存个体的近地正面阻力。根据对流道中活鱼的视频观察，将这些力与声学多普勒速度 (ADV) 测量值和鱼跟踪数据进行了比较。总体而言，我们在雷诺数 105 处观察到阻力系数 (CD) 为 10-3。作用于未展开鳍的腌制鱼的正面阻力范围为 -1。96 mN*g-1（每条鱼湿重的力，速度 0.55 m*s-1）到 11.01 mN*g-1（速度 0.85 m*s-1）。展开鳍强烈增加了牛头鱼和圆形虾虎鱼的阻力。相比之下，带有展开鳍的鱼和所有具有非展开鳍的鱼的阻力相似。视频跟踪显示鱼在流场中的位置与保存在这些位置的鱼所承受的力之间没有明确的关系。总的来说，这些结果表明 i) 在同质流中，物种之间的正面阻力差异很小，ii) 个体根据所经历的阻力以外的因素选择他们在流场中的位置，以及 iii) 鳍是展开还是展开非传播是调节物种特异性差异的基本品质。这项研究的方法和结果将能够整合流量测量、鱼类行为和力测量，并为人类水力学研究提供信息。更先进的力测量将导致详细了解底栖鱼类当前的阻力策略并改进鱼道的设计。