Data from: Field swimming behavior in largemouth bass deviates from predictions based on economy and propulsive efficiency

Locomotion is energetically expensive. This may create selection pressures that favor economical locomotor strategies, such as adoption of low cost speeds and efficient propulsive movements. For swimming fish the energy expended to travel a unit distance, or cost of transport (COT), has a U-shaped relationship to speed. The relationship between propulsive kinematics and speed summarized by the Strouhal number (St = fA/U, where f is tail beat frequency, A is tail tip amplitude in m and U is swimming speed in m s-1) allows for maximal propulsive efficiency where 0.2运动的能量代谢成本高昂。此类生理成本可产生选择压力，推动生物演化出更经济的运动策略，例如采用低能耗运动速率与高效推进动作。对于游泳鱼类而言，其行进单位距离的能量消耗，即运输成本（cost of transport, COT），与游泳速度呈U型相关关系。推进运动学特征与运动速度之间的关联可通过斯特劳哈尔数（Strouhal number，St = fA/U，其中f为尾鳍拍打频率，A为尾尖摆幅（单位：m），U为游泳速度（单位：m·s⁻¹））进行概括，可实现最大推进效率，此时斯特劳哈尔数满足0.2