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Updated: Apr 5, 2026

Swimming Performance Assessment in Fishes
Published on: May 20, 2011
Morphology and energetics of the wake behind a continuously swimming crucian carp at different flow velocities
Yiqun Hou1, Xiang Wang2, Feifei He3
1Key Laboratory of Ecological Impacts of Hydraulic-Projects and Restoration of Aquatic Ecosystem of Ministry of Water Resources, Institute of Hydroecology, Ministry of Water Resources and Chinese Academy of Sciences, Innovation Team of the Changjiang Water Resources Commission for River and Lake Ecosystem Restoration Key Technology, Wuhan, 430079, China.
Abstract:
Understanding the hydrodynamic principles underlying fish swimming efficiency is critical for optimizing fishway design and improving habitat restoration. Wake morphology and energetics of continuously swimming crucian carp were examined across flow velocities in a Brett-type swimming tunnel and analyzed using the velocity gradient method. High-speed video captured swimming behavior and two-dimensional particle image velocimetry were used to visualize the flow field generated by the fish. The critical swimming speed (Ucrit) of crucian carp was 0.85 m/s and wake vortices were observed across flow velocity gradients ranging from 0.15 to 1.2 m/s. The wake beat frequency and vorticity of the wake increasing linearly with flow velocity. Hydrodynamic efficiency of the wake vortex energy ranged from 62 to 84%. Significant changes in tailbeat amplitude, head beat amplitude, and stride length were observed near (70-88%) Ucrit (0.60-0.75 m/s), when the dimensionless Strouhal number (St) indicates efficient swimming. Thus, we conclude that 70%-88% of Ucrit is the threshold range for efficient swimming and this provides practical guidance for setting flow velocities in fishways and habitat restoration projects that will enhance fish survival.
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