Author(s): Senfan Ke; Xiaotao Shi; Zhiying Tu; Yu Wang; Junjun Tan; Yanfen Fang
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Abstract: The relationship between hydraulics of bottom structures and fish swimming behaviour is important for bottom microhabitat restoration. We studied the effects of a vertical geometric object on the critical swimming ability and swimming kinematics of fish. Studies show that critical swimming speeds of different fish species in the flow field with a unique vertical geometric object were increased compared to swimming in free flow, such as critical swimming speeds of juvenile Hypophthalmichthys molitrix with a vertical one-half of cylinder were increased. We investigated the effect of flow speed on the swimming behavior of juvenile Hypophthalmichthys molitrix behind a vertical one-half of cylinder of different diameters (19mm、25mm、32mm and 50mm). Hypophthalmichthys molitrix prefer to swim in influenced field behind a one-half of cylinder with large diameter (32mm and 50mm). Juvenile Hypophthalmichthys molitrix avoided influenced field at low speeds. At intermediate speeds, some fish chose to stay in influenced field, but they were displaced at higher speeds. Video tracking technology showed that fish prefer to form karmen gait kinematics within a certain range of vortex street behind a one-half of cylinder. The relationship between body length and vortex diameter also played a important role in karmen gait kinematics. When the ratio of vortex diameter and a fish body length is close 1, the occurrence of apparent karmen gait bahavior in vortex street is far more frequent than when this ratio is much more than 1.
Year: 2018