Typical Biological Behavior of Migration and Flow Pattern Creating for Fish Schooling

Hydropower projects undermine the connectivity of rivers, resulting in blocking fish migration, and disrupting fish’s gene exchange, while fish passage is an effective mean of river restoration. During the migration process, fish exhibit different response behaviors to river current and even form an orderly and uniform movement, which is defined as fish schooling. The hydrodynamic characteristics, such as water depth, velocity and turbulence, directly impact the behavior of fish schooling. The most central issue for an effective fish pass facility is to reasonable set up the inlet for fish gathering and attraction. The main difficulty focuses on locating the migratory routes and schooling area. By creating the flow by modifying inlet structure, it is expected to guide the fish found the inlet for positive Rheotaxis.

The biological behavior irritated by flow during migration process is the object of this study. By combining hydraulics, ecological theory, the field investigation, in situ experiment, physical test and numerical modeling methods have been used in this case.It is also introduced ultrasonic detection sonar to detect spatial distribution of target species. The response of target species to hydrodynamic characteristics downstream dam was analyzed subsequently. The Flow-3D software was used to simulate the flow characteristics downstream dam in this study, while the VOF method was used to track free-surface motion. This study well understood the correlation between fish schooling and flow pattern. An optimal design and operation scheme was put forward by optimizing the operation of ecological sluice gate, the flow pattern and diffusion direction.

The study is expected to be resolved evaluation for fish schooling and creating appropriate flow pattern. According to the biological behavior for typical fish in the upper reaches of the Yangtze River, the quantitative description is used for build the response mechanism between hydraulics and biological behavior. The analysis of the suitable habitat hydraulics conditions is also can be given for achieve the final goal, which could be assessing the fish pass facility effect and predict the fish schooling. This research reached a conclusion that the suitable velocity of the fish schooling downstream dam was 0.1-0.25 m/s, the suitable depth of water was 2.4-3.8 m, and the suitable turbulent kinetic energy was 0.00050-0.0015 kg•m²/s².