Study On The Correlation Between Hydraulic Characteristics And Fish Behavior In Fishways

The construction of water conservancy project can bring huge economic benefits,but it blocks the connectivity of rivers and changes the hydrological situation,this has an impact on the habitat of fish,resulting in a decrease in the number of fish and a decrease in species richness.In order to protect fish resources and maintain the stability of river ecosystem,the construction of fishway has become a hot issue of ecological water conservancy.Reasonable fishway shape and fish pass way are the key to improve the efficiency of fish pass.Only by combining fishway design with the behavioral characteristics of fish and making the hydraulic characteristics of fishway adapt to the flow capacity of migratory fish,can a better effect of fish pass be achieved.In this paper,grass carp was taken as the research object,and the physical model test was carried out by using the fishway.The correlation between the hydraulic characteristics of fishway and the swimming behavior of fish was studied under five working conditions.The main research contents and conclusions are as follow:(1)By analyzing the flow pattern,the minimum velocity change and velocity distribution in the fishway,revealed the rule of water flow in the fishway.The test shows that under the five working conditions,the turbulence of water flow in the pool is obvious.As the water level in the pool rises continuously,the range of influence of the water flow turbulence zone will continue to shrink to the upstream.The shape of fishway is beneficial to the energy dissipation of the water flow,which effectively reduces the velocity in the middle area of the fishway.(2)Through the observation of the test process and the analysis of the video,the swimming state and the rheotaxis frequency of the fish under each working condition were studied.The study found that there are mainly four swimming states in the test process,which are downstream,countercurrent stillness,countercurrent go-ahead,and countercurrent retreat.The time proportion of each swimming state is different under different working conditions.(3)The fish swimming trajectories in the video is extracted by Logger pro software.It was found that the swimming trajectories of fish under different working conditions were significantly different,and the trajectories were mainly presented as "C" type swimming trajectories and "S" type swimming trajectories.(4)Using Matlab to superimpose the fish swimming trajectory and the velocity cloud map,quantitative analysis of the effect of the velocity on the swimming trajectory of the test fish during the uptracking process.The study shows that the velocity range is between 0.2m/s and 0.4m/s under the conditions of 0-20-0 and 0-25-0,the velocity is suitable to meet the flow requirements of the test fish.Figure [21] Table [3] Reference [102].