| In this study,the four major Chinese carps with clear demand for downstream migration and the Schizopygopsis Younghusbandi with short distance downstream migration demand were selected as the research objects.First of all,the experimental study of "fish downstream behavior quantification and effect evaluation under different setting angles of fishing net" was carried out on the four major fishes,among which the setting angles of fishing net were 10 o,20o and 30 o.By quantifying the downstream behavior of the four carps,the difference in behavior was analyzed,and the effect of fishing net guiding from different angles was evaluated.As for the experimental study,the following conclusions are mainly drawn:1)The downstream time of same fish under different operating conditions with different setting angles is significantly different(P<0.05).Under the same angle working condition,the downstream time of different experimental fish also has significant difference(P<0.05),which indicates that different species of fish have different sensitivity to the fishing net.In terms of the factor analysis affecting the downstream time,the two-factor analysis on the downstream time after the species of experimental fish,angle design and interaction between the two shows that the species of experimental fish and the interaction between the two will significantly affect the downstream time.Pure Angle design has no significant effect on downstream time(P>0.1).Therefore,the downstream time can be weakened to evaluate the guiding effect of the fishing net.2)By analyzing the net attaching behaviors of experimental fishes represented by bighead juveniles,it was found that the net attaching times were less and the net attaching time was shorter at different angles.3)By analyzing the escape behavior of the fish when they encounter the fishnet,it was found that there is no significant difference in the escape times and escape time of the bighead juveniles under different working conditions(P>0.1).The escape times of the silver carp and grass carp juveniles under 10 o working conditions are significantly more than those of the other two working conditions(P<0.05).Therefore,from the perspective of escape behavior,it is recommended to select 20 o or 30 o operating conditions.4)By analyzing the active and passive downstream condition of the four major fishes,it can be seen that the active downstream rate of the four major fishes is the highest under 30 o condition,and the mean value variance reaches(66.99±34.44)%.At the same time,the passive downstream rate of the four major fishes is the lowest under this condition,which is(0.46±0.79)%.Therefore,the setting angle of the fishing net recommended from the active and passive downstream state is 30 o.In conclusion,the quantitative analysis and difference analysis of each downstream behavior were carried out,and the evaluation of the fish guiding effect of the fishing net was conducted.It was found that the fish guiding effect could be better if the angle setting of 30 o in the vertical direction of the water flow was adopted when the four fishes were downstream to deal with the fishing net.In the process of fish downstream,in addition to dealing with physical migration obstacles,fish will also encounter flow obstacles such as accelerating flow.Given the lab early has rich research on four major fish downward to accelerating flow accumulation,to explore the behavior responding to corresponding downstream migratory obstacle of fish with different downstream migratory demand from different river,the Schizopygopsis Younghusbandi from the yarlung zangbo river basin was selected as the research object,the velocity range were 58.91 ~ 81.19 cm/s,63.85 ~ 90.52 cm/s,71.29 ~ 116.45 cm/s,and the acceleration were 0.405m·s-1/m、0.485 m·s-1/m、0.821m·s-1/m respectively.Analyzing the corresponding hydraulic conditions when characteristic of the downstream migration behavior occurred of Schizopygopsis Younghusbandi.The experimental results can provide hydraulic design parameters for the fish downstream migratory projects.As for the experimental study,the following conclusions are mainly drawn:1)Under the condition of low flow rate,most of the experimental fish swim close to the side wall,and avoidance behavior mostly occurs in the side wall,while some avoidance behavior occurs after they go downstream to the accelerating flow.Fish avoidance points in middle velocity condition were relatively discrete distribution,high flow velocity condition experiment fish avoidance points are mainly distributed in the region of the accelerating flow downstream2)There were significant differences in the relative and absolute swimming velocities of the experimental fish under different working conditions(P<0.05),3)The rate of successful escape of experimental fish was the highest at medium velocity.In terms of downstream mode,the experimental fish showed active,passive and conversing to the direction of the current under the condition of low flow rate,while the experimental fish only showed active and passive downstream behavior under the condition of medium flow rate and high flow rate,and the passive downstream ratio was higher than the active downstream ratio.4)Analysis of accelerating hydrodynamic characteristics corresponding to the characteristic behavior of Schizopygopsis Younghusbandi.The corresponding hydraulic conditions were extracted when the escape behavior of the experimental fish occurred,and it was found that the escape behavior of the experimental fish occurred within the flow velocity range of 60 ~ 70cm/s,and the corresponding turbulent kinetic energy was mainly distributed in the range of 20 ~ 30cm2/s2,and the flow acceleration was mainly distributed in the range of 0.6 ~ 1.2m/s2.Based on the above " The typical downstream migration behavior and the hydraulic characteristics of five kinds of fish with different downstream migratory demand" experiment,the paper in the Jin Sha river middle reaches of the Long Kai Kou hydropower project as an example,put forward the water conservancy hub project for fish downstream measures design idea,the building is placed above the irrigation water inlet block nets canals,block nets set angle by chapter 3 of the experimental results,which is 30 o,channel flow field within the design need to consider the downstream fish preferences of flow speed and avoid the hydraulics characteristics of escape behavior,Based on the previous research accumulation in our laboratory and my own experimental research,the flow rate in the canal is set as 0.3m/s.In conclusion,this study which is about the " the typical downstream migration behavior and the hydraulic characteristics of five kinds of fish with different downstream migratory demand " launched two fish ecology experiment,and apply the results to the Long Kai Kou downstream measures in the design of water conservancy project,which makes the results of the study has a certain practical engineering value. |
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