Ecohydraulics Study On Spawning Behavior Of Grass Carp Of The Four Major Chinese Carps In The Middle Reach Of The Yangtze River

Water conservancy project construction has a huge social and economic bene fits in flood control,irrigation,power generation,but also changed the downstream hydrological situation at the same time,which has a significant impact on the ecological environment of the river.The four major Chinese carps are important commercial fishes in China which mainly live in the Yangtze River.But the regulation of large reservoirs such as Three Gorges Project and Gezhouba Project in the middle reach of the Yangtze River changed hydrological conditions of river,which blocked the migration route and destroyed suitable spawning environment seriously,the amount of The four major Chinese carps resources has been severely attenuate.In order to reveal the suitable flow conditions for fish spawning,promote the four major Chinese carps spawning benefits and maintain the sustainable development of fisheries resources in the middle reach of Yangtze River,it has great significance for exploring the spawning behavior of the four major Chinese carps.This article selected grass carp fish in The four major Chinese carps as the research object,combined the ecological hydraulics and fish behavior,designs of a large-scale tank experiments,structured diversity and appropriate velocity of flow environment and suitable velocity,revealed the quantitative relationship between the parent fish spawning and velocity.Meanwhile,based on the field monitoring data of The four major Chinese carps spawning grounds in Yichang to Yangjiazui in the middle reach of Yangtze river,this article established the response of the fish spawning behavior to the key hydrodynamic factors,and put forward the inducing velocity range and suitable velocity range of the parent fish spawning,which through the numerical simulation and statistical analysis.The results of laboratory experiment and field monitoring data was confirmed with each other,and the main conclusions were as follows:(1)Experiment study on the spawning behavior of grass carp.Based on the experiment of large water channel for fish spawning,choosing grass carp as experimental object,the paper analyzed the rate of spawning fish under different flow rate stimulations.The experimental results show that velocity is the key factor of fish spawning,trigger flow rate was 1.40±0.05 m/s and appropriate flow rate was 1.60±0.05 m/s.(2)Inquire into the spawning location of The four major Chinese carps in the middle reach of the Yangtze river.Three-dimensional model of Delft-3D was applied to simulate the flow dynamics from Yichang to Yangjiazui.Collet the spawning data of The four major Chinese carps from May to July of the year 2014~2016.According to the spawning time of the four major Chinese carps’ eggs captured,the drifting distance of fish eggs and the location where the four major Chinese carps spawning could be deduced.The results showed that the location of the key spawning ground was located in the river segment of Aijiazhen to Honghuatao,which was consistent with the historical survey results.(3)Analysis of the suitable conditions for The four major Chinese carps spawning in the middle reach of the Yangtze river.Based on the spawning data of the four major Chinese carps spawning period from 2014 to 2016,the response of the fish spawning behavior to the key hydrodynamic factors was established by statistical analysis of the velocity and velocity variability of spawning position.The results showed that the four major Chinese carps’ spawning appropriate inducing velocity ranged from 1.11 to 1.49 m/s.The suitable velocity ranged from 1.40 to 1.60 m/s.The suitable velocity variability ranged from 0.04 to 0.12(m/s)/d.The results of this study were verified with the laboratory results which can provide theoretical basis and technical reference in inferencing four major Chinese carps spawning ground,ecological rehabilitation and reservoir biological regulation.