Study Of Hydrodynamic Characteristics Of Chinese Sturgeon's Spawning Grounds & Transport Characteristics Of Chinese Sturgeon's Eggs

Chinese sturgeon (Aclpenser Sinensis Grdy) is one of the endangered species in China. Their migration channel was blocked by the construction of Gezhouba Dam, so the downstream of Gezhouba Dam becomes their last spawning grounds. In this thesis, field investigation, theoretical analysis, statistics method and numerical simulation are used for studying the hydrodynamic characteristics of Chinese sturgeon's spawning grounds & transport characteristics of Chinese sturgeon's eggs. The major researches in this thesis are listed as follows:(1) This thesis firstly reviews the status of Chinese sturgeon in China and the changes of their spawning grounds. Especially, it summarizes many scholars'research achievements about Chinese sturgeon after the closure of the Gezhouba Dam in 1981.(2) Field investigation of the spawning grounds in the downstream of Gezhouba Dam. Several methods are used in the investigation in 2009; we capture the Chinese sturgeon's eggs, juvenile and other fishes that eat the eggs of Chinese sturgeon; and we use the fish detection equipments and DIDSON (Dual-frequency Identification Sonar) to survey the adult Chinese sturgeon. It shows that Chinese sturgeon has once reproduction behavior in 2009; what's more, we obtain the number of spawning Chinese sturgeon and the area of spawning behavior. Based on those data, the thesis obtains the reasons for Chinese sturgeon to choose different spawning grounds, the first one is the adjustment works in the downstream of Gezhouba Dam, and the other is the joint operations of Three Gorges Dam and Gezhouba Dam.(3) Hydrodynamic characteristics of Chinese sturgeon's spawning grounds. This thesis uses a three dimensional hydrodynamic model and statistics method to study the hydrodynamic characteristics of two different spawning grounds (one was proposed by Wei Qiwei et al., the other was predicted by the field investigation in 2009). It shows that water depth is not a sensitive factor for their reproduction behavior; the velocity ranges in the two spawning grounds have some similarities, especially, most of the two summits are between 1.0 m/s and 1.4 m/s; the size of vortices in two different spawning grounds are less that 1.5×10-3s-1, and the turbulent kinetic energy of the two spawning grounds has some common interval.(4) Weighted usable area (WUA) in the downstream of Gezhouba Dam. Based on the principle of IFIM method, this thesis studies the changes of WUA of Chinese sturgeon spawning grounds under different discharge and different habitat suitability indices. It shows that there are some differences of WUA with different habitat suitability indices, and the ranges of all WUA are between 0.241 km2and 2.768 km2. More importantly, the discharge of Gezhouba Dam is crucial for the maintenance of Chinese sturgeon's WUA in the downstream of Gezhouba Dam.(5) Transport characteristics of Chinese sturgeon's eggs. This thesis initially uses the three dimensional hydrodynamic model and particle tracking method to study the transport characteristics of Chinese sturgeon's eggs. The trajectories of the eggs resealed in different zones are obtained. Further more, this thesis offers a more accurate way to determine the spawning grounds of Chinese sturgeon by probability classifications method for spawning grounds.