Abstract:Chinese sturgeon, a kind of migration or semi-migration fish growing up in coastal water and entering into rivers after sexual maturity, is one of Class I state protection animals. The construction of the Gezhouba dam blocked its migration route to the upstream of the Jinshajiang River，as a result，Chinese sturgeon established a new spawning ground in the less than 7 km long mainstream of the Yangtze River below the Gezhouba. The applicability of the Delft 3D-Flow model to simulation of the flow field of the spawning ground was verified by observed data. On the basis of the simulated flow field of the spawning ground, the computational method of the horizontal mean vorticity was proposed and then employed to compute its distribution throughout the spawning ground. The computed results indicated that horizontal mean vorticity varies between 1.184×10-3-5.413×10-3s-1for the whole spawning ground and 1.38×10-3-1.64×10-3s-1 for the patches with a high density of Chinese sturgeon eggs. This revealed that the spawning of Chinese sturgeon has a preference for a specific range of vorticity, which could benefit the increase in fertilization rate of Chinese sturgeon eggs and the protection of its zygotes. This paper could provide references for protecting the hydraulic environment required by the spawning ground of Chinese sturgeon.