Suitability analysis of three dimensional hydraulic factors for spawning habitat of Chinese Sturgeon (Acipenser sinensis)

This study employs a three-dimensional hydrodynamic model to analyze the spatial and temporal characteristics of stream flows at spawning sites of Chinese Sturgeon. The overarching goal here is to identify the suitable flow conditions for the sturgeon's reproduction success. Such information will provide better design criteria for habitat management. The results showed that, while flow depth and velocity were determined by the water discharge, the intensity of vorticity was highly dependent upon the local geomorphological features. The velocity and vorticity exhibited much larger magnitudes and higher spatial variability at the location immediately downstream of the dam and between the spur dikes, as compared to other places. More specifically, the mean velocity and vorticity magnitudes there were reported as 2.4 m/s and 11 m²/s, respectively. Such an intense flow condition represented an appropriate spawning cue to the Chinese Sturgeon. Since the spawning activities usually took place near the water surface, this study distinguished the hydrodynamics of the flow within the upper layer from those in the intermediate and bottom layers. The mean velocity and horizontal vorticity manifested a similar distribution among the three different layers, except that the upper layer always had a larger intensity than the lower parts of the flow. The vertical vorticity, on the contrary, attained peak values in the intermediate layer exceeding the intensities observed in the upper and bottom layers. This result indicated the high spatial variability of hydrodynamics that could change with flow depth. Overall, the pertinent flow properties at the upper, intermediate, and the bottom layers may contribute to spawning success in different ways. It is reasonable to expect that the Chinese sturgeon will select the sites that are more likely to meet their special needs in the spawning processes.