Numerical simulation of fish movement behavior for habitat assessment by Eulerian-Eulerian-Habitat-Selection (EEHS) method

The ecological environment of the rivers is affected tremendously by artificial constructions such as hydropower stations and dams. Closure alters hydrological conditions of the downstream area. Accordingly, the habitat conditions of the aquatic animals change negatively. The traditional habitat site models are mostly based on the statistical data that are drawn from the historical observation records. Interactions between aquatic animals' behaviors and environmental issues are often ignored. The Eulerian-Eulerian-Habitat-Selection method (EEHS) in this paper is based on the Boltzmann equation, from the perspective of continuous and momentum theories, with the influences of other environmental factors such as water depth, temperature, substrate and sediment concentration. The movement procedure and distribution of the objects can be obtained by solving the deformed Boltzmann equation. Meanwhile, the model can be applied to other aquatic animals since the two parameters Cps and ω are considered with physical significance that are related with specie, in which Cps represents its sensitivity to the flow velocity and ω its body size. The model can also be applied to a large scale of the study area by taking advantage of the Eulerian framework used in the model. Chinese sturgeon' distribution was simulated in this paper, with its preference of flow velocity, water depth, substrate and sediment concentration assessed. Compared with the Habitat Suitability Index (HSI) model, the EEHS model produced more accurate results of the distribution of Chinese sturgeon with a correlation coefficient of 0.95, much higher than 0.32 of the HIS model. The simulation results indicate that the habitat condition of Chinese sturgeon downstream of the Gezhou Dam fluctuate when the upstream discharge varies from 4000 to 30,000 m3/s.