Abstract: Analyzing the swimming behavior of fish during upstream migration and its response to the hydraulic conditions of fishway is the key to optimizing fishway design and improving the upstream efficiency and success rate of fish. Taking Schizothorax o’connori as the research object, we analyzed the influence of each hydraulic factor on the reentry behavior and renewed upstream migration by combining the flow field, turbulent kinetic energy field and strain rate field with the upstream migration or reentry trajectories of fish together. We further explored the underlying causes of reentry behavior by combining the energy consumption rate of fish during upstream migration. The results showed that fish had general reentry behavior during upstream migration, and most of its reentry behavior was to search for a suitable path of upstream migration. The velocity of fishway was the dominant factor triggering the reentry behavior. The reentry behavior of fish was concentrated in the high velocity regions. After reentry, the fish tended to select low velocity regions to renew upstream migration. The turbulent kinetic energy had a significant contribution to the direction of reentry movement. Fish tended to return from lower turbulent kinetic energy regions, and selected higher turbulent kinetic energy regions to renew upstream migration. The strain rate had a relatively minor effect on the reentry behavior. Results of correlation analysis between the hydraulic factors and the energy consumption rate at the track points of upstream migration indicated that the high energy consumption and physiological stress were the internal causes that triggered the reentry behavior.

Key words: Morus alba, climate change, growth., leaf quality