Minne Li’s research while affiliated with China Three Gorges University and other places

Total dissolved gas supersaturation (TDGS) due to flood or hydropower station discharge adversely affects the swimming performance of migratory fish, thereby reducing passage efficiency. This study assessed the swimming performance of bighead carp in an experimental vertical slot fishway under varied slot flow velocities of 0.2, 0.25, and 0.3 m/s after 2 h of exposure to different levels of TDGS water. The results demonstrated that increased TDGS levels and flow velocities significantly reduced the fish passage efficiency. Specifically, passage success rates reached 61%, 48%, 37%, and 37% at TDGS levels of 100%, 110%, 120%, and 130% respectively, at a flow velocity of 0.2 m/s. At flow velocities of 0.2, 0.25, and 0.3 m/s with 100% TDGS water, success rates were 61%, 53%, and 47%, respectively. Moreover, increased TDGS levels and increased flow velocities notably extended the passage time in the fishway. Both TDGS levels and fishway flow velocities significantly influenced the swimming trajectories of the fish. Preferences for flow velocities were notably affected by the TDGS levels, whereas preferences for turbulent kinetic energy were affected by both the TDGS levels and the velocities of the fishway flow. In this study, an evaluation method was developed to assess the adverse effects of TDGS on fish passage efficiency based on the following critical parameters: passage success rate, time, trajectory, and preferred hydraulic factor. This study offers valuable insights for optimizing operations and fishway management to enhance fish protection.

The hydrodynamics at the fishway entrance play an important role in attracting fish into a fishway. Adjusting the entrance angle of the fishway to allow suitable water flow patterns at the entrance is an effective measure that can be used to improve the attraction efficiency. In this study, we analyzed the movement behavior of grass carp (Ctenopharyngodon idella) in a river channel at a fishway entrance with different fishway entrance angles (30°, 45°, and 60°) and different replenishment velocities (0.1 m/s, 0.2 m/s, and 0.3 m/s). The flow velocity was 0.32–0.50 m/s when the fish head deflected into the entrance under different entrance angles for grass carp. As the entrance angle of the fishway increased, the fish energy consumption increased. The range of energy consumption for grass carp increased from 1.26–3.59 × 10⁻³ J to 3.32–7.33 × 10⁻³ J when the entrance angle was increased from 30° to 60°. There was a negative correlation between the entrance angle of the fishway and the deflection angle of the tested fish’s head. This research presents a reference that combines fish swimming behavior and hydraulics to optimize the design of fishway entrances.

During the flood season, high dam operations for flood discharge result in total dissolved gas (TDG) supersaturation. This condition causes gas bubble trauma (GBT) and can even lead to fish mortality, posing a significant threat to downstream river ecosystems. Assessing the ecological risks of TDG presents a major challenge in water power-intensive river basins worldwide. Limited research has explored the impact of TDG on fish behaviors such as aggression and memory, which are crucial for feeding, reproduction, and predator avoidance. This study investigated the effects of acute TDG supersaturation stress on swimming behavior, aggression, and memory in medaka. Results indicated that Medaka exposed to 115% and 130% TDG supersaturation for 2 hours showed significantly reduced swimming performance. At TDG levels of 100%, 115%, and 130%, medaka displayed activity rates in the mirror arm of 44.34 ± 12.88%, 40.27 ± 15.44%, and 35.35 ± 16.07%, respectively, and in the active stimulus arm of 50.35 ± 14.75%, 40.76 ± 12.51%, and 35.35 ± 18.47%, respectively. As TDG levels increased, both aggression and memory in medaka significantly declined. The findings of this study could contribute to developing a TDG ecological risk assessment model based on fish memory and aggression, providing essential data for ecological management strategies to mitigate the adverse effects of TDG.

Simple Summary Exploring the behavioral strategies of fish in response to complex hydrodynamic environments is an important scientific focus in fish habitat enrichment research. The results of this research indicated that (1) the swimming speed of fish schooling (three fish) was significantly lower than that of individual fish, (2) fish schools performed obvious slow-speed exploration behavior during upstream migration, and (3) fish mainly tended to occupy low and medium flow velocity areas. The results of this research enrich the knowledge of fish behavioral responses to spatially heterogeneous turbulent flows, which is an important aspect for developing reliable and accurate estimates of fish passage facilities and husbandry environments. Abstract Spatially heterogeneous turbulent flow refers to nonuniform flow with coexisting multiple flow velocities, which is widely distributed in fish natural or husbandry environments, and its hydraulic parameters affect fish swimming behavior. In this study, a complex hydrodynamic environment with three flow velocity regions (low, medium, and high) coexisting in an open-channel flume was designed to explore volitional swimming ability, the spatial-temporal distribution of fish swimming trajectories, and the range of preferred hydrodynamic parameters of Schizothorax prenanti individual and schooling (three fish). The results showed that the swimming speed of individual fish during upstream migration was significantly higher than that of fish schools (p < 0.05). The swimming trajectories of fish schooling showed that they spent more time synchronously exploring the flow environment during upstream migration compared with individual fish. By superimposing the fish swimming trajectories on the environmental flow field, the range of hydrodynamic environments preferred by fish in complex flow fields was quantified. This research provides a novel approach for investigating the natural swimming behavior of fish species, and a theoretical reference for the restoration of fish natural habitats or flow enrichment of husbandry environments.

The migration corridors in regulated rivers lead downstream fish migrants, particularly juveniles to pass through water infrastructure. Accelerating flow, experienced by fish, might trigger avoidance behaviour and then influence the downstream migration efficacy. It is essential to understand the causes of avoidance behaviour exhibited by downstream migratory fish in accelerating flow. In this study, the effect of three different accelerating flows on the downstream migration behaviour of Schizopygopsis younghusbandi (S.Y) was investigated using a constriction wedge in a circulating flume. The results showed that some fish (30%, 23%, and 39% under low, medium, and high flow conditions, respectively) repeatedly attempted to burst upstream with positive rheotaxis prior to successful passage downstream. Under the low-, medium-, and high-accelerating levels, the average fish swimming speeds were 89.19, 91.28, and 111.94 cm/s, respectively; these values were close to the critical swimming speed (110.42 cm/s) of the target fish. The water velocities at the fish avoidance points were centrally distributed at approximately 73.03 cm/s. Regarding turbulence, the results exhibited that the S.Y generally responded to a discrete range of <50 cm 2 /s 2 of turbulent kinetic energy and < 2 N/m 2 of the horizontal component of the Reynolds shear stress (RSS xy). Also, the fish that exhibited avoidance behaviour were not centrally distributed in the lateral and longitudinal velocity locations, where there was an abrupt change in the gradient. This study highlighted the impact of accelerating flow on the downstream fish migration behaviour of a cyprinid. Furthermore, this study quantified the hydraulic factors that triggered this avoidance. Thus, it provided experimental support for optimizing the design of the hydraulic factors for downstream fishways.