A Classification Method for Fish Swimming Behaviors under Incremental Water Velocity for Fishway Hydraulic Design

Critical swimming speed at different temperatures for small-bodied freshwater native riverine fish species

This study evaluated the effect of fish total length (LT) and three water temperatures (10, 15 and 20 °C) on the critical swimming speed (Ucrit) of the species Percilia irwini (2.9-6.3 cm LT), Cheirodon galusdae (3.4-5.5 cm LT), and Trichomycterus areolatus (4.0-6.3 cm LT). An Ucrit estimation model was constructed for each species as a function of temperature and size. The results showed mean Ucrit for P. irwini of 44.56, 53.83 and 63.2 cm s-1 at 10, 15 and 20 °C, respectively: 55.34, 61.74 and 70.05 cm s-1 for C. galusdae and 56.18, 63.01 and 71.09 cm s-1 for T. areolatus. Critical velocity depended on the interaction between species, body length and water. The swimming performance increased significantly with rising temperature in all three species. The velocity also increased with greater fish total length. After controlling for fish total length, velocity also increased with higher temperature in the three species. This research is relevant to small fish species that require conservation measures.

Swimming ability of Schizothoracinae fishes in Yarlung Zangbo River of China

The Yarlung Zangbo River is a river with abundant hydropower resources but fragile biodiversity in China. As an important benchmark for both research and ecological management, there is still a lack of knowledge about the swimming ability of fishes in the Yarlung Zangbo River. The induced flow velocity (Uind), critical swimming speed (Ucrit), and burst swimming speed (Uburst) of five Schizothoracinae species were tested in this study. Relative swimming ability related to body length and body shape was calculated. The results indicated that the average absolute swimming speeds (Uind-a, Ucrit-a, and Uburst-a) of all the experimental fish were 10.20 ± 0.01, 57.58 ± 3.28, and 69.54 ± 2.94 cm/s, respectively, and the corresponding relative Uind, Ucrit, and Uburst related to body length (Uind-l, Ucrit-l, Uburst-l) were 1.15 ± 0.07, 5.04 ± 0.26, and 7.23 ± 0.28 BL/s, respectively. Moreover, relative Uind, Ucrit, and Uburst related to body shape (Uind-s, Ucrit-s, and Uburst-s) were 0.80 ± 0.13, 2.49 ± 0.51, and 4.32 ± 0.57 cm-2/s, respectively. No significantly differences in relative swimming speeds existed among five species. Only Oxygymnocypris stewartii was significantly weaker in Uburst-s than Schizothorax o'connori. The body shape showed a stronger relationship with swimming speed than the body length did. Schizothoracinae fish in the Yarlung Zangbo River basin are less sensitive to the water flow and performed weaker Ucrit and Uburst compared to those in the Yangtze River basin, indicating that Schizothoracinae fish in the Yarlung Zangbo River may be more susceptible to threats from environmental changes. The paper enriched the research on the swimming ability of Schizothoracinae fishes and provided efficient data for the fish conservation in the Yarlung Zangbo River.

Swimming performance of Cyprinus carpio (Carp) in China

Cyprinus carpio (Carp) is a fish of great economic importance in China. However, its population has declined considerably due to the construction of barrages. Thus, fishways need to be constructed at barrages to protect fish resources. It is essential for the fishway design to study the swimming performance of carp. By applying incremental flow velocities in a glass open-type flume, three indicators of swimming performance of the carp in China with the body length (BL) of 13-21 cm, including the induced flow velocity (IFV), the critical swimming speed (U_crit) and the burst swimming speed (U_burst), are systematically assessed. The correlation between the swimming performance and the BL is also analyzed. The results indicate that the IFV of the carp is 15.56 ± 1.79 cm/s, which is not significantly influenced by the BL. The value of U_crit varies from 60 to 82 cm/s and gradually increases with the increasing value of BL. The relative critical swimming speed (U'_crit) is 4.23 ± 0.28 BL/s and gradually decreases with the increasing value of BL. The value of U_burst ranges from 77.2 to 105.1 cm/s, which is linearly positively correlated to BL. The relative burst swimming speed (U'_burst) is 5.42 ± 0.39 BL/s. The value of U_burst is approximately 1.28 times of that of U_crit for the carps with the same BL. These findings are meaningful to the further study of ecological behavior and to the fishway design and optimization of carps.

Relationship between Upstream Swimming Behaviors of Juvenile Grass Carp and Characteristic Hydraulic Conditions of a Vertical Slot Fishway

The successful fish upstream movement through a dam/gate is closely associated with the hydraulic conditions of a fishway. To improve the passage efficiency, this study investigated the upstream swimming behaviors of juvenile grass carp, a representative fish of four major Chinese carps, under characteristic hydraulic conditions of a designed vertical slot fishway model. The impacts of different discharges and baffle lead angles on the successful movement of test fish were analyzed, and the selection of the movement trajectory was studied through overlay of their upstream swimming trajectories on the water flow field resulting from numerical modeling. We found that under the same discharge, the percentage of successful test fish movement with a lead angle of 45° was higher than 60° and 30°. Within a fixed lead angle, the higher the discharge, the lower the percentage of successful movement. During upstream movement, the test fish had a preferred water velocity of 0.01–0.45 m/s in the pool, and avoided areas where the turbulence kinetic energy (TKE) was greater than 0.012 m2/s2. These results provide a basis for the hydraulic design of vertical slot fishways and a reference for studying swimming behaviors of other fish species.

Schizothorax prenanti swimming behavior in response to different flow patterns in vertical slot fishways with different slot positions

Fish swimming behavior is a critical parameter for the design of vertical slot fishways. Although Schizothorax prenanti is a significant reproductive potamodromous migratory fish species in the upper reaches of the rivers in Southwest China, its swimming behavior has not been extensively researched. Therefore, in this study, a comparative experiment was conducted in vertical slot fishways to analyze the behavior of Schizothorax prenanti in response to different flow patterns, with respect to different slot positions. The experimental model was designed with a length scale of 1:4, and a method for selecting the appropriate fish size in the scaled physical model was proposed. Based on these experiments, it was found that the typical upstream trajectories of Schizothorax prenanti are traceable to the sidewall of the pool, which are characterized by low velocity and turbulent kinetic energy (TKE). The hydraulic variables exhibited an asymmetric distribution within the vertical slot, and the fish were found to pass through the area with the lowest velocity and TKE. A flow pattern with a guide wall length-to-pool width ratio of P/B = 0.25, in which Schizothorax prenanti can immediately find the sidewall, is suitable for fish migration. Therefore, this is the recommended value for the construction of effective vertical-slot fishway structures.