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.