Effect of Temperature Gradient on the Critical Swimming Speed of Four Major Chinese Carps

Abstract:

Fishways are important ecological compensation measures that come with the construction of waterpower dams. Investigation of their swimming capability will provide the basis required for the design of fishery passage facilities. In this study, we used four major Chinese carp species to measure critical swimming speeds under five temperature gradients (10℃, 15℃, 20℃, 25℃, and 30℃). The results showed that the relative critical swimming speeds of Mylopharyngodon piceus, Ctenopharyngodon idellus, Hypophthalmichthys molitrix, and Aristichthys nobilis were (3.93±0.24)~(9.94±1.65) BL/s, (3.50±0.48)~(10.55±2.07) BL/s, (0.95±0.04)~(4.68±0.58) BL/s, and (2.22±0.18)~(3.95±0.23) BL/s, respectively, across 10℃~30℃. The absolute critical swimming speed and relative critical swimming speed of the four major Chinese carp species increased with the increase in water temperature at 10℃ to 20℃. The absolute critical swimming speed and relative critical swimming speed reached a maximum at 20℃, and then tended to stabilize. The swimming capability at 20℃ was significantly higher than that at 15℃ and 10℃, but was not significantly different from that at 25℃ and 30℃. In addition, the critical swimming speeds of C. idellus increased faster than that of the other three species of the four major Chinese carp, as the temperature increased. At the same temperature, the critical swimming speeds of C. idellus and M. piceus were similar, and significantly higher than those of H. molitrix and A. nobilis (P<0.01). Based on the results of this study, we suggest that the opening time of the fishway should be extended in the summer in the year, and the critical swimming speed of A. nobilis should be taken as the main basis during fishway designing.