Swimming Performance in Large Yellow Croaker: Effects of Group Size, Test Protocol, and Recovery Time On Critical Swimming Speed

Swimming is critical for fish survival, and little attention has been paid to the swimming performance of large yellow croaker, the largest farmed marine fish in China. To address this gap, we conducted a study to measure the critical swimming speed (U_crit) of 1050 croaker in a designed swim test flume. Our findings shed light on the effects of group size, U_crit test protocol, and recovery time on swimming performance. The water flow in the swim flume increased steadily and linearly. The linear fit equation was y = 2.89x + 1.79 with an R² of 0.99. With the help of the swim flume, we found that group size, and the U_crit test protocol had a significant effect on the U_crit values, except for the recovery time: The U_crit values obtained in the ramp-U_crit test averaged 28.32 ± 6.11 cm.s⁻¹, which was significantly lower than that obtained in the traditional U_crit test of 32.75 ± 7.60 cm.s⁻¹; The U_crit value of a group size of 50 fish was 33.51 ± 5.96 cm.s⁻¹, which was significantly higher than that of a group of 200 fish (28.49 ± 6.37 cm.s⁻¹). These results provide insights into the swimming performance of large yellow croaker and can be used to standardize the swimming test protocols.