Effect of exercise training on the swimming behaviour and rheotaxis of Procypris rabaudi

Procypris rabaudi is a key stocking species in the upper Yangtze River. To determine the appropriate intensity and duration of exercise training for enhancing their field survival rate, we examined the changes in swimming capacity and rheotaxis between the trained group (exercised at 60% critical swimming speed for 6 hours daily) and the control group (reared in static water) under different training intensities and durations. Results would help explore optimal pre-release exercise protocols for hatchery-reared fish. The results showed that after five weeks of training at 60% of the critical swimming speed, the critical swimming ability of P. rabaudi increased from the initial 0.59 m·s^-1 to 0.62 m·s^-1. After the four weeks, the number of reversals of the young rock carp in the training group began to decrease. After six weeks, the decline in the number of reversals was the most obvious. After five weeks of exercise training, there was a significant difference in the tail swing amplitude between the young rock carp in the training group and the control group, and the tail swing amplitude of the control group was significantly higher than that of the training group. The exercise training enhanced the ability of the young rock carp to resist the current and swim upward. Considering the positive effects of various exercise training durations on the swimming ability and tropism of P. rabaudi, it was proposed that at least five weeks of exercise training at 60% of the critical swimming speed for six hours per day would be an ideal preparation program for P. rabaudi prior to the release.