Effects of Aerobic Exercise Training on the Growth, Swimming Performance, Antipredation Ability and Immune Parameters of Juvenile Rock Carp (Procypris rabaudi)

Simple Summary The artificial release of hatchery fish has not achieved expected results, mainly due to the low survival rate of the fish after being released into the natural environment. Many studies have shown that the implementation of pro-released training can improve the survival rate of hatchery fish. Rock carp (Procypris rabaudi) is a rare breed of fish in the upper and middle reaches of the Yangtze River. The aim of this study is to investigate whether aerobic exercise training has positive effects on the growth, swimming ability, antipredation ability and immunologic function before releasing the species into the wild. The findings from this study indicate that the training regime at close to 2-4 bl s(-1) for 20 h per day for 42 days prior to release might be a suitable strategy to promote the survival rate of released juvenile rock carp in the wild. Many studies have found that aerobic exercise training at a moderate water velocity can improve the growth, swimming performance and survival rate of fish. To investigate the effects of aerobic exercise training on the growth, swimming performance, antipredation ability and immune parameters of rock carp, juveniles were placed in training channels with different water velocities (i.e., 3 cm s(-1), 1 (body length s(-1)) bl s(-1), 2 bl s(-1) and 4 bl s(-1)) for 6 weeks. Then, the specific growth rate, critical swimming speed (U-crit) and its metabolism, constant acceleration speed (U-cat), survival rate under predation, spleen index, lysozyme (LZM) activity and immunoglobulin (IgM) level were measured. Training showed no significant effect on the length-specific growth rate, weight-specific growth rate, U-crit, maximum metabolic rate (MMR), metabolic scope (MS), U-cat or spleen index. The resting metabolic rates (RMRs) of the 2 bl s(-1) and 4 bl s(-1) training groups were significantly higher than those of the control group and 1 bl s(-1) training group. The survival rate of the 1 bl s(-1) training group in the presence of predators was significantly higher than that of the control group but significantly lower than those of the 2 bl s(-1) and 4 bl s(-1) training groups. The LZM activity of the 4 bl s(-1) training group was significantly higher than that of the control group. The IgM level of the 2 bl s(-1) training group was significantly higher than that of the control group. These data indicate that aerobic exercise training does not improve the growth and swimming performance of juvenile rock carp but can improve their antipredation ability and immunologic function.