Sustained exercise-trained juvenile black carp (Mylopharyngodon piceus) at a moderate water velocity exhibit improved aerobic swimming performance and increased postprandial metabolic responses

The objectives of this study were to examine whether sustained exercise training at four water velocities, i.e. nearly still water (control), 1 body length (BL) s -1 , 2 BL s -1 and 4 BL s -1 , has effects on swimming performance and digestive metabolism in juvenile black carp ( Mylopharyngodon piceus ). The results demonstrated that fish subjected to sustained training at 2 and 4 BL s -1 showed significantly higher critical swimming speed ( U crit ) and maximum metabolic rate (MMR) over the control group. Fish subjected to sustained training at 1 and 2 BL s -1 showed a significantly (30 and 54%) prolonged duration, 14 and 17% higher postprandial ṀO 2 increment (i.e. ṀO 2peak ), and 62 and 92% more energy expended on specific dynamic action (SDA), respectively, after consuming a similar meal over fish kept in nearly still water. These results suggest that (1) sustained exercise training at a higher speed (2 or 4 BL s -1 ) had a positive influence on the aerobic swimming performance of juvenile M. piceus , which may be associated with improved aerobic metabolism; and (2) sustained exercise training at a lower speed (1 or 2 BL s -1 ) resulted in elevated postprandial metabolic responses in juvenile M. piceus .