The effects of swimming exercise on growth and whole-body protein and fat contents of fed and unfed fingerling yellowtail

SUMMARY: Fingerling yellowtail Seriola quinqueradiata (initial mean body weight 4.3 g), an active pelagic fish, were reared under fed (4 weeks) and unfed (1 week) conditions to investigate the effects of swimming exercise on growth performance and whole body composition. The fish were raised in three water velocities: < 0.3 body length/s (bl/s), 1.0 bl/s, and 2.25 bl/s and fed diets containing two fat levels (13.2 and 20.3%). The exercised fish had significantly higher weight gains and feed efficiencies than the unexercised fish in both dietary fat levels. A second-order polynomial suggested that the optimum water velocity for the growth occurred at about 1.6 bl/s. The whole-body crude protein and fat contents were higher in the exercised fish than in the unexercised fish, and consequently apparent body protein and fat retentions were improved in both dietary fat levels by swimming. However, during 1 week starvation, body fat loss/g body weight loss was higher in the exercised fish than in the unexercised fish. The results of the present study clearly show that swimming condition improves growth performance of fingerling yellowtail, and suggest that swimming exercise stimulates both anabolism and catabolism of protein and fat; however, under fed conditions anabolism appears superior to catabolism.