Interrelationships between feeding, food deprivation and swimming performance in juvenile grass carp

The present study investigated the interrelationships between feeding, food deprivation and swimming performance in juvenile grass carp Ctenopharynodon idellus. Oxygen consumption, as a function of swimming speed, was determined by fitting data to a power function. Speed exponents from oxygen consumption functions were 1.46, 1.23 and 1.91 with time after feeding of 6 h, 2 d and 2 wk, respectively, which indicated that swimming efficiency increased after digestion was complete and decreased with extended food deprivation. Excess post-exercise oxygen consumption (EPOC) increased slightly with time after feeding, and recovery time varied between 1 and 1.5 h after fatigue. The contribution of anaerobic metabolism began at swimming speeds 28.3 to 40.2% of critical swimming speed (U-crit) and increased with time after feeding. Both optimal swimming speed and critical swimming speed decreased with time after feeding. The metabolic scope of grass carp decreased for at least 6 h after feeding (384 mg O-2 kg(-1) h(-1)). It nearly doubled after 2 d (727 mg O-2 kg(-1) h(-1)) and then declined after 2 wk throughout the duration of food deprivation (420 mg O-2 kg(-1) h(-1)). In conclusion, feeding and food deprivation affected swimming efficiency, metabolism (both aerobic and anaerobic) and swimming capability, with only slight effects on EPOC and recovery time. The results of the present study provide information which will assist in the design of fish ladders and resting pools and thus support fish migration and conservation of biodiversity.