| The Chinese catfish(Silurus asotus Linnaeus)is a widely distributed carnivorous and economic fish species. It was used as an experimental model in our study at 25±1℃. Thirty-four juvenile Chinese catfish(19.36-46.95g)were divided into five groups, each group was starved for 0, 1, 2, 4 and 8 weeks, respectively. The aim of this study was to investigate the effect of the fasting on the resting metabolic rate(RMR), body composition and the excess post-exercise oxygen consumption and reveal the life strategy for starvation in the juvenile Chinese catfish. The results showed that the juvenile Chinese catfish of 8 week fasting groups losed the mean body mass (fresh weight) from 38.99±2.91 to 30.41±2.03g dramatically by 22.01%. The oxygen consumption rate and resting metabolic rate both gradually decreased in starvation, the former decreased from 5.77±0.35 to 1.65±0.17mgO2h-1, reduced by 71.4%, and the latter decreased from 63.19±3.68 to 22.38±1.36mgO2kg-1h-1, reduced by 64.58%.The resting metabolic rate of which starved for eight weeks was analysed in the juvenile Chinese catfish, and we found there were three steady periods: their RMR were 41.62±0.34, 34.72±0.55 and 27.59±0.52 mgO2kg-1h-1(P<0.05), and their duration were 10, 14 and 27d, respectively.The crude lipid, energy content, moisture and ash all changed dramatically when the Chinese catfish were starved for four weeks, the formers two decreased by 64.8% and 15.27%, but the latter two increased by 1.95% and 11.36%, respectively. While the crude protein did not descend significantly until the 8 week fasting group, decreased by 23.56%.Before the exhaustive exercise, the resting oxygen consumption rate(ROCR)of each fasting group in the juvenile Chinese catfish were 2.21±0.15, 1.63±0.04, 1.64±0.13, 1.44±0.08 and 0.98±0.09mgO2kg-1min-1, respectively. ROCR of the 1, 2 and 4 week fasting group were not different significantly, so they three showed a steady period in starvation which duration was from the 1 to 4 week. The mean ROCR of the steady period was 71.04% at the 0 week fasting group. After the exhaustive exercise, the oxygen consumption rate of the five fasting groups reached their peak soon in two minutes, then decreased quickly. The peak oxygen consumption rate of each group was 7.35±0.72, 7.95±0.45, 9.05±0.51, 7.53±0.18 and 6.24±0.22 mgO2kg-1min-1, respectively. The oxygen consumption rate finally reached the steady VO2 post-exercise which was a little higher than the resting metabolic rate. Peak oxygen consumption rate of the five groups was 3.38, 4.92, 5.63, 5.32 and 6.68 times than their resting metabolic rate, respectively.The EPOC of each group was 31.8±6.06, 76.67±4.34, 69.2±5.89, 70.41±3.12 and 38.28±2.72 mgO2kg-1min-1, respectively. The EPOC of the 1, 2 and 4 week fasting group were not different significantly, and their mean value was 126.71% higher than the 0 week fasting group(P<0.05). EPOC of the 8 week fasting group decreased dramatically, and was not different from the 0 week fasting group significantly. EPOC of the five groups showed a change which increased first then decreased.The results demonstrated that the juvenile Chinese catfish lowered its RMR during fasting. The longer the duration, the lower the RMR, then the longer the steady period. In starvation, the juvenile Chinese catfish consumed lipid much more than the protein at first, and usually started to use the protein mostly after the lipid was consumed a lot. The juvenile Chinese catfish was similar to most fish species.A certain term fasting evoked a compensatory effect of the EPOC in the juvenile Chinese catfish, and the time of the compensatory effect was about 3 weeks.Duration of the steady period in ROCR was absolutely accordant with the compensatory time of the EPOC. This phenomenon demonstrated that they two have an underlying relationship.
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