etabolic response was investigated in southern catfish Silurus meridionalis at 27.5℃. The results showed that there was no significant difference in the specific dynamic action (SDA) coefficient among the groups of different feeding levels (P >0.05). The duration increased from 26.0 to 40.0 h and the peak metabolic rate increased from 207.8 to 378.8 mg O2 kg-1 h-1 when the feeding level was increased from 0.5 to 4%. The relationship between the peak metabolic rate (RP, mg O2 kg-1 h-1) and FL could be described as: RP =175.4 t 47.3 FL (r2 = 0.943, n = 40, P < 0.001). The relationship between the SDA duration (D, h) and FL could be described as D=30.97FL0.248 (r2=0.729, n=40, P < 0.001).

Resting metabolic rate in southern catfish of 2 and 5 day fasting groups were significantly higher than that of the 15 day fasting group (P < 0.05). After feeding, peak metabolic rate of specific dynamic action (SDA) of the 15 day fasting group was significantly lower than that of the 2 and 5 day fasting groups (P < 0.05). The duration of the SDA of the 15 day fasting group was significantly longer than that of the 2 day fasting group (P < 0.05) and the SDA coefficient of the 15 day fasting group was significantly lower than that of the 2 day fasting group (P < 0.05).

The effect of relative meal size (0.5–24% body mass) on specific dynamic action (SDA) was assessed in Chinese catfish (Silurus asotus Linnaeus) (30.90±1.30 g) at 25.0℃; the cutlets of freshly killed loach without viscera, head and tail were used as a test meal. There was no significant difference in either SDA duration or peak oxygen consumption (VO2) among low meal size ranges. But both increased linearly as meal size increased from 2 to 24% without reaching a plateau. Factorial metabolic scope was 5.92 in fish fed with 24% body mass, the highest documented feeding metabolic scope value in fish till now. The Peak VO2 of satiated meal size groups (175.85±10.55 mg O2 h-1) was above 80% of maximum metabolic rate during locomotion recovery process (215.48±7.07 mg O2 h-1). The relationship between energy expended on SDA (E) and energy ingested (I) was described as: E=0.0000432I2+0.140I+2.12. The lowest value of SDA coefficient appeared at 2% body mass group.