The effect of temperature and body weight on the routine metabolic rate and postprandial metabolic response in mulloway, Argyrosomus japonicus

Specific dynamic action (SDA) is the energy expended on the physiological processes associated with meal digestion and is strongly influenced by the characteristics of the meal and the body weight (BW) and temperature of the organism. This study assessed the effects of temperature and body weight on the routine metabolic rate (RMR) and postprandial metabolic response in mulloway, Argyrosomus japonicus. RMR and SDA were established at 3 temperatures (14, 20 and 26 °C). 5 size classes of mulloway ranging from 60 g to 1.14 kg were used to establish RMR with 3 of the 5 size classes (60, 120 and 240 g) used to establish SDA. The effect of body size on the mass-specific RMR (mg O2 kg−1 h−1) varied significantly depending on the temperature; there was a greater relative increase in the mass-specific RMR for smaller mulloway with increasing temperature. No statistical differences were found between the mass exponent (b) values at each temperature when tested against H0: b=0.8. The gross RMR of mulloway (mg O2 fish−1 h−1) can be described as function of temperature (T; 14–26 °C) as: (0.0195T–0.0454)BW(g)0.8 and the mass-specific RMR (mg O2 kg−1 h−1) can be described as: (21.042T–74.867)BW(g)−0.2. Both SDA duration and time to peak SDA were influenced by temperature and body weight; SDA duration occurred within 41–89 h and peak time occurred within 17–38 h of feeding. The effect of body size on peak metabolic rate varied significantly depending on temperature, generally increasing with temperature and decreasing with increasing body size. Peak gross oxygen consumption (MO2: mg O2 fish−1 h−1) scaled allometrically with BW. Temperature, but not body size, significantly affected SDA scope, although the difference was numerically small. There was a trend for MO2 above RMR over the SDA period to increase with temperature; however, this was not statistically significant. The average proportion of energy expended over the SDA period (SDA coefficient) ranged from approximately 7–13% of the total DE intake while the proportion of total energy expended on SDA above RMR ranged from approximately 16–27%