THE COMPARATIVE AEROBIC METABOLISM OF BARRAMUNDI Lates calcarifer AND BROWN-MARBLED GROUPER Epinephelus fuscoguttatus.
Barramundi, Lates calcarifer, and brown-marbled grouper, Epinephelus fuscoguttatus, are both important tropical aquaculture species. They are euryhaline and eurythermal with a high degree of plasticity to increasing temperature. Little has been documented on the aerobic metabolism of these species. Here, we determine the routine metabolic rate (RMR), maximum metabolic rate (MMR) and aerobic scope (AS). Aerobic metabolism of barramundi with a mean body weight of 262.5±3.85 g and brown-marbled grouper with a mean body weight of 294.5±2.61 g was measured across a 20 °C temperature range (18, 28 and 38 °C) and expressed as a function of temperature (T) per mg O2 kg-0.8 h-1 as: Barramundi RMR = 3.464T - 27.605, MMR = 7.67T + 0.2067 and AS = 4.212T + 27.684. The energy equivalent was calculated for RMR as 11.49, 22.32 and 34.08 kJ kg -0.8 day -1 for routine energetic demand and for MMR as 43.47, 73.35 and 93.51 kJ kg -0.8 day -1 for maximum energetic demand at 18, 28 and 38 °C, respectively. Brown-marbled grouper RMR = 0.0827T2 - 0.8139T + 8.5516, MMR = -0.686T2 + 44.686T - 461.38 and AS = -0.768T2 + 45.468T - 469.59. The energy equivalent was calculated for RMR as 6.75, 16.49 and 31.63 kJ kg -0.8 day -1 for routine energetic demand and for MMR as 39.37, 82.19 and 80.27 kJ kg -0.8 day -1 for maximum energetic demand at 18, 28 and 38 °C.
The aerobic metabolism of juvenile barramundi continues to increase linearly with temperature to the upper extreme of the ecologically relevant temperature range (38 ◦C). In contrast the response of brown-marbled grouper followed a bell-shaped curve with the vertex at 29.6 °C implying a thermal optima for this species.. This provides practical information for suitable thermal range for aerobic scope i.e. at 28 °C AS for barramundi is 22.3% less than brown-marbled grouper, as well as describing the thermo senitivities of barramundi and brown-marbled grouper across an ecological relevant temperature range.