Anaesthetic efficacy and physiological responses to clove oil-anaesthetized kelp grouper Epinephelus bruneus

The efficacy of clove oil as an anaesthetic and at producing a physiological response (plasma cortisol and glucose) was evaluated in the kelp grouper, Epinephelus bruneus. To acquire complete anaesthesia in less than 3 min and recovery in < 10 min, three doses of clove oil were tested at 18, 22 and 26 degrees C. Although higher anaesthetic doses resulted in shorter induction times and longer recovery times, and a lower temperature resulted in longer anaesthesia induction and slower recovery, we found the optimal dose and administering temperature of clove oil to be 250-300 mg L-1 at water temperature of 18 degrees C, 150-200 mg L-1 at water temperature of 22 degrees C and 50-100 mg L-1 at water temperature of 26 degrees C respectively. Following the administration of 150 mg L-1 of clove oil at 22 degrees C, the plasma cortisol level was highest (4.24 +/- 1.571 mu g dL(-1)) after 12 h and the plasma glucose was highest (92.7 +/- 9.61 mg dL(-1)) after 2 h. These results should be useful to the aquaculture industry, where anaesthesia is necessary for a range of activities.