Anaesthetic efficacy of clove oil, Benzocaine, 2-phenoxyethanol and tricaine methanesulfonate in juvenile marbled spinefoot (Siganus rivulatus)

Anaesthetics are used in aquaculture and fisheries to facilitate routine procedures, such as capture, handling, transportation, tagging, grading and measurements that can often cause injury or induce physiological stress. Two experiments were performed to assess the efficacies of four anaesthetic agents, clove oil, benzocaine, 2-phenoxyethanol and MS-222 on juvenile marbled spinefoot rabbitfish (Siganus rivulatus). In the first experiment we tested the lowest effective doses that produced induction and recovery times in 3 min or less and 5 min or less respectively. Dosages were 70 mg L−1 for clove oil, 60–70 mg L−1 for benzocaine, 400 μL L−1 for 2-phenoxyethanol and 100–125 mg L−1 for MS-222. In the second experiment, we determined optimal concentrations of the four anaesthetics if they were to be used to transport rabbitfish fry. Anaesthetic concentrations suitable for handling and transport were: 10–15 mg L−1 of MS-222, 5–10 mg L−1 of benzocaine, 5 mg L−1 of clove oil and 50–100 μL L−1 of 2-phenoxyethanol. All anaesthetic agents are acceptable for use on S. rivulatus, however, 2-phenoxyethanol, MS-222 and clove oil appear to be more suitable than benzocaine. Further studies need to be conducted on effects of high and low doses of anaesthetic agents on physiology of marbled spinefoot.