Anesthetic effects of MS-222 and eugenol in simulated transportation of juvenile largemouth bass (Micropterus salmoides)

To determine the appropriate anesthetic method and dose for juvenile Micropterus salmoides in laboratory, we compared the hydrostatic anesthesia effects of two common fish anesthetics (MS-222 and eugenol) on the juveniles with different concentrations (40 mg·L^–1, 50 mg·L^–1, 60 mg·L^–1, 70 mg·L^–1, 80 mg·L^–1, 90 mg·L^–1, 100 mg·L^–1 and 8 mg·L^–1, 10 mg·L^–1, 12 mg·L^–1, 14 mg·L^–1, 16 mg·L^–1, 18 mg·L^–1, 20 mg·L^–1). The results show: 1. With increasing concentrations of the two anesthetics, the anesthetic time shortened but the recovery time prolonged. 2. The optimal anesthetic concentrations of MS-222 and eugenol were 70 mg·L^–1 and 16 mg·L^–1, respectively, while the optimal anesthetic transportation concentrations of the two anesthetics were 50 mg·L^–1 and 10 mg·L^–1, respectively. Then we carried out an experiment of 10-hour anesthesia transport under the optimal anesthetic concentrations of MS-222 and eugenol , and the survival rate during the transportation and after 24 h of recovery for the anesthesia group were both 100%, significantly higher than those for the non-anesthetic transport group (P<0.05). The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels increased significantly in the anesthesia transport group compared with those in the non-anesthetic transport group and hydrostatic control group (P<0.05). The ALT and AST levels in the MS-222 anesthesia group were significantly higher than those in the eugenol anesthesia group (P<0.05).