Determining the tranquilization dose and residue of tricaine methanesulfonate (MS-222) in sea bass Lates calcarifer tissue

Although tricaine methanesulfonate (MS-222) is often used to tranquilize fish, the guidelines for its use in sea bass, a brackish species, have not been established. The aim of the study reported here was to establish the tranquilizing concentration of MS-222, based on the time required for MS-222 residue elimination and withdrawal. Thirty-six fish (6/group) were immersed in different concentrations of MS-222 (0, 30, 50, 60, 70 and 90 mg/l) to evaluate the fish physiological behavior. After 200 fish were anesthetized at 90 mg/l, the fish achieved a healthy recovery within 72 h after the administration of saline. The 10 fish in the control group were subject to the same treatment without anesthesia, 3 out of 10 died. After 108 fish (54/group) were immersed in 30 or 60 mg/l of MS-222, the sedated fish were healthy during and after the 8 h of transport. However, all the 10 fish in the control group died within 3 days. By high-performance liquid chromatography, the residue of MS-222 was assessed. In the skinned muscle and liver, the elimination half-life was 5.54 and 5.27 h (30 mg/l) and 8.72 and 7.15 (60 mg/l), respectively, and the withdrawal time was at least 4.5 days at 30 mg/l and 7.5 days at 60 mg/l.