Evaluation of tricaine methanesulfonate (MS-222) as a surgical anesthetic for Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus

Dose-response experiments were conducted at 14 and 24 degrees C to evaluate the efficacy and physiological effects of tricaine methanesulfonate (MS-222) to induce and maintain surgical anesthesia in juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). Anesthetic induction time, duration of hyperactivity, recovery time and total handling time of fish were inversely related to MS-222 concentration and water temperature. Minimum effective concentration of MS-222 to maintain anesthesia with fewest signs of stress was 85 mg L-1. Sensitivity to stimuli and body movements progressively increased when fish were exposed to a lower maintenance concentration (70 mg L-1) of MS-222, resulting in reduced biopsy success rates and traumatic injury to internal organs during laparoscopy as fish regained consciousness. Anesthesia with MS-222 resulted in bradychardia, near medullary collapse, elevated signs of stress (plasma cortisol and reddening of the skin) and a generalized hemo-concentration consisting of erythrocyte swelling and increased protein and monovalent ion concentrations. Magnitude of hematologic changes and stress indicators increased with decreasing MS-222 concentration and increased water temperature while plasma chemistry changes increased in magnitude with decreasing MS-222 concentration. This study demonstrates that rapid induction of surgical anesthesia with a relatively high concentration of MS-222 results in reduced signs of physiological stress, and that empirical evaluation of maintenance dosage is important to achieve the best balance between safety, efficacy and stressful side effects for invasive surgical procedures.