Physiological responses of hybrid striped bass under sedation by several anesthetics

Abstract

Several aquatic anesthetics, in doses low enough not to change the swimming behavior, alone and in combination with NaCl, were evaluated for their effectiveness to suppress the stress response in sunshine bass ( Morone chrysops× Morone saxatilis). Clove oil, Aqui-S®, metomidate, MS-222, quinaldine, and quinaldine sulfate were used alone or combined with 5 g/l NaCl. The stress response was evaluated by measuring plasma cortisol, glucose and chloride concentrations in fish after exposure to each of the compounds and after exposure in fish subjected to stress while exposed to each of the compounds. Stress was induced by lowering the water in the aquarium for 15 min. Exposure to all of the compounds, except metomidate, resulted in a significant increase in plasma cortisol and glucose. The cortisol increase induced by exposure to NaCl alone was transient, but NaCl did not reduce the response due to stress. The same pattern of response occurred when the anesthetics were given with NaCl. Only exposure to quinaldine resulted in an increased glucose concentration and plasma glucose was higher than controls in stressed fish exposed to clove oil and quinaldine sulfate. Metomidate may have promise in suppressing the stress response in hybrid striped bass; however, the only approved anesthetic for use in food fish is MS-222. Exposure of fish to MS-222 induced the stress response and did not suppress the magnitude of the stress response in fish exposed to low-water stress. These data point out the importance of continuing to develop and approve compounds for use in aquaculture.