Effect of MS 222 on respiration and efficacy of forced branchial irrigation with the anesthetic solution in carp

Respiratory parameters were measured with carp in various anesthetic stages, induced with ethyl m-aminobenzoate methanesulfonate (MS 222). Respiration of carp during forced bran-chial irrigation with MS 222 solution was also investigated. Sedation was induced in 20 ?? 70mg. l-1 solutions of MS 222. Deep anesthesia was induced in the solutions over 85mg. l-1. Respiratory movement stopped in the solutions over 90mg. l-1. Under this concentration, carp uptook enough oxygen from water owing to gill ventilation kept at normal level. Judging from changes of the respiratory parameters, carp is considered to be anesthetized deeply and safely with MS 222 solution of 85-90mg. l-1, when the initial pH of the water before adding MS 222 is 8.0-8.4. In solutions of 100-150mg. l-1 in concentration of MS 222, high enough to stop the respiratory movement of carp, the forced branchial irrigation with the anesthetic solution assisted fish to uptake necessary oxygen from the ambient water.