Anesthetic effect of MS-222 at different mass concentrations on Paracobitis variegatus

【Objective】This paper investigated the physiological behavior characteristics of Paracobitis variegatus and the anesthetic effects of various concentrations of 3-aminobenzoic acid ethyl ester methanesulfonate （MS-222）in order to provide anesthesia technical support for the collection of live fish samples in the wild，fish domestication and breeding， and to advance the theory of fish anesthesia.【Method】 Ten groups of MS-222 were set up with the mass concentrations of 35.0， 45.0， 60.0， 70.0， 85.0， 110.0， 140.0， 150.0， 180.0 and 210.0 mg/L to carry out the anaesthesia test of P. variegatus， using static water bioassay. Duration of anesthesia and resuscitation，and the respiratory frequency of P. variegatus under MS-222 immersion baths of different mass concentrations was measured so as to screen mass concentrations of MS-222 anesthetics suitable for domestication，breeding and disease control of P. variegatus.【Result】 Based on different respiratory frequencies and behavioral characteristics after treatment of MS-222 of P. variegatus，the anesthesia degrees could be divided into 6（A₁-A₆）anesthesia stages：irritability，slight sedation，deep sedation，slight anesthesia，anesthesia and deep anesthesia，and resuscitation duration was divided into 4 resuscitation levels，namely resuscitation stage 1-resuscitation stage 4（R₁-R₄）. All the 10 mass concentrations of MS-222 could make P. variegatus reach the A₆（deep anesthesia）， and resuscitate to the R₄ level. According to correlation analysis，significant negative correlations were found between the mass concentration of MS-222 and anesthesia time（R²=0.6003）（P＜0.05，the same below），and the mass concentration of MS-222 significantly positively correlated with resuscitation time（R²=0.7440）；the anesthetic dose significantly affected the anesthesia and resuscitation of P. variegatus. Different mass concentrations of MS-222 had a wavy variation in the respiratory frequency of treated P. variegatus. There were differences in respiratory frequency between anesthesia stage and resuscitation stage with different mass concentrations of MS-222. Under oxygenation，the resuscitation rate of P. variegatus treated with MS-222 at the concentration of 35.0-210.0 mg/L reached 100.0%.【Conclusion】The respiratory frequency of P. variegatus treated with different mass concentrations of MS-222 is discrepant during the anesthesia and the resuscitation stages. The ideal anesthetic concentration of MS-222 for P. variegatus is 45.0-180.0 mg/L. MS-222 at the concentration of 110.0-180.0 mg/L can be used for short-term anesthesia of P. variegatus，while MS-222 at the concentration of 45.0-85.0 mg/L can be used for long-term anesthesia of P. variegatus.