The efficacy of the oils of spearmint and methyl salicylate as new anesthetics and their effect on glucose levels in common carp (Cyprinus carpio L., 1758) juveniles

In aquaculture and fisheries research, anesthetics are generally necessary to ease handling and to minimize stress and physical injury of fish during various handling procedures. The purpose of this study was to evaluate the effects of two anesthetics of spearmint oil (SO) and methyl salicylate oil (MSO) on Cyprinus carpio (16.59±0.43g). Also, their effect on glucose values was investigated as well. Fish were exposed to different concentrations of the SO (3, 5 and 7mlL−1) and the MSO (1, 2 and 3mlL−1) for induction of anesthesia. Results showed that induction time decreased significantly with increasing of the concentration of the SO or the MSO (P<0.05). However, recovery time increased significantly with increasing of the concentration of anesthetics (P<0.05). Opercular rate first increased and then slowly decreased with increasing the concentration of anesthetics. Glucose levels were significantly affected by concentration of anesthetics (P<0.05). For the SO and the MSO, the lower levels of glucose after anesthesia and recovery belong to concentrations of 5 and 2mlL−1, respectively. In another experiment, common carp exposed to the SO (5mlL−1), the MSO (2mlL−1) and spearmint oil and methyl salicylate oil emulsion (CMSE), as a combination anesthetic, in order to their compare with each other. Anesthesia induction was more quickly in the CMSE group; Also, recovery was significantly quicker in the CMSE group compared to other treatments (P<0.05). There were no significant differences in glucose levels after induction of anesthesia between groups (P>0.05). However, the glucose levels after recovery increased significantly in the MSO group (P<0.05). No mortality was observed in the study. These findings suggested that SO, MSO and CMSE anesthetics are useful anesthetics for common carp juveniles. In addition, combination anesthesia allowed a reduction of the dosages used for inducing anesthesia and produced markedly reduced recovery times compared to agents administered individually.