Comparative effect of benzocaine, menthol and eugenol as anesthetics for juvenile fat snook

Abstract

The present study evaluated different concentrations of benzocaine, eugenol and menthol for induction of anesthesia in juveniles fat snook (Centropomus parallelus), aiming to determine the most suitable product in terms of induction and recovery time, and the minimum optimal dose for each anesthetic. Concentrations of 50, 75, 100 and 150 mg L^-1 of benzocaine; 25, 37.5, 62.5 and 50 mg L^-1 of eugenol and 50, 100, 150 and 200 mg L^-1 of menthol were tested at 21°C. During the procedure of anesthesia, four stages, from reduction of opercular movements to total loss of reaction to stimulus were monitored. While anesthetized, fish were subjected to biometric procedure and then were placed in an aquarium anesthetic free, to observe the recovery time.  Concentrations of 75, 37.5 and 150 mg L^-1 of benzocaine, eugenol and menthol, respectively, were considered optimal. By presenting several qualities as an anesthetic and also because it can be used efficiently (time to anesthesia in approximately three minutes and recovery in less than five minutes) at low concentrations, eugenol is the most recommended for anesthesia of juvenile fat snook.