Essential oil of Lippia alba: A new anesthetic for silver catfish, Rhamdia quelen

The aims of this study were to identify the times of anesthetic induction and recovery in silver catfish (Rhamdia quelen) that were exposed to the essential oil of Lippia alba. The efficacy of this oil as an anesthetic and stress-reducing agent and a sensory analysis of fillets prepared from fish exposed to this oil were also performed, juveniles were placed in aquaria containing different concentrations of oil (5, 10, 20, 50, 100, 200, 300, 400, or 500 mg L-1). Plasma cortisol levels were determined in juveniles anesthetized with the lower concentration of the essential oil of L. alba to obtain anesthesia within around 4 min (300 mg L-1) and in control fish, both exposed to the air for 1 min. The essential oil of L. alba could be used at concentrations ranging from 100 to 500 mg L-1 to induce anesthesia (stage 4) in silver catfish. The time required for recovery was shorter when lower concentrations of the oil were used. The essential oil of L. alba inhibited the increase in plasma cortisol levels that was provoked by handling, and the sensory analysis test demonstrated that this oil did not modify the odor or the taste of the fillet. (C) 2010 Elsevier B.V. All rights reserved.