Evaluation of 2-phenoxyethanol and menthol as anaesthetic agent in tilapia

Abstract

This study aimed to determine the induction and recovery time in Nile tilapia (Oreochromis niloticus) submitted to the anaesthetic agents 2-phenoxyethanol and menthol. Five concentrations were evaluated of the 2 phenoxyethanol (0.45 mL L^-1; 0.60 mL L^-1; 0.75 mL L^-1; 0.90 mL L^-1; 1.05 mL L^-1) and menthol (50 mg L^-1; 75 mg L^-1; 100 mg L^-1; 125 mg L^-1; 150 mg L^-1) in masculinized juvenile tilapia. The experiments were conducted independently in a completely randomized design (CRD), consisting of five treatments for each anaesthetic and 20 repetitions (fish) per treatment. The induction and recovery from anesthesia were divided into three stages, according to the fishes' behavior under the effect of the anesthetic, recording the length of time for each stage. Limnological parameters of water were controlled (pH and dissolved oxygen). Statistical analysis was performed using a generalized linear model with gamma distribution. From this study, it is possible to conclude that, for Nile tilapia juvenile under the same conditions of maintenance, with increasing concentration of 2-phenoxyethanol and menthol there is a reduction in the time of anesthetic induction and recovery. Concentrations of 0.90 mL L^-1 of 2-phenoxyethanol and 125 mg L^-1 of menthol were suitable for anesthetic induction in tilapia.