2-Phenoxyethanol as an anesthetic for Rhamdia quelen: a comparison with eugenol.

Aquaculture handling requires fast anesthesia, assuming that action-time is within 3 min and recovery in <5 min.This study aimed to verify the ideal concentration (IC) of 2-Phenoxyethanol (2-Phe) to induce anesthesia for Rhamdia quelen and to compare its effects on stress parameters in R. quelen anesthetized with Eugenol.To accomplish this goal, two assays were carried out.1°) seven 2-Phe concentrations were tested: 300, 400, 500, 550, 600, 650, and 700 µL L -1 to verify IC.When increasing 2-Phe concentrations, induction times decreased while recovery times increased.The IC of 2-Phe to anesthetize R. quelen was 700 µL L -1 (induction 2.98 ± 0.34 min and recovery time 2.75 ± 0.35 min).2°) stress parameters evaluation.Fish were divided into three groups: Control (baseline values, without anesthetic), 2-Phe (700 µL µL L -1 ), and Eugenol (50 mg L -1 ).Levels of cortisol, glucose, and lactate were measured in the fish as indicators of stress at two different times, time zero (T0 = anesthetized) and time one (T1 = one hour after anesthesia).The animals in groups 2-Phe and Eugenol showed a significant increase in glucose values when compared to the control group.The serum lactate at T0 of the Eugenol and 2-Phe groups did not increase when compared to the control group; however, at T1, a significant increase was observed on both anesthetics.No significant differences were found in plasma cortisol levels among the treatments and times.Therefore, 700 µL L -1 of 2-Phe can be considered a suitable anesthetic for R. quelen.