Anesthetic responses of the neotropical catfish pacamã (Lophiosilurus alexandri) to the essential oil of Lippia alba

Essential oils have been used in aquaculture as natural anesthetics in an effort to reduce stress in animals during activities such as handling, biometrics, and transport. In this context, the anesthetic effect of the essential oil of Lippia alba (EOLA) in juvenile of pacamã (Lophiosilurus alexandri) was tested. Eighty juveniles weighing 10.41 ± 2.01 g and measuring 9.99 ± 0.85 cm in length were subjected to an anesthesia test. The time required for induction of anesthesia was assessed using eight 2-L beakers, one of which served as the control and contained water with the same amount of alcohol used to dilute the highest concentrations of EOLA, and seven beakers with different concentrations (50, 75, 100, 125, 150, 175 e 300 mg L⁻¹). 10 juveniles were used for each concentration. Another eight 2-L beakers containing only clean water were used to determine the recovery time from anesthesia. The induction time was determined when the juvenile showed a loss of balance, while the recovery time was determined by the return of this response. Adequate anesthesia in fish is considered up to 3 min for sedation and up to 5 min for recovery. The induction time in this study exhibited a quadratic effect (R² = 0.87), remaining below 180 seconds at concentrations of 125 mg L⁻¹ and above. The recovery time showed no correlation with increasing EOLA concentrations, remaining below 60 s for all concentrations tested. It is concluded that EOLA at concentrations between 125 and 300 mg L⁻¹ can be used to anesthetize L. alexandri. Financial support: Funded by Dr. Bruno Bello Vicintin in partnership with Rima Industrial S/A