Essential oil of Ocimum basilicum and Eugenol as Sedatives for Nile Tilapia

This study evaluated the modulation of the ventilatory frequency of Nile tilapia sedated with essential oil of Ocimum basilicum and eugenol. The fish were exposed to the following treatments- control (water only); ethanol 200 µl L-1 (concentration used to dilute the anesthetic); eugenol 10 µl L-1 and 20 µl L-1; essential oil of O. basilicum at the concentration of 10 µl L-1 and 20 µl L-1. After 90 minutes of exposure to the treatments, water quality, mortality and respiratory rate were determined. The concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol showed a sedative effect and reduced the excretion of metabolic ammonia in Nile tilapia. There was no mortality in fish exposed to the treatments. The respiratory rate did not differ between the different treatments. It is concluded that the concentration of 20 µl L-1 of the essential oil of O. basilicum and eugenol shows the best result in the inducing sedative effect for Nile tilapia, and that the essential oil of O. basilicum and eugenol in the concentrations of 10 µl L-1 and 20 µl L-1 in an exposure period up to 90 minutes do not alter the ventilatory frequency of Nile tilapia.