Station de recherche en pêche et Aquaculture continentales (SRPAC), Laboratoire d’Ichtyologie et de Conservation des gènes de poissons, Centre National de Recherche Agronomique (CNRA), Bouaké, Côte d’Ivoire
The anesthetic effect of clove essential oil and 2-Phenoxyethanol on tilapia Oreochromis niloticus is evaluated. For this study, 200 specimens measuring 103 to 169 mm SL and weighing 29 to 135 g were collected from ponds at the CNRA continental fishing and aquaculture research station in Bouaké and stored at 27°C in two thermostatically controlled tanks supplied by a closed water circuit. These specimens were fed with the ternary compound food 3A, at a rate of 110 g/d. After one week of acclimation, the fish were kept fasting for 30 h before the experiment. For the anesthesia tests, a device of three tanks was used per anesthetic, one for the control solution (Water + 90% Ethanol), one for the anesthesia and one for waking up the fish. The doses tested are 0.02, 0.04 and 0.06 ml/L of water for clove oil and 2.5, 5 and 10 ml/L of water for 2-Phenoxyethanol. Clove oil is previously dissolved in a solution of water and ethanol at a rate of 0.02 ml for 4 ml of ethanol/L of water. A control test without anesthetic was also carried out with the Water-Ethanol solution, in order to highlight the effect of Ethanol. The results obtained show that clove oil has a higher anesthetic power on O. niloticus compared to 2-Phenoxyethanol. The optimal effective dose is 0.04 ml/L of water compared to 0.5 ml/L of water for 2-Phenoxyethanol. The respective time of total loss of reflexes fluctuates between 31 s and 1 min 56 s for the first anesthetic, compared to 1 min 36 s to 4 min 08 s for the second at the minimum doses indicated. Ethanol has no anesthetic power on O. niloticus. The availability of clove oil on the local market in naturotherapist pharmacies and its affordable cost, i.e. 15,000 CFA francs for a 100 ml dose, make it a good candidate for the anesthesia of O. niloticus in aquaculture farms.