Determination of light sedation concentrations for anesthesia and long-term closed envi̇ronment transfers in Nile tilapia (Oreochromis niloticus) along with stress indicators

This study evaluated the anesthetic and sedative effects of 2-Phenoxyethanol and clove oil on Nile tilapia (Oreochromis niloticus). The fish used in the experiments had an average weight of 36.63 g and an average length of 10.85 cm. To determine the sedation concentrations, deep anesthesia studies were initially conducted, and the identified optimum concentrations were used as references. For both anesthetics, the optimum concentrations that enabled the fish to achieve deep anesthesia within 3 minutes and fully recover within 5 minutes were determined. The optimal concentration was identified as 80 µL/L for clove oil and 800 µL/L for 2-Phenoxyethanol. Following the anesthesia experiments, 24-hour and 48-hour sedation experiments were conducted to evaluate the long-term effects of both anesthetics. These experiments investigated the effects of different concentrations on fish behavior, survival rates, water quality, and cortisol levels. For clove oil, 8 µL/L and 10 µL/L concentrations were found to be the most suitable for prolonged sedation. At these concentrations, fish exhibited calm behavior and high survival rates. For 2-Phenoxyethanol, 105 µL/L was identified as the most effective concentration. Lower concentrations were found to be insufficient for adequately sedating the fish and reducing stress levels. Plasma cortisol levels were analyzed from blood samples collected post-sedation. The lowest cortisol levels were observed in the clove oil group at a concentration of 10 µL/L. In contrast, cortisol levels were generally higher in the 2-Phenoxyethanol groups. These findings indicate that clove oil is an effective and safe anesthetic agent for the sedation of Nile tilapia.