LAUSR

Abstract In this study, we determined the effects of clove oil concentration and water temperature on the anesthesia and recovery times, hematological factors, and physiological responses in the olive flounder (Paralichthys olivaceus). To determine these times at three temperatures (17, 21, and 25 °C), fish (mean length [± standard deviation]: 30.0 ± 1.0 cm, mean weight [± standard deviation]: 245.0 ± 27.1 g) were exposed to clove oil at concentrations of 40, 80, 120, 160, 200, 240, and 280 mg L−1. At 0.5, 1, 3, 6, and 24 h, blood samples were collected from 10 fish in the 160 mg L−1 clove oil-treated group (AG) and the non-anesthetic group (NAG) maintained at 21 °C. Subsequently, the following parameters were analyzed: hematocrit and hemoglobin levels; red blood cell count; osmolality; cortisol, glucose, lactic acid, Na+, K+, and Cl- concentrations; and aspartate aminotransferase and alanine aminotransferase activities. Clove oil concentration and temperature exhibited interdependent effects on the anesthesia and recovery times. As the water temperature increased, the anesthesia and recovery times decreased, and as the clove oil concentration increased, the anesthesia time decreased and recovery time was prolonged. AG showed significantly higher plasma cortisol and glucose concentrations than those of NAG at 0.5 and 1 h after anesthesia, but significantly lower concentrations than those of NAG at 24 h after anesthesia. In addition, the lactic acid concentration in AG was lower than that in NAG at 0.5, 1, and 3 h. Intergroup differences for all other blood factors and osmolality were not significant before or after anesthesia. Based on stage III behavior, the anesthesia and recovery times should be less than 180 and 300 s, respectively, to prevent hypoxia in fish under anesthesia. Therefore, the stable anesthesia concentrations for olive flounder (245.0 ± 27.1 g) were 120–160 mg L−1 at 21 °C and 80–240 mg L−1 at 25 °C. Moreover, as 18–21 °C was determined to be the optimal water temperature for olive flounder rearing (˜245.0 g), we suggest that as an optimal anesthetic, clove oil can be optimally used at 160 mg L−1 concentration at 21 °C and that it is a reasonable alternative to other anesthetics.