Investigation of the use of thymol and carvacrol as anesthesic substance in kangal fish (Garra rufa)

This study was carried out to determine the anesthetic effects of thymol and carvacrol anesthetic agents on Kangal fish, Garra rufa at 25 °C water temperature. Five different thymol (25, 50, 75, 100 and 150 mg L-1) and carvacrol (25, 50, 75, 100 and 150 µL L-1) concentrations were studied. The effect of concentration of both anesthetic agents on induction and recovery time of fish were determined. Ten fish were used for each anesthetic concentration in the experiment. Results indicated that all the tested thymol and carvacrol concentrations were found to have anesthetic effect on Kangal fish. All thymol and carvacrol concentrations were effective in promoting anesthesia and recovery, and no mortality was observed during the anesthesia experiments and for 24 h afterwards. The lowest effective anaesthetic concentrations of thymol and carvacrol determined were 50 mg L−1 (129.7 ± 28.3 s) and 50 µL L-1 (145.3 ± 20.9 s), respectively. The thymol and carvacrol concentrations of 50 - 150 mg or μL L−1 resulted in induction times (Stage 2) less than 180 s. Tymol and carvacrol concentrations significantly affected all anesthetic induction and recovery times (P<0.05). Induction times (Stage 1 and Stage 2) negatively correlated with the thymol and carvacrol concentrations. Recovery time (Stage 2) for thymol and carvacrol ranged from 268.8 ± 33.7 to 508.2 ± 62.6 and 234.2 ± 26.3 to 361.8 ± 65.3, respectively. As a result, optimum anesthetic concentration values on Kangal fish were found to be 50 mg L-1 for thymol and 50 µL L-1 for carvacrol. 100 and 150 mg L-1 thymol, 100 and 150 µL L-1 carvacrol can be used for rapid anesthesia in aquaculture procedures such as blood draw. In addition, it is thought that further work is also necessary to evaluate the physiological effects of thymol and carvacrol on Kangal fish.