Efficiency of Ocimum basilicum and Eucalyptus globulus essential oils on anesthesia and histopathology of rainbow trout, Oncorhynchus mykiss

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Abstract In this study, anesthetic effects of Ocimum basilicum and Eucalyptus globulus essential oils were investigated on rainbow trout, Oncorhynchus mykiss. Fish (average 10 g) were exposed to 20, 50, 70, 100, 150, 200, 300, 400, 500, and 600 mg L−1 essential oils, anesthesia induction, and recovery times were recorded separately for each fish. Acute toxicities of essential oils (10 min LC50 concentration) on rainbow trout were determined at 70–400 mg L−1. In addition, histopathological effects of the essential oils in fish tissues were determined after deep anesthesia. As a result of this study, O. basilicum at 300 mg L−1 dose and E. globulus essential oils at 400 mg L−1 dose showed ideal anesthetic effects on rainbow trout. Anesthesia induction (stage 4) and recovery times at this concentration for E. globulus were found as 186 and 117.5 s, respectively. Anesthesia induction (stage 4) and recovery times were 220.5 and 61 s for this concentration in O. basilicum essential oil, respectively. The toxic effects of essential oils for rainbow trout were not found. No pathological finding in gill, liver, and kidney was observed at the histopathological examination. Consequently, this study demonstrated that O. basilicum and E. globulus essential oils can be used as an effective and safe anesthetic in rainbow trout.