Efficacy of fennel (Foeniculum vulgare) and anise (Pimpinella anisum) essential oils as anaesthesics in common carp (Cyprinus carpio L. 1758)

In this study, the anaesthetic effects of fennel and anise essential oils were investigated on common carp. Fish (10 ± 0.45 g) were exposed to nine concentrations of essential oils (5, 10, 20, 50, 100, 200, 300, 400 and 500 mg L^-1). Additionally, the histopathological effects on the fish tissues including gill, skin and hepatopancreas and physiological effects on some blood parameters (Na⁺, K⁺, Ca⁺², Cl^-, total plasma protein and glucose) of essential oils were investigated in carp. At the end of the experiment, fennel oil showed an anaesthetic effect at a concentration of 500 mg L^-1 in carp (anaesthesia induction and recovery times were 308 and 472 s, respectively). Anise essential oil showed deep anaesthesia at a concentration of 100 mg L^-1, but anaesthesia induction time was found to be very long (20 min). In addition, anise oil at concentrations above 100 mg L^-1 caused 10% mortality in fish. Blood parameters except glucose level in both essential oils were unchanged during deep anaesthesia in carp. However, plasma glucose levels were found lower in fish anaesthetized with anise oil than control and fennel groups (P < 0.05). At the histopathological examination, no pathological findings were observed in any organ of fish in the fennel group. However, severe hyperemia and inflammatory cell infiltrations in gills, erosive lesions in the skin and slight inflammatory reactions in the skin were observed in the anise group. The present study demonstrated that fennel essential oil at 500 mg L^-1 concentration can be used as an effective and safe anaesthetic in common carp, but anise essential oil is not suitable.