Background. Clove oil, containing the active ingredient eugenol, has been reported to be an inexpensive and effective fish anaesthetic. The objective of the presently reported study was to establish the lowest effective concentration of clove oil for the common carp, Cyprinus carpio L., and safe working ranges for the anaesthetic. Materials and methods. Carp were exposed to the concentrations of 10, 20, 30, 40, 50, 100, 150, and 200 mg • L-1 of clove oil. The onsets of individual phases of anaesthesia and recovery rates were studied. In experiment 1 the fish were held in the anaesthetic bath until the lack of responses to handling was observed and in experiment 2—until the fading of ventilation. Results. Clove oil at the concentrations ranging from 30 to 200 mg • L-1 induced general anaesthesia. The lowest concentration causing general anaesthesia with an average induction time below 3 min was 40 mg • L-1. Recovery was concentration-independent and lasted for about 4 min (experiment 1). An increase in the concentration shortened the time of ventilation during anaesthesia and prolonged the recovery (experiment 2). Conclusion. Clove oil is a potent anaesthetic for carp, the safest and most effective at the concentrations of 30-50 mg • L-1. Therefore those solutions should be used, in the aquaculture practice, when the procedure requires more than 5 min of the exposure to the anaesthetic.

clove oil, eugenol, anaesthesia, common carp, Cyprinus carpio, fish