Background. Assessments of the efficacy of anaesthetics are usually based on observations of fish behaviour or changes in blood parameters. In this study we attempted to assess the process of anaesthesia, caused by 2-phenoxyethanol and Propiscin (0.2% etomidate), based on recording the heartbeat and the respiratory frequency. Materials and methods. The effect of two concentrations of 2-phenoxyethanol (0.4 mL·L–1 and 0.8 mL·L–1) and two concentrations of Propiscin (1.0 mL·L–1 and 2.0 mL·L–1) on heartbeat and respiratory frequency of common carp, Cyprinus carpio L., were studied using ECG. Concurrently, during general anaesthesia, the fish behaviour was also observed. Results. The anaesthetic potential of 2-phenoxyethanol and Propiscin at the applied concentrations was comparable. The behavioural reactions caused by the agents were not identical. At the beginning of the exposure, 2-phenoxyethanol produced locomotor agitation and an irritation-like reaction of the respiratory system. Propiscin had no such effect. Both agents induced a decrease in the ventilatory and cardiac frequencies. The reductions caused by Propiscin were simultaneous. The inhibitory effect of 2-phenoxyethanol at the concentration of 0.8 mL·L–1 was much stronger on respiration than on heart rate. Conclusion. The ECG method can be an important and objective tool supplementing data acquired during visual observation of responses to anaesthesia. Its major advantage is the comparativeness of data.

2-phenoxyethanol, Propiscin, anaesthesia of fish, common carp