Anaesthetic efficacy of eugenol in doctor fish (Garra rufa): Behavioural and cardiovascular responses

The effects of eugenol anaesthesia on the behavioural and cardiovascular responses of doctor fish (Garra rufa) (2.0 +/- 0.2 g mean weight) were studied. Two experiments were performed. In experiment 1, G. rufa was exposed to eugenol baths at different concentrations (0, 12.5, 25, 50, 75, 100 and 150 mu l/L) to record induction and recovery times and fish behavioural responses. Experiment 2 was performed to evaluate the effects of different eugenol concentrations (50, 100 and 150 mu l/L) on the electrocardiographic parameters of anaesthetized fish. Induction and recovery times were recorded for each fish separately, and 10 fish were used per eugenol concentration. During the induction stage, video recordings were taken to evaluate fish behaviour. Thereafter, electrocardiographic (ECG) records were taken with the help of electrodes attached to the anaesthetized fish. A strong relationship between eugenol concentrations and induced anaesthesia was verified (R-2 = 0.8583), but this relationship decreased slightly during recovery time (R-2 = 0.6481). Distance movement, movement duration, swimming speed (velocity) and mobility significantly decreased with an increase in eugenol concentration. ECG results indicated that G. rufa had higher heart rates when anaesthetized with a high concentration of eugenol than with a low concentration (150 mu l/L, 94.4 +/- 7.3 beats/min; 50 mu l/L, 69.0 +/- 3.7 beats/min). The QT interval was significantly higher for G. rufa anaesthetized with 100 and 150 mu l/L eugenol concentrations. In conclusion, 25 and 50 mu l/L eugenol concentrations can be used for general aquaculture procedures in G. rufa, and 75 mu l/L is suitable for rapid blood sampling.

Automated summary

The effects of eugenol anaesthesia on the behavioural and cardiovascular responses of doctor fish (Garra rufa) were investigated. The results showed a significant relationship between eugenol concentration and induction of anesthesia, but this relationship weakened slightly during the recovery phase. Increased eugenol concentration led to a decrease in distance movement, movement duration, swimming speed, and mobility. The electrocardiographic results demonstrated that higher eugenol concentrations resulted in higher heart rates and longer QT intervals for the anaesthetized fish.