Investigation of anesthesic effectiveness of fennel (Foeniculum vulgare miller) and cumin (Cuminum cyminum) essential oils in rainbow trout (Oncorhynchus mykiss)

Anesthetics are widely used in aquaculture. However, some synthetic anesthetics are known to cause side effects in fish. It also causes residues and has negative effects on human health. Therefore, the search for reliable and effective natural products against synthetic anesthetics has increased rapidly. In this study, the anesthetic effects of fennel (Foeniculum vulgare Miller) and cumin (Cuminum cyminum) essential oils on rainbow trout (Oncorhynchus mykiss) were determined by comparing with phenoxyethanol. Rainbow trout with an average weight of 40 g was used in the experiment. In order to determine the anesthetic effect, the essential oils were prepared in concentrations of 10, 20, 50, 100, 150, 200, 300, 400, 500 mg L-1. Anesthesia induction and recovery times were evaluated separately for each fish. In addition, acute toxicity of essential oils on rainbow trout was determined by determination of LC50 concentration in fish exposed to different concentrations of essential oil for 10 minutes. Results showed that induction time decreased with increasing of the concentration of the fennel oil and cumin oil. However, recovery time increased with increasing of the concentration of this anesthetics. 100 mg L-1 dose of cumin essential oil and 400 mg L-1 dose of fennel oil provided deep anesthesia on fish. These concentrations were found to be higher in anesthesia induction and recovery times compared to phenoxy ethanol. These times for cumin 176 and 218.5 sec, fennel 188 and 136.5 sec respectively. 10 and 20 mg L-1 concentrations of cumin and fennel oils showed a sedative effect on rainbow trout. According to acute toxicity test, 10 minutes LC50 concentration (50% death) of cumin oil was 275 mg L-1 . Fennel essential oil, on the other hand, caused only 30 % mortality in fish at the highest concentration tested (600 mg L-1). In the light of these findings, it is suggested that fennel and cumin oils can be used as anesthetics in rainbow trout.