Evaluation of the Anesthetic Effects of Eugenol with Varying Ratios of Eugenol to Ethanol in Killifish (Fundulus heteroclitus)
Recently, there has been increased interest in alternative methods for sedating and anesthetizing fish. Clove oil has become a popular choice among fish hobbyists and commercial fish farmers.1,2 The anesthetic agent under investigation is a pharmaceutical grade of clove oil (Sigma Co., 100% eugenol). Eugenol is highly insoluble in water and is prepared for addition to water through the addition of ethanol. There have been few controlled studies on the use of eugenol as an anesthetic in salt-water fish and even fewer on proper dosing protocols. This study compared the efficacy of eugenol as an anesthetic agent at varying ratios of eugenol to ethanol in the killifish (Fundulus heteroclitus). This study compared the effects of eugenol preparations of 1:9 eugenol in ethanol, 1:1 eugenol ethanol, and 9:1 eugenol in ethanol on the anesthetic properties of the compound when administered to F. heteroclitus. Two control groups were utilized in this study. The first was a treatment group in which the fish were exposed to plain tank water in the experimental setup and their behavior and respiratory rates recorded. The second control in this experiment was to add 95% ethanol to tank water as a second trial group to observe what effect the ethanol may be having on the killifish. The final concentration of eugenol in test water was held at 25 mg/L of eugenol in the tank water for the trial groups 1,2, and 3. For this experiment, 50 killifish were randomly divided into five trial groups and were individually exposed to test water. The test water consisted of 1:9 eugenol in ethanol for trial one, 1:1 eugenol in ethanol for trial two, 9:1 eugenol in ethanol for trial three, and an equal volume of ethanol for trial four as used in the eugenol mixture from trial one. Trial five killifish were exposed to plain tank water in the same experimental setup as used for trial groups 1–4. For each fish, respiration rates were recorded prior to anesthetic exposure, at 1-min increments following exposure to test water up to 10-min post-exposure, and at 1-min increments following placement in recovery water. In addition, time to maximum anesthetic effect and time to recovery were calculated for trial groups experiencing anesthetic induction. The degree of anesthetic depth was estimated through observational methods using an anesthetic staging scheme.
The authors of this paper would like to thank the following members of the fish and invertebrate aquarists of the husbandry department at the Mystic Aquarium for the collection and care of the animals used in this experiment: Greg Charbeneau, Cathy Ellis, Jan Drugge, Kristin Lomme, Dan Augustino, Nicole Grandinetti, Richard Pierce, David Smith, and Stewart Schenck. We would also like to thank Gayle Sirpenski for their help in coordinating this project and externship. Special thanks to Carrie Goertz for her help in the setup of this experiment.
1. Anderson W.G., R.S. McKinley, and M. Colavecchia. 1997. The use of clove oil as an anesthetic for rainbow trout and its effects on swimming performance. N Am J Fish Manag. 17:301–307.
2. Soto C.G. and G. Burhanuddin. 1995. Clove oil as a fish anaesthetic for measuring length and weight of rabbitfish (Siganus lineatus). Aquaculture. 136:149–152.