There may be times when you need to anaesthetise fishes. Some of these may include ease of handling for providing medication, vaccinations and for grading. Anaesthetics may also be used as a humane way to euthanise or harvest fish. So what can you use to do all these?
Iso-eugenol (a derivative of eugenol, which is present in clove oil) is marketed as Aqui-S and can be obtained through your veterinarian. It was initially formulated for use in aquacultured fishes with no witholding period for human consumption. It can also be used off label for a variety of other fishes, including your pet fish. The abstract below evaluates the efficacy and safety of the product as it relates to koi fish.
Evaluation of isoeugenol for anesthesia in koi carp (Cyprinus carpio)
Dr. Gladden’s present address is Florida Veterinary Specialists, 3000 Busch Lake Blvd, Tampa, FL 33614.
Supported by the Pamela De Journo Endowment Fund.
Presented in abstract form at the Annual Conference of the American Association of Zoo Veterinarians and Association of Reptilian and Amphibian Veterinarians, Los Angeles, October 2008.
The authors thank Suzette Knight, Melissa Christian, Jason Norman, Dr. Pam Govett, Abby Farakesh, Sara Smiley, Chrissie Shoemaker, Heather Bjornebo, Dustin Haskins, Andrew Baxter, Allen Pattillo, Krista Woodward, Russell Parr, Trey Dunn, Raj Joshi, Gretchen Singletary, Claire Erlacher, Hollis-Ann Stewart, Shannon South, Audra Jean Henderson, Jessica Casto, and Luke Williams for technical assistance and Dr. Deborah Keys for statistical assistance.
Objective—To evaluate isoeugenol as an anesthetic agent in koi carp.
Animals—216 juvenile koi carp (Cyprinus carpio).
Procedures—Fish were randomly allocated to 9 groups of 24, and each group was randomly exposed to isoeugenol concentrations ranging from 0 to 500 mg/L. General activity, excitement, fin and gill color changes, opercular movement rate, loss of equilibrium, muscle tone, jaw tone, and handleability were assessed. Five fish from the control (0 mg/L), 200 mg/L, and 500 mg/L groups were randomly selected prior to anesthetic recovery and again 24 hours after recovery for euthanasia, gross necropsy, and histologic assessment of gills, internal viscera, and skeletal muscles.
Results—Mean ± SD interval to achieve stage 2 anesthesia with isoeugenol ranged from 22.4 ± 6.2 minutes at 20 mg/L to 0.25 ± 0.4 minutes at 500 mg/L, whereas the mean interval to stage 3 anesthesia ranged from 28.1 ± 3.9 minutes at 20 mg/L to 0.33 ± 0.48 minutes at 500 mg/L. With the exception of the 500 mg/L group, opercular movements were maintained throughout. Death was observed only in the 500 mg/L group, in which 50% of the fish either failed to recover or died within 24 hours after anesthetic exposure. There were no pathological differences between fish exposed to isoeugenol at 0 or 500 mg/L.
