Eugenol (4-allyl-2-methoxyphenol) was found to exhibit an anesthetic effect on various fishes.
Carp, Cyprinus carpio, medaka, Oryzias latipes, crucian carp, Carassius auratus and rainbow trout, Salmo gairdnerii irideus were anesthetized in a short time in water containing 12.5 to 100 ppm of eugenol as added to water in the form of FA-100 (a pharmaceutical preparation of 10% eugenol). Eugenol was effective at only one fourth the concentration of MS-222 that would give comparable effects in gold fish, Carassius auratus, medaka and crucian carp. Anesthesia by FA-100 and recovery from it required longer time at low water temperatures (5 and 10°C) than at normal temperature (24.5°C).