Section 529.2503 - Tricaine methanesulfonate(a)Specifications. The drug is ethyl-m-amino-benzoate methanesulfonate.(b)Sponsor. See Nos. 050378 and 051212 in § 510.600(c) of this chapter.(c)Conditions of use -(1)Amount. It is used as follows:(i)Fish. The drug is added to ambient water at a concentration of from 15 to 330 milligrams per liter depending upon the degree of anesthetization or sedation desired, the species and size of the fish, and the temperature and softness of the water. Preliminary tests of solutions must be made with small numbers of fish to determine the desired rates of sedation or anesthesia and the appropriate exposure times for the specific lots of fish under prevailing conditions.(ii)Amphibians and other aquatic coldblooded animals. The drug is added to ambient water in concentrations of from 1:1000 to 1:20,000 depending upon species and stage of development.(2)Indications for use. For the temporary immobilization of fish, amphibians, and other aquatic coldblooded animals (poikilotherms) as an aid in handling during manual spawning (fish stripping), weighing, measuring, marking, surgical operations, transport, photography, and research.(3)Limitations. Do not use within 21 days of harvesting fish for food. Use in fish intended for food should be restricted to Ictaluridae, Salmonidae, Esocidae, and Percidae, and water temperature exceeding 10 °C (50 °F). In other fish and in coldblooded animals, the drug should be limited to hatchery or laboratory use. 79 FR 10974 , Feb. 27, 2014