During laboratory and field experiments in Ontario, with hatchery muskellunge 90–235 mm in total length, total removal of a fin did not add to the immediate mortality caused by seining the fish from ponds. The use of an anesthetic during surgery (MS-222) did not affect subsequent survival of marked, stocked fish. Removal of any single paired fin was equally detrimental to short-term (3 months) survival. In contrast, over long periods (10 months) the loss of a pectoral fin was more detrimental than loss of a pelvic fin. Removal of both fins of a pair may cause higher mortality than the removal of one fin. Neither the fin removed nor the anesthetic significantly affected short-term or long-term growth. Within 1 year of marking regeneration of amputated fins was such that recognition of marked fish was difficult and the degree of difficulty increased with time. Estimates based on marked 2-year-old or older individuals could result in substantial underestimates of survival.