Effects of Tagging on the Growth of Cod

Abstract Atlantic cod were tagged and liberated at sea. Length data from recaptured individuals were examined for growth. Cod marked with Lea tags anchored internally grew at about the same rate as those marked with Petersen discs attached dorsally. The tagged fish grew at about the same rate as untagged fish. The results suggest tagging has little effect on cod growth and are confirmed by reports of cod tagged in aquaria. This is in contrast, however, to reports of other species—freshwater and marine—in which tagging markedly changed their growth rate. The possible reasons for changes in growth of tagged fishes are discussed.