Variant colourations of Atlantic cod (Gadus morhua) in Newfoundland and Labrador nearshore waters

Abstract

Adult cod (Gadus morhua) inhabiting continental shelf waters of the Northwest Atlantic typically display a countershaded colouration: a dark back gradating to a light underbelly. Some cod in Newfoundland and Labrador inshore waters have predominantly brown or red pigmentation. Cod inhabiting Gilbert Bay in Labrador often have golden-brown colouration, likely the result of an invertebrate diet rich in carotenoids, and are known in the vernacular as the “golden cod of Labrador”. To determine the stability of these variant colourations, we captured cod from Gilbert Bay, held them in a net pen and fed them a diet of fish. Over the 12-week experimental period, the variant coloured cod lost much of their brown or red pigmentation, and became countershaded. Because of its impermanence when cod switch from invertebrate to fish prey, variant colouration of cod can provide only provisional information about stock origin.