Distinguishing small juvenile Atlantic cod (Gadus morhua) from Greenland cod (Gadus ogac) by comparing meristic characters and discriminant function analyses of morphometric data

Two biochemical, 7 meristic, and 14 morphometric characters in addition to total body mass were examined to determine which characters best distinguis h demersal Gadus ogac from Gadus morhua over the size range 87-135 mm stand ard length. These congeneric species of cod (Gadidae) remain difficult to d istinguish where they co-occur in coastal habitats as recently settled juve niles. Consequently, surveys that target young demersal cod (G. morhua)in c oastal nursery areas may be biased, owing to misidentifications. The electr ophoretic mobilities of esterase and creatine kinase proteins unambiguously distinguished G. ogac from G. morhua. Of the 14 morphometric characters ex amined by means of discriminant function analyses, eye diameter and body de pth at the origin of the second dorsal fin in addition to total body mass b est separate G. ogac from G. morhua over the size range examined. In genera l, G. ogac has smaller eyes and is heavier and deeper bodied than G. morhua . Counts of vertebrae and of dorsal, anal, and caudal fin rays overlap betw een species. The shape of the lateral line and especially body coloration a re additional characters that help to distinguish these species in the fiel d. Gadus ogac are usually bottle green when freshly caught, whereas G. morh ua are usually brownish in dorsal and lateral coloration. Gadus ogac also o ften have a more strongly arched lateral line than G. morhua of a similar s ize. All juvenile cod collected along the northeast coast of Newfoundland i n this study were either G. ogac or G. morhua. Microgadus tomcod, another g adid common in coastal habitats, was not collected.