Migration of the “Northern” Atlantic Cod and the Mechanisms Involved

Abstract

Northern (Labrador-eastern Newfoundland shelf) Atlantic cod (Gadus morhua) spawn in March-June at depths in excess of 250 m and at bottom temperatures near 3 C. The eggs develop as they drift in the Labrador Current to shallow nursery grounds 600–1,000 km to the south. Spent adults also move southward and westward toward the coast of Labrador and Newfoundland, perhaps homing to the same areas where they grew up. The shoreward migration, through a layer of colder (-1.5 to 0 C) water, may be guided by migrating capelin (Mallotus villosus) on which the cod feed. Adults are joined by fish maturing for the first time in a fall migration back to the spawning grounds. Better understanding of these extensive migrations requires research on the factors that trigger migratory activity and guide the migrations. Particularly appropriate are studies of endocrine involvement in the cod’s migratory responses, the role of capelin in the shoreward migration of cod, and movements of tagged and telemetered cod in relation to thermal fronts and stratification in the water column.