The northwest Atlantic population numbers about 1.3 million. These seals whelp in the Gulf of St. Lawrence and offshore Newfoundland. After moulting in April, they migrate northward and spend the summer around Greenland and in the eastern arctic islands of the Northwest Territories. The southward migration begins in September. The harp seal's diet is primarily marine fish and crustacean macroplankton.
Young seals feed in the surface waters while adult harps dive deeper for cod and herring.
One seal consumes about 450 kg of fish annually, arctic cod being their most important food. Intense feeding occurs during summer and winter while less feeding occurs during spring and fall migration, whelping and moulting. The few predators that take harp seals are polar bears, killer whales, sharks and humans. Other causes of mortality are decreases in food by large scale capelin fisheries, discarded netting, and oil pollution. Harp seals are very vocal on the breeding and whelping grounds.