In 1994, the population was increasing at an average rate of 5 per cent a year, or about 250,000 seals. Harp seals migrate every year between Arctic and sub-Arctic regions of the North Atlantic. There are three stocks in the North Atlantic, the Northwest Atlantic population being the largest. These seals migrate to areas off eastern Newfoundland and in the Gulf of St. Lawrence where they give birth in late February or March. Following the moult in April and May, the harp seals return north to summering areas in the Canadian Arctic and off Greenland.
Adults are difficult to count because many are underwater at any one time.
However, pups remain on the ice during the whelping period, making it possible to estimate their total number. Aerial surveys in March 1994 provided an estimate of 703,000 pups. From these numbers, scientists are able to calculate the total population of seals. Each harp seal, on average, eats 1.4 tonnes of prey a year. Scientists analyzed the contents of stomachs and took into account locations, energy requirements, and diet by age, population and season.