Sealing became a popular pursuit for the whaling fleet. Harp seals, which basked on the ice floes in huge numbers during the spring were shot and taken for their blubber oil and skins. The gregarious females give birth to a single pup on newly formed pack ice in mid-February to April, depending upon location. The young are fed on rich milk for c. 12 days during which time they grow from 11 to 38 kg.

In 1852 captain Sellar of the whaler Agostina took 9852 seals. With 22 ships from Peterhead alone at the sealing that year it is not hard to see why seal numbers rapidly declined in the second part of the century.

In 1876 Captain David Gray reported "twenty years ago a pack of seals would have extended in every direction as far as could be seen. Now a pack rarely exceeds a twentieth part of the size."