Grey seals, once practically eliminated from the western Atlantic, have made a tremendous resurgence along the east coast of the USA since the initiation of the Marine Mammal Act of 1972.
There are two thriving grey seal populations in the Atlantic: one in the northeast and one in the
northwest, and there are several pronounced differences between these populations. First, in the east, pups are born in autumn while in the west they are born in winter. After birth, pups retain their soft white fur for a month until they shed it to grow a thick, grey, waterproof coat. At this point in their lives, they venture into the sea and begin to fend for themselves, spending most of their time in the water. Grey seals haul out onto the shore during breeding, molting and copulation.
Grey seals from the Western Atlantic are on average larger than gray seals from the East, with males reaching up to 880 pounds and females reaching 550 pounds. They maintain this weight on a diet consisting of mainly fish, as they have the ability to dive down to 70 meters. Contrary to popular perceptions, it is unlikely that grey seals were responsible for the cod stock collapse in the North Atlantic because they are opportunistic feeders, eating a variety of meat that includes small cetaceans, seabirds, crustaceans and cephalopods. Current research does not support the idea that the grey seals preferentially ate cod. The collapse was most likely due to commercial overfishing in the North Atlantic.
Grey seals congregate in several colonies in the Eastern Atlantic, mainly around the United Kingdom and Ireland. In the Western Atlantic, Grey seals are found in the coastal Canadian waters all the way south to New Jersey. Sabel Island, located in this range, is the largest grey seal population in the world.