Many seal species depend on the same species of fish as are utilized by man. The rapid development of intensive fisheries in many parts of the world, leading to high catches of such species, threatens the food supply of certain seal species, preventing the maintenance of reasonable population levels, whether or not these seals are exploited by man. Because such seals have habits inimical to fishing interests (consumption of fish, damage to nets, hosts to fish diseases), there is considerable commercial pressure to maintain seal populations at levels below their natural size, leading to the risk of local extirpation. Seals are also threatened by marine (and particularly oil) pollution and the modification of estuaries for water storage. Human activity on seal hauling-out grounds which will increase with tourism, and particularly disturbance of nursing mothers and their young, can cause significant mortality among seal populations.
Indiscriminate killing of seals, whether for pelts or to protect fishing grounds, would soon reduce their numbers sharply and perhaps jeopardize their existence. This was demonstrated in the late 19th century when the herds of fur seals in the North Pacific, whose numbers in the 1860s had reached almost 2,000,000 fell to about 200,000 in 1911 after commercial hunters had relentlessly pursued them. As a result of protection their numbers rose again to 1,600,000 in 1941.
1 possibly endangered species; 1 rare sub-species.
Perhaps the greatest danger to seals at the present time is pollution of marine habitats which is causing a decrease in their ability to fight off infections. About one half of the European seal population died of a form of distemper because of their weakened condition from living in the highly polluted North Sea.
Seal penises are used in traditional Chinese medicine as an aphrodisiac and the popularity of this mythical sexual stimulant encourages the unregulated hunting of seals, including protected species. The species involved in the seal penis trade include harp seals hunted by Norway in the northeast Atlantic, Cape fur seals from Namibia, South American fur seals in Uruguay, northern fur seals in the USA, and harp and hooded seals from Canada. The size and value of the trade in seal penises is unknown, but is believed to be lucrative and growing. A Chinese syndicate reportedly offered to buy 60,000 seals in Labrador and Newfoundland in 1993, and another company subsequently offered to buy and process 250,000 seals. In 1994, fishermen on the Galapagos Islands killed an undetermined number of Galapagos sea lions, a small population numbering 30,000-40,000 and sent a consignment of their penises to Japan.