Caspian seal

Caspian seal, (Pusa caspica), species of small earless seals that inhabits the waters, islands, and coastal areas of the Caspian Sea. It is the only mammal that lives in the Caspian Sea, which is a saltwater lake. Adults range in length from 1.4 to 1.8 meters (4.6 to 6 feet) and weigh about 55 kg (120 pounds), making them some of the smallest living pinnipeds. The Caspian seal is classified in the family Phocidae with the ringed seal (Pusa hispida) and the Baikal seal (P. sibirica).

Natural history

There is very little size difference between the sexes. However, males and females can be distinguished from one another by their coloration and spot pattern. Although the fur of both sexes ranges from charcoal gray to grayish yellow, both sexes have light-colored undersides. Males have conspicuous dark spots throughout their coat (including their undersides), whereas females have lighter spots that are limited to the dorsal side. Pups average about 70 cm (28 inches) in length and about 4 kg (9 pounds) in weight at birth; they have long fur (lanugo) that is white to silver-gray.

Caspian seals spend the winter months on the ice that forms in the northern Caspian Sea and the summer months in the warmer waters of the sea’s southern reaches. Although the seals are fish eaters, their diet changes with the seasons. During the winter they tend to consume sculpins and gobies. During the summer, however, their food choices expand greatly to include kilka (Caspian Sea sprat [see bristling])—which forms nearly 70 percent of their diet—herring, sturgeon, and smelt as well as mollusks and other invertebrates. Unlike Baikal seals, which dive as deep as 400 meters (1,300 feet) in search of food, Caspian seals typically dive only as deep as 50 meters (164 feet). Wolves and eagles are the seals’ primary natural predators. In addition, every year, some 18,000 seals are legally killed by hunters, who harvest the seals’ blubber and lanugo, and an estimated 12,000 more seals are captured accidentally as bycatch in fishing nets.

Having noted an absence of infighting among breeding adults and competition for mates, several sources report that the species is monogamous. Caspian seals breed once per year, between late February and mid-March, in polynyas (areas of open water surrounded by sea ice) in the northern Caspian Sea. After an 11-month gestation period, a single pup is born on the sea ice sometime between late January and early February the following year. Although sources note that females nurse their pups for up to five weeks, parental care among Caspian seals beyond this period is not well studied, and adult females often go off to breed again directly after weaning their offspring. Young Caspian seals shed their lanugo and develop their adult fur starting in April, which allows them to enter the water and swim to the warmer, southern parts of the sea for the summer. Females become sexually mature as early as age 5 and males at age 6 or 7. Caspian seals can live up to 50 years in the wild.

Conservation status

Since 2016 the Caspian seal has been classified as an endangered species by the International Union for Conservation of Nature and Natural Resources (IUCN). Population surveys estimate that 68,000 adults remain. The seal is beleaguered by several threats. Hunting decimated the Caspian seal population during the 20th century, but, in the 1960s and 1970, countries bordering the Caspian Sea instituted a variety of hunting quotas and other regulations (such as those that forbid the taking of female seals on breeding grounds). Since then other threats to seal populations have emerged. Seals are caught in nets as bycatch in sturgeon fisheries, and periodic outbreaks of canine distemper virus have plagued the seals since the 1990s. In addition, fish populations have declined because of increased pressure from commercial fishing, water pollution, and an invasion of comb jellyfish, which compete with the seals’ prey by eating zooplankton.

Although countries that border the Caspian Sea have devised recovery and management plans to help with the seal’s conservation, such measures are inconsistent and not legally binding across the region. Since the 2010s Kazakhstan has become more proactive in deterring illegal sturgeon fishing, which may provide the seal with more food resources and reduce the risk of its becoming bycatch. In addition, several coastal fishing communities in Iran have increased efforts to free Caspian seals entangled in nets and rehabilitate injured animals rather than simply euthanizing them.