Caspian seal (Pusa caspica)

Synonyms: Phoca caspica
GenusPusa (1)
SizeMale length: up to 150 cm (2) (3)
Female length: up to 140 cm (2) (3)
Weightup to 86 kg (2) (3)

Classified as Endangered (EN) on the IUCN Red List (1).

One of the smallest of all seals (4), the Caspian seal is unusual in being confined to the inland, entirely landlocked Caspian Sea (1) (2) (3) (5) (6), the largest enclosed body of water on earth (7). The coat of the Caspian seal is greyish-yellow to dark grey above, with a lighter grey belly and sides, and irregular dark spots on the back. The male is slightly larger than the female, and has darker spots, while pups are born with a long, white, woolly coat, known as ‘lanugo’, which is replaced after about three weeks with short, dark grey hair (2) (3) (5) (6) (8).

The Caspian seal is endemic to the Caspian Sea, an inland sea bordered by Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. Seasonal migrations, prompted by ice formation, occur between the northern, southern and middle regions of the Sea (1) (3) (4) (6) (8).

The Caspian Sea has no connection to the oceans, and its waters are only weakly saline (7) (9). The Caspian seal uses both the shallow northern basin of the Sea and its deeper middle and southern waters, as well as sometimes entering the rivers which feed the Sea. Births usually occur on ice that forms in the north, although sandy islands, sand banks and reefs are also used for giving birth and for hauling out (1) (2) (4) (6) (8).

The Caspian seal feeds on a variety of small fish, particularly kilka (Clupeonella species), as well as crustaceans such as shrimp (1) (2) (6) (8) (10). The diet may vary seasonally (3), and seasonal migrations may be driven in part by prey abundance (2). In turn, adults and pups may be vulnerable to predators such as wolves and large eagles (1) (8) (10).

Groups of female Caspian seals tend to gather around cracks in the ice to give birth, or maintain small access holes near the breeding site (1) (2) (6) (8) (9). A single young is born after a gestation of about 11 months, a period which is likely to include several months of delayed implantation. The newborn Caspian seal weighs just five kilograms, and is nursed for around a month (1) (2) (3) (6) (8), but does not enter the water until after the lanugo coat has been moulted and the ice has started to melt (1) (9). About a month after the pups are born, from late February to mid-March, the male Caspian seals arrive at the breeding colony to mate with the females (2) (3) (5) (8) (9), after which the ice breaks up, the adults moult, and the seals start to disperse south into deeper, cooler areas to feed (1) (2) (8) (9). The Caspian seal reaches maturity between about 4 and 7 years (2) (5) (6) (10), and may live for around 35 years (6) (10) (11), or exceptionally up to 50 (2) (8) (11).

Believed to have numbered over a million at the start of the 20th Century, the Caspian seal has since undergone a dramatic decline of over 90 percent due to a range of human activities (1) (8) (9), and current losses still substantially exceed recruitment of young into the population (12). The species is particularly vulnerable as the Caspian Sea is a closed system from which the seal cannot disperse (1). The main threat to the Caspian seal is intensive commercial hunting (2) (3) (5) (9) (10), which, although now regulated, is still likely to exceed sustainable harvest levels (1). Illegal killing and poaching also occur (8). Intensive fishing is also a problem, reducing fish stocks and resulting in seals being caught as bycatch, injured by boats, or deliberately killed by fishermen (1) (2) (8) (9) (10). Fish stocks are also under further threat from the voracious comb jellyfish, Mnemiopsis leidyi, which invaded the Caspian Sea via ship ballast in 1999, and which rapidly consumes zooplankton as well as fish eggs and young (1) (9) (13).

The Caspian seal is also under serious threat from degradation of the Caspian Sea ecosystem. Pollutants such as DDT washing into the Sea from rivers have caused reproductive failure in female seals, as well as potentially weakening the seals’ immune systems, making the animals more vulnerable to diseases such as canine distemper virus (CDV) (1) (8) (9), which is believed to have caused the deaths of thousands of Caspian seals in 1997 and 2000 (1) (14) (15) (16) (17). Oil extraction and industrial waste are also problems (7), while oil field and coastal development are threatening shoreline habitats and causing disturbance at haul-out sites. Global warming may further reduce suitable habitat, by potentially causing a decline in ice cover (1) (9).

A range of measures have been put in place during the last century to protect the Caspian seal, such as a ban on seal nets and restrictions on hunting, including the protection of adult females during the breeding season (1) (11). However, legal hunting for commercial and scientific purposes still continues (1). A number of conservation projects are in place in the region, including the Caspian Environment Programme (CEP), which aims to halt environmental degradation in the Caspian Sea and promote sustainable development (4) (7), and the Caspian Seal Project, which is supported by bodies such as the UK Darwin Initiative, and which aims to monitor the Caspian seal population, work for its conservation, and raise its profile as a flagship species for the region. As part of this, a Seal Conservation Action and Management Plan (SCAMP) has been developed, although its most important recommendations have yet to be implemented (1) (9). The Caspian Seal Conservation Network (CSCN) is also coordinating research into the species (9).

Further conservation measures recommended for the Caspian seal include a ban on all hunting, measures to reduce bycatch, the creation of protected areas, and potentially, although controversially, introducing a predator to control the comb jellyfish (1) (9) (13). Present levels of Caspian seal mortality are not believed to be sustainable, and without urgent action it is unlikely that this unique mammal will survive in the long-term (1) (8) (9) (12).

To find out more about the Caspian seal, and about conservation in the Caspian Sea, see:

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  1. IUCN Red List (December, 2009)