Caspian Seal

## About

A Caspian seal.

The Caspian seal ***(Pusa caspica)*** is a true seal and the only mammal native to the Caspian Sea. Adult Caspian seals differ in appearance to juveniles. While seal pups have white or silver fur (known as lanugo), whereas adult will have silver or grey coloured bodies, with lighter white or yellow underbellies. Males are typically darker in appearance compared to females. Caspian seals also have mottled or blotched patterning across their bodies that varies between individuals and is darker than their main coat. Like all true seals, the Caspian seal has a stoat body with hind flippers that out stretch backwards from the main body. This body plan makes the Caspian seal much less dexterous on land than earless seals, similarly to other true seals. Because of this, Caspian seals move on land through means of dragging themselves forward with their front flippers, or bouncing in a caterpillar-like motion. The Caspian seal is one of the smallest seals. It can grow to a length of 0.9-1.5m (3-5ft) and weighs 31-49kg (10-110lbs).

## Diet

The Caspian seal's diet varies around the time of year and water depth. Typically sprats ***(Cluponella)*** make up 70% of the Caspian seal's diet and sculpins, carp, gobies, herring, crustaceans and smelt.

## Conservation Status

Caspian seals are classified as endangered by the IUCN. The reason for the Caspian seal's steep decline in population can be mostly attributed to the mass hunting that occurred during the 20th century, that has continued into the modern day. Juvenile seal mortality is believed to be unsustainable and is caused by the combined efforts of bycatch, predation, and continued hunting. A continued rate of juvenile mortality could very well continue the Caspian seal's current decline. Illegal sturgeon fisheries which supply the caviar trade often cause seal casualties in the form of bycatch. Caspian seals become ensnared in bycatch and typically die. In the Dagestan and Astrakhan regions of Russia and the Atyrau region of Kazakhstan, a minimum bycatch rate of 1,215 seals in 2008-2009 was recorded, 93% of which were caused by sturgeon fisheries. Unfortunately, this study reflected only 10% of all poaching occurring in the Northern Caspian Sea. This means that the actual bycatch level is substantially higher and likely succeeds the species' Biological Removal Level. Along with this, the study also did not record bycatch levels in the Central and Southern regions of the Caspian Sea. It is believed that Iranian fisheries -the highest producers of sturgeon caviar worldwide- cause a seal mortality rate of 500 Caspian seals annually. Fishermen in the area have also been known to often sell seal products from bycaught seals, such as skin and blubber. Canine Distemper Virus (CDV), can be attributed to the mass casualties of Caspian seals caused in the years of 1997 and 2000-2001, the disease killed several thousand seals on each occasion. This disease was recognised in Caspian seals when a deceased individual was found to be carrying CDV in 1997. It was likely the same strand of CDV that caused the mass casualties that occurred in the following years of 2000-2001 in Azerbaijan and Kazakhstan. Later, the examination of archival records in Azerbaijan dated back to 1971, suggested that CDV has outbroke many times in the past and it has an increasing mortality rate. Luckily, no large mass casualties have occurred since the 2001. Organochlorine levels, particularly polycholorinated biphenyls (PCBs) and dichlorodiphenyltricholoethanes (DDTs) were assessed surrounding the mass casualties. Most Caspian seals were found to have levels below the particular threshold for intoxication in most mammalian species. Comparatively to European seal species, Caspian seals had far lower levels and far higher levels compared to Arctic seal species. The Caspian seal could be likened in level to another Asian seal species, the Baikal seal ***(Pusa sibirica)***. There is currently no evidence supporting the fact that organochlorine burdens are apparent in Caspian seals that inhibit the reproductive or immune systems in the seals, with the exception of very few individuals. Despite this, there is evidence that supports the fact that organochlorine burdens exist in older individuals, as their thresh-holds may be reduced with age. Because of this evidence, it is suggested that organic pollutants in the Caspian Sea be monitored, due to the continued industrialisation in the region. Comb jellies were introduced to the Caspian sea via the ballast water from ships in the Volga-Don canal during 1991. As comb jellies ***(Mnemiopsis leidyi)*** rapidly consume zooplankton, fish populations fall, greatly inhibiting the Caspian seal's survival. Comb jellies have also caused many fisheries to go out of business, specifically in the Southern Caspian Sea. As the Caspian Sea is an inland lake and not truly a sea, there are no present outlets. Water is obtained from the Ural and Volga-Don canals. Unfortunately, the Volga-Don specifically has become rather polluted since the 1980's, harbouring metals such as; zinc, copper, cadmium and lead. Luckily for the Caspian seals, this does not seem to have impacted them largely, with the exception of zinc found apparent in the bodies of a few deceased individuals. Due to the Caspian seal's landlocked range and breeding habits, the species is incredibly vulnerable to climate change, as it has no alternative habitat to move to. As Caspian seals are an ice-breeding species, the ice sheets breaking before seal pups molt could prove catastrophic for the seal's population. For example, in January-March of 2007, the ice sheets were reduced and narrow, only occurring in the Northeast Caspian sea. Climate fluctuations in mid-February have caused thunderstorms to sweep ice sheets of pups away from the Caspian coastline. The decrease in breeding range has caused individuals to become enclosed in small areas, increasing the possibility of continued CDV outbreaks. The coastline of the Caspian sea is also being further industrialised, with the countries of Azerbaijan, Iran and Kazakhstan increasing public leisure use of the Caspian sea in recent years. Oil drilling is very apparent in the Caspian Sea and currently, one of the world's largest oil fields is being constructed in the Caspian sea. Unfortunately, studies show that Caspian seals are using the recently built shipping canals associated with oil drilling operations in order to access their breeding range. This has proven dangerous, as female seals are more likely to give birth to their pups on the shores of these canals, which can lead to disturbances or even mortality. Illegal fishing activity continues to disturb Island and reef haul-out sites, which are essential to the Caspian seal's long term survival.From the combined efforts of illegal hunting and haul-out site disturbance, the Caspian seal has effectively disappeared from its Azerbaijani range in the Caspian Sea, with only a few live individuals being found in the country's Caspian range since 2004. This disappearance was most likely caused by continued disturbances on the Apsheron peninsular and Archipelago haul-out sites. Caspian seals gathered in the thousands at these essential sites until the 1930's, when seal clubbing was prolific in the region. Ashoora Island in Iran has also been abandoned by seals and the Ogurchinsky Island population in Turkmenistan has been reduced to a mere couple hundred. Areas in Kazakhstan such as South West and Osushnoy Island as well as Bautino are also beginning to loose their seal populations. Through these combined threats, the Caspian seal's population is believed to be decreasing by 3-4% annually. Intervention is desperately required for the species.

## Range and Population

Caspian seals are the only mammals endemic to the Caspian sea and inhabit almost every area in the lake, with the exception of coastal Azerbaijan. Caspian seals inhabit every environment in the Caspian, ranging from the warmer Southern waters in Iran and Turkmenistan on sunny coastlines, to the northern waters in Russia and Kazakhstan where vast ice sheets form. Rarely, the Caspian seal may swim up rivers and canals, into the open ocean. Unlike Arctic seal species, the Caspian seal does not dive deeper than 10-200m (32-656ft). Though the current population of the Caspian seal is around 104,000-168,000 individuals, with only 68,000 being sexually mature, the historic populations ranged into the millions however, due to pressures discussed in-depthly above, the species' population has continued to decrease.

## Behaviour

Caspian seals have been recorded diving longer and deeper than their recorded thresh-holds. They rest at the waters surface when not hunting. The general behavioural characteristics of the Caspian seal are presently understudied and unclear. During the late Autumn months, seals will migrate to the northern Caspian Sea in order to rear their young. Females will give birth to their pups on the frozen ice sheets of the northern Caspian Sea after a gestation period of 11 months. A delay in the implantation of the egg may be apparent due to the species' long gestation however, this idea is not supported by scientific evidence. Pregnancy rates are at an all time low of 30% due to threats and conservation issues. Females only birth one pup, which will reach sexual maturity at 6-7 years if male and 5-7 years if female. Breeding reoccurs in February to March, after the weaning of the first pup however, it may occur while the pup is still nursing. Following late April, the north begins to warm and ice sheets melt. Caspian seals will then migrate back to the cooler and deeper waters of the south to enjoy the Summer months. Caspian seal pups cannot enter the water until molting an adult coat, as swimming may render them cold and susceptible to freezing.

### Relationship with Humans

Caspian seals are friendly towards humans. They will often interact with people or jump onto fishermen's boats. Caspian seals have also been known to follow fishing boats in order to play with the fishermen's catch.

## Sources

* IUCN Red List of Threatened Species - https://www.iucnredlist.org/species/41669/45230700
* Caspian Seal | Animal Diversity Web, University of Michigan Museum of Zoology - https://animaldiversity.org/accounts/Pusa\_caspica/
* Caspian Seal | Oceans of Fun - https://www.oceansoffun.org/pinniped\_species/31
* Caspian Seal: Why is it Endangered? | Our Endangered World - https://www.ourendangeredworld.com/species/caspian-seal/