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Pusa caspica

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA PHOCIDAE

Scientific Name: Pusa caspica
Species Authority: (Gmelin, 1788)
Common Name/s:
English Caspian Seal
Synonym/s:
Phoca caspica Gmelin, 1788
Taxonomic Notes: The Caspian Seal belongs to the Phocina group of northern seals, which includes the ringed seals (Pusa), the harbour and largha seals (Phoca) and the grey seal (Halichoerus). The radiation of the Phocina group is now believed to have started in the northern seas of the late Pliocene, 2-3 MY ago, and was accompanied by invasion of the continental basins, though the paleogeography in this period is not clear (Palo and Väinöla).

The taxonomic relationships between the seals of the continental lakes and those of the open ocean remain unclear, and the placement of the Caspian Seal has varied between the genera Pusa (Gmelin 1788) and Phoca. Following Wozencraft (2005): "Burns and Fay (1970), Rice (1977), McDermid and Bonner (1975), Gromov and Baranova (1981), King (1983), and Wyss (1988) considered Phoca, Pusa, Histriophoca, and Pagophilus a monophyletic group. Cladistic analysis based on morphology and mtDNA revealed two clades, Pagophilus+Histriophoca and the Phocina group, Phoca+Pusa+Halichoerus (Muizon 1982, Mouchaty et al. 1995, Perry et al. 1995, Carr and Perry 1997, Rice 1998, Bininda-Emonds et al. 2007). In the most recent phylogenetic studies using large mtDNA datasets, Palo and Väinöla (2006) consider Pusa to be basal to the Phocina, but suggest that the Caspian Seal is most closely related to Phoca and Halichoerus, while Arnason et al. (2006) suggest the Caspian Seal to be most closely related to the Gray Seal, with the Baikal Seal forming a sister taxon, and Phoca, Ringed Seals being basal to this group.

Assessment Information [top]

Red List Category & Criteria: Endangered A2abd+3bd+4abd ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor/s: Härkönen, T. (IUCN SSC Pinniped Specialist Group)
Reviewer/s: Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
Due to a decline exceeding 50% over the last three generations, reduction in the number of sites used (range reduction within the overall geographic range), current hunting levels that almost certainly exceed sustainable harvest levels and the multiple ongoing negative impacts on the habitat of the Caspian Seal, this species should be classified as Endangered (EN).

IUCN Evaluation of the Caspian Seal, Phoca caspica
Prepared by the Pinniped Specialist Group


A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.

Modelling based on hunting statistics and surveys (2005-2007) suggests a population decline exceeding 70% over the past three generations. Age-structure data are not directly available for the Caspian seal population, but the maximum longevity is about 50 years. Generation time was inferred by modeling at 16.3 years when measured as the mean age of females giving birth to a cohort, and at 17.1-18.0 when measured as time for increase of R0. Three generations would then be 49-54 years. The minimum number of reproducing females in 1955 was estimated to be 117,000. Current pup production was estimated to be 20,000 in 2005, 16,500 in 2006, and 5,700 in 2007. The decline in the size of the adult female reproducing population over the past three generations is therefore inferred to be in the range in excess of 70%. Current hunting quotas exceed the annual pup production in many years, seal mortality in fishing operations is commonplace, CDV has caused mass mortality, and Caspian Seals are suggested to have impaired reproduction as a consequence of environmental pollution. This species meets the criterion for Endangered, except that the decline has not ceased.

A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

The inferred and observed decline may not have ceased. Pup production is thought to be in sharp decline.

A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.

A further population reduction of Caspian Seals is suspected in the future because of predicted reduction in sea ice habitats due to continued climate warming, hunting, by-catch in fisheries, disease and pollution. The likely amount of population reduction has not been projected, but could exceed 50% within the next 30 years. This meets the criterion for classification as Endangered.

A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under Al.

A population reduction of Caspian Seals exceeding 50% has been observed, estimated and inferred, over the past 30 years, and causes for this reduction have not ceased. This meets the criterion for Endangered.

B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²

The EOO of Caspian Seals is > 20,000 km².

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

The AOO of Caspian Seals is > 2,000 km².

AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

The current abundance of Caspian Seals is certainly > 10,000, but the number of reproducing females has fallen to less than 10,000.

AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
or
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

The number of mature individuals is certainly > 1,000. AOO is > 20 km² and the number of locations is > 5.

E. Quantitative analysis
Indicating the probability of extinction in the wild to be: Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years

There has been no quantitative analysis of the probability of extinction for Caspian Seals.

Listing recommendationPopulation size exceeded one million in the 1930s, when more than 100,000 seals (of all age classes) were killed annually. Numbers of reproducing females have decreased from about 117,000 to between 20,000 and 8,000 over the past three generations, which indicates a decline of more than 70%. Recent surveys suggest that this decline has not ceased, but is ongoing. The distribution of the Caspian Seal in a completely closed ecosystem, from which individuals cannot disperse, makes it vulnerable to some or all of the many threats it currently faces. Major pan-Caspian changes such as reduction in stocks of prey fish (due to over-fishing and the jelly-fish Mnemiopsis) and reduction in the seal’s breeding habitat (i.e., ice reductions due to climate change and possibly oil extraction operations) and loss/degradation of other habitat features threaten the species’ viability. Current and future large-scale mortalities due to hunting, fisheries operations and disease (such as CDV) will likely continue to drive the current population decline. Caspian Seals qualify for listing as Endangered under IUCN criteria A2abd+3bd+4abd.
History:
1996 Vulnerable
1996 Vulnerable
1994 Vulnerable (Groombridge 1994)

Geographic Range [top]

Range Description: Caspian seals are confined to the Caspian Sea. They range throughout the sea with seasonal migration between the southern, middle and northern basins. Almost all breeding takes place on ice, which covers the shallow northern parts of the Caspian Sea in winter. Occasional observations of low numbers (tens) have been made at islets off Turkmenistan.
Countries:
Native:
Azerbaijan; Iran, Islamic Republic of; Kazakhstan; Russian Federation; Turkmenistan
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Historically, the population of Caspian seals was estimated to have exceeded one million (Krylov 1990, Härkönen et al. 2005). However, the most recent abundance estimate of the total population is in the region of 111,000 in 2005. This estimate was based on an estimate of pup production that year of about 21,000 pups (95% confidence intervals 19 329 to 22 797), derived from counts made during aerial transects across the winter ice conducted in late February 2005 (Härkönen et al. 2005, 2008).

The population decline throughout the 20th century has been reconstructed by a demographic model using hunting statistics (Härkönen et al. 2005). By the 1950s–1960s, the population was estimated from this model to have been reduced to between 400,000-500,000 seals (Härkönen et al. 2005), while an estimate based on a harvest of 86,000 pups in 1966, believed to be most pups born that year, also produced an estimate of 500,000 seals for that year (Badamsin 1969, cited by Krylov 1990). Aerial surveys conducted in 1976 and 1980 suggested an estimate of 450 000 animals (Krylov 1984, cited by Krylov 1990), although the hind-casting analysis suggests a population of only about 200,000 seals remaining at that time (Härkönen et al. 2005). Surveys in 1987 and 1989 resulted in an estimate of approximately 360,000-400,000 (Krylov 1990), but again the hind-casting analysis suggests this might again have been an over-estimate, with perhaps only about 148,000 seals remaining by the late 1980s. The hind-casting analysis suggests an ongoing population reduction averaging about 3-4% per year since 1960 and an 83% reduction in the size of the breeding female population since 1955 (approximately 3 generations, with one generation being 16.5-20 years , Härkönen et al. 2005).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: During late spring, summer, and early autumn, Caspian seals are distributed throughout the Caspian Sea. They feed throughout the sea, exploiting both the shallow basin in the north and the deep middle and southern basins. After the ice melts, the seals use sandy islands and reefs as haulout sites, preferring the tips of peninsulas and sand bars in many areas, although large concentrations of seals in reed-bed areas of islands also occur. In late autumn the breeding adults gather in the northeast, hauling out on sandy islands and reefs in increasing numbers until sea ice begins to form (Krylov 1990). When the surface freezes over, females form aggregations on the ice to give birth to their pups, tending to gather along cracks in the ice giving them ready access to the water, although they also construct and maintain holes in the ice for water access (Heptner 1996, Härkönen et al. 2008).

Pups are generally born from mid-January to late February on the ice and nursed for 4-5 weeks. Females do not usually construct lairs (Frost and Lowry 1981), possibly because sufficient amounts of snow overlying the ice is normally lacking. Pupping on the ice has allowed direct counts of pups to be made in the recent aerial surveys (Härkönen et al. 2008). Pups do not enter the water until the ice melts in mid to late March.

The first documented observations of small numbers of seals breeding in other parts of the Caspian were made in 1982, with females reported pupping on small sand islands in the southern part of the Caspian Sea, although it is likely this behaviour was not new (Krylov 1990).

Large numbers of mostly nonbreeding seals spend the winter in the middle and southern Caspian, with one estimate of 15,000 seals along the Turkmenistan coast (Krylov 1990). A post-breeding moult occurs from April to May, during which the seals first use the ice and then islands and reefs for hauling out (Krylov 1990).

Both sexes become sexually mature at around 6 years of age, with most breeding females (74% in a 1974 sample) aged between 8 and 17 years (Popov 1982). The pregnancy rate for females older than 9 is reported to be as low as 0.2-0.33 (Watanabe et al. 1999, Miyazaki 2002), and Krylov (1990) reports a similar low rate of 0.34 for females aged 10-14 years. Härkönen et al. (2005), acknowledge that the reproductive rate is low in females >20 years old, but suggest that the reproductive rate is >0.5 for females et al. (1999) and Härkönen et al. (2005) attribute the lower reproductive rates of older females to the effect of long term exposure to organochlorine contaminants in the older animals.

Caspian seals feed on a variety of fish species. During the summer and autumn, seals move to and congregate where prey are abundant, particularly Caspian kilka (Clupeonella sp.), Caspian silverside (Atherina mochon), and Caspian gobies (Gobidae) (Krylov 1990), with Clupeonella species historically making up a major proportion of their total annual diet (Kosarev and Yablonskaya 1994). A report on fish found in the stomachs of seals in the northern Caspian in 1986-1987 (Piletskii and Krylov 1990) suggested that fish eaten in order of frequency were roach (Rutilus rutilus), zander (Lucioperca lucioperca), gobies (Knipowitschia sp., Neogobius kessleri and Benthophilus sp.), and bream Blicca bjoerkna and Abramis brama), followed by Clupeonella deliculata and other species. A preliminary study from faecal samples on the Apsheron Peninsula in June 2001 and March 2002 suggested that gobies, silverside and shrimp were important constituents of the diet of seals hauled out at that time (Eybatov et al. 2002). New studies of diet in Caspian seals are urgently required in order to get an accurate picture of current prey in different areas of the Caspian in light of potential changes to the abundance of fish species due to recent ecological changes occurring in the Caspian Sea.
Systems: Terrestrial; Freshwater

Threats [top]

Major Threat(s): Caspian seals have been commercially exploited on an intensive basis since the early 1800s. Harvests averaged 119,000-174,000 per year throughout the 19th century, with peaks of 300,000 having been recorded. In the 20th century, harvest levels peaked in the 1930s with an average annual harvest of 164,000 and a maximum single year take of 227,600. The numbers of seals taken fell during World War II to an average of 60,800 per year, and subsequently ranged between a low of 41,400 and a high of 108,300 for the period 1951-1975 (Krylov 1990). Commercial harvesting was temporarily halted in 1996 after a much-reduced estimated take of 14,000 seals. Commercial and scientific hunting in the region of 3,000-4,000 seals a year – mainly pups - has continued at least since 2004, and is currently ongoing. The hunting quota, set by the Caspian Bioresources Commission for 2007, was 18,000 seals which exceeded the estimated annual pup production for that year (Harkonen et al. 2008).

Significant population declines have been attributed to the high harvest levels (Härkönen et al. 2005). Another contributory cause to high pup mortality is natural predation by wolves (Canis lupus) and sea eagles (Haliaeetus spp.). Krylov (1990) estimated that wolves killed 17-40% of Caspian seal pups on “some breeding grounds from 1974 to 1976”, while eagles took less than 1% of pups. The reverse was found during a systematic survey by Harkonen et al. (2008). Few wolves were observed during this survey, but about 2,000 eagles were seen on the ice preying on pups in 2005-2006; they likely took approximately 10% of the annual estimated births of 20 000 pups.

By-catch of seals in fisheries and killing of seals by fishermen are threats that have not been adequately investigated, but are thought to be a significant source of mortality, particularly for juvenile seals (Härkönen et al. 2005). The Iranian commercial fishery is of conservation concern; it is likely responsible for the deaths of an estimated 500 seals annually (Eybatov et al. 2002). But, by-catch in legal and illegal fishing activity in the northern Caspian is likely to exceed this number substantially. This by-catch may amount to several thousand animals per year, with local fishermen in the Mangistau region of Kazakhstan citing catches exceeding 200 seals per 5 km of nets set (Goodman, Wilson and Dmitrieva unpublished data based on interviews November 2007).

Mass mortality events in 1997 and 2000-01, killing several thousand seals each time, have been attributed to a morbillivirus, canine distemper virus (CDV). Presence of a hitherto unknown strain of this virus was confirmed in one dead seal in 1997 (Forsyth et al. 1998), and the same strain was confirmed as the primary cause of death in seals dying in 2000 in Kazakhstan and Azerbaijan (Kennedy 2000, Kuiken 2006). The cause of a further mass mortality in 2001 was less clear (Eybatov et al. 2002). Examination of archive stranding records in Azerbaijan since 1971, show an increased mortality every few years, suggesting the possibility of previous outbreaks of CDV. A serology study of archived samples indicated that CDV was present in Caspian seals in 1993, 1997 and 1998 (Ohashi et al. 2001).

Degradation of the Caspian Sea ecosystem and overexploitation of primary food resources are also threats to Caspian seals (Reijnders 1993). An invasive of comb jellyfish, Mnemiopsis leidyi, arrived in the Caspian Sea via ship ballast water in the Volga-Don Canal in1999 (Ivanov et al. 1999). Mnemiopsis consumes zooplankton rapidly, leading indirectly to a reduction in fish stocks and a substantial impact on local fisheries. A 70% reduction in commercial landings of three species of Kilka (Clupeonella spp.) was recorded within 3 years of the comb jellyfish invasion (Kideys et al. 2005). Kilka are thought to be important prey for Caspian seals in the central and southern parts of the sea, and the invasion of Mnemiopsis is considered a threat to the seals (Ivanov 1999, Eybatov et al. 2002).

The Caspian Sea has no outlet and receives most of its input from the Volga, Ural and other rivers. Contamination of the Volga with lead, copper, zinc, and cadmium has increased dramatically since the mid-1980s, but levels in seals appear not be elevated, with the exception of zinc in some diseased animals, which may have suffered homeostatic disturbance of trace metal levels (Anan et al. 2002). Organochlorine levels in Caspian seals dying in the 2000-01 epizootic were high when compared to other marine mammal species suffering from epizootic disease outbreaks. The most significant organochlorine contaminant in Caspian seals was found to be DDT (Hall et al. 1998, Kajiwara et al. 2002). Environmental contaminants, particularly organochlorines, may affect the overall Caspian seal population health by causing decreased reproductive rates, particularly in older females (Krylov 1990, Eybatov et al. 2002, Härkönen et al. 2005). Decreased immune function has also been suggested as a contributory cause of the CDV epizootic in 2000 (Kajiwara et al. 2002), and the deaths in 2001, although scrutiny of organochlorine levels in seals dying in this outbreak did not provide supporting evidence for this (Kuiken et al. 2006, Eybatov et al. 2002).

Total juvenile mortality from continued hunting, natural predation and fisheries by-catch is believed to be unsustainable. Overall mortality in the first year of life from all sources is likely to be in the region of 50% (Härkönen et al. 2008). The high rate of juvenile mortality has been singled out as the primary reason for the continuing decline in the Caspian seal, with lowered fertility due to organochlorine contamination being a relatively minor factor (Härkönen et al. 2005).

It seems likely that warmer winters occurring in the near future may contribute to the further decline of Caspian seals if there is reduced ice cover in the northern Caspian. In 2007 the ice cover was limited to a narrow strip along the coastline of the north-east Caspian, and breeding was therefore concentrated along this strip of ice. The number of pups alive at the end of February, estimated from the aerial survey, was fewer than 7,000, i.e. fewer by half compared to the number counted in the previous two years (Härkönen et al. 2008). It has also been suggested that poor ice conditions may play a role in the epidemiology of CDV outbreaks due to seal crowding on limited haulout space and poor condition of weaned pups (Kuiken et al. 2006). However, there is no evidence for this at present.

Further threats to the seals on shore and on ice now come from increasing disturbance due to offshore and shoreline developments. One of the largest oil fields in the world is currently being developed in the Caspian, with the construction of numerous offshore oil drilling islands, pipelines, shipping access to these, and onshore logistics facilities. A recent study found that breeding seals are using shipping channels as artificial leads into the ice and are giving birth close to the edge of these channels. A significant proportion of the breeding population and pups may therefore experience disturbance by shipping traffic depending on the ice conditions (Härkönen et al. 2008). More research is required to quantify the likely impacts of this intensive oil development. The coasts of Azerbaijan and Iran have also seen increased development for domestic and leisure use in recent years, with many previously undisturbed stretches of coast now being developed.

Disturbance of island and reef haulout sites by illegal fishing activities and opportunistic seal hunting are another ongoing problem. Recent surveys have found that the Caspian seal has effectively disappeared from Azerbaijan, with the once important haulout sites of the Apsheron Peninsula and Archipelago abandoned. These sites were used by many thousands of seals until the 1930s, when they were heavily hunted (Krylov 1990). However, between 1997 and 2002 a few hundred seals were still counted regularly at these sites (e.g. Allchin et al.1997, S. Wilson, unpublished observations). Few live seals have been seen in this area since 2004 (T. Eybatov, S. Goodman, S. Wilson, unpublished observations). The overall Caspian seal population decline between 2002 and 2004 is unlikely to account for this total disappearance, which is most probably due in part to severe disturbance by illegal fishing and other coastal activities (T. Eybatov unpublished data). Similar declines in the regularity of seal occupancy have also been noted recently at other sites, such as South West Island near the Ural Delta and Osushnoy Island (Kazakhstan) and in Turkmenbashi Bay (Turkmenistan). The number of seals at Ogurchinsky Island (Turkmenistan) has also declined from several thousand in the 1980s to a few hundred (P. Erokhin, unpublished observations). The only previously recorded haulout site in Iran, at Ashoora Island, is no longer used by seals (H. Asadi, pers. com.). There is an urgent need to develop an inventory of all haulout sites throughout the Caspian together with archived and current records of seal occupancy.

Conservation Actions [top]

Conservation Actions: Various prohibitions, quotas and protective measures have been taken to conserve the Caspian seal beginning in 1940 when seal nets were prohibited. The harvest of moulting seals in the spring was ended in 1946, and in 1952 the Apsheron Archipelago off Azerbaijan was closed to sealing. Female harvesting on the breeding grounds was stopped in 1966 and all take was prohibited on the “eastern islands of the northern Caspian in 1967.” These last two changes led to a complete change in the commercial harvest in 1966 resulting in a switch to newborn and moulted pups. Quotas on harvest of pups, supposedly based on biological data, began in 1970 (Krylov 1990), although clearly these quotas were unsustainable. The Russian Federation continues to consider the Caspian seal to be a ‘harvested’ species and unsustainable quotas are continuing to be set through the Caspian Bioresources Commission (Härkönen et al. 2008), e.g. 18,000 pups in 2007.

A Seal Conservation Action and Management plan has been approved by the nations bordering the Caspian Sea, pursuant to the 2003 Framework Convention for the Protection of the Marine Environment of the Caspian Sea (see Harkonen et al. 2005; Caspian Environment Programme 2007), but this has as yet no legally binding action points. The cessation of all types of hunting, measures to reduce by-catch in legal and illegal fisheries, and the strategic creation of protected areas of sea, ice and shore would appear to be the only way forward in the conservation of this species.
Citation: Härkönen, T. (IUCN SSC Pinniped Specialist Group) 2008. Pusa caspica. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 17 April 2014.
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