Pusa sibirica 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Carnivora Phocidae

Scientific Name: Pusa sibirica (Gmelin, 1788)
Common Name(s):
English Baikal Seal
Taxonomic Notes: The Baikal Seal belongs to the Phocina group of northern seals, which includes the Ringed Seals (Pusa), the Harbour and Spotted Seals (Phoca), and the Grey Seal (Halichoerus). The radiation of the Phocina group is believed to have started in the northern seas of the late Pliocene, 2-3 million years ago, and was accompanied by invasion of the continental basins, though the paleogeography in this period is still not clear (Palo and Väinöla 2006, Fulton and Strobeck 2010).

The taxonomic relationships between the seals of the continental lakes and open ocean has long been debated, and the placement of the Baikal and Caspian Seals has varied between the genera Pusa and Phoca. Cladistic and phylogenetic studies from the 1970s to present, based on morphology, and more recently mitochondrial and nuclear gene DNA sequences datasets, considered Phoca, Pusa, Histriophoca, and Pagophilus to be a monophyletic group (Wozencraft 2005). These analyses support two clades, Pagophilus and Histriophoca and the Phocina group, Phoca, Pusa, and Halichoerus (Rice 1998, Bininda-Emonds et al. 2007, Arnason et al. 2006, Fulton and Strobeck 2010, Nyakatura and Bininda-Emonds 2012).

Using a multigene mitochondrial dataset, Palo and Väinöla (2006) considered Pusa not to be a monophyletic group, with the Phocina forming a polytomy. Arnason et al. (2006), using whole mitochondrial genome sequences concluded the Caspian Seal to be most closely related to the Grey Seal, with the Baikal Seal forming a sister taxon, with Phoca and Ringed Seals outside this group. Fulton and Strobeck (2010) using nearly 9,000 base pairs of nuclear gene sequences and complete mtDNA genomes, placed Halichoreus basal to the group, with Pusa and Phoca as sister clades. Pusa caspica was suggested as basal to the Pusa genus, with Baikal and Ringed Seals as sister taxa. The most recent assessment (Nyakatura and Bininda-Emonds 2012), a super tree analysis of all carnivora combining 114 trees from the literature and 45,000 base pairs of DNA sequence, supports the grouping of Halichoreus within Pusa, with Phoca as a sister clade. The Baikal Seal is indicated as basal to the grouping of Pusa caspica and Halichoreus grypus, with a divergence time of around 1.6-2 million years ago. Nyakatura and Bininda-Emonds (2012) advocate subsuming Halichoreus and Pusa within the Phoca genus.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2015-07-10
Assessor(s): Goodman, S.
Reviewer(s): Lowry, L.
Contributor(s): Dmitrieva, L. & Burkanov, V.
Facilitator/Compiler(s): Lowry, L., Ahonen, H., Pollock, C.M., Chiozza, F. & Battistoni, A.
The current population size of the Baikal Seal is thought to be at the level of the Lake Baikal ecosystem’s carrying capacity (80,000–100,000 individuals). If global warming continues the quality of habitat of the species will decline dramatically which may cause the population to decline. However, Baikal Seals have survived periods of quite extreme warming in the past and the population undergoes periodic monitoring such that declines would be detected rapidly should they occur. Thus, at the current time the Baikal Seal is listed as Least Concern.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Lake Baikal is located in southern Siberia, Russia, near the Mongolian border. The lake is 636 km long and at its maximum 79.5 km wide (Kutyrev et al. 2006). Baikal Seals are basically confined to Lake Baikal (31,570 km²), though they do travel short distances into rivers that flow into and out of the lake. An exception is one animal that was found 400 km downstream in the Angara River, the only river that flows out of the lake (Ivanov 1938, Pastukhov 1993, Rice 1998).
Countries occurrence:
Russian Federation
Additional data:
Estimated area of occupancy (AOO) - km2:34792Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:72677
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Following hunting in the early 20th Century, the Baikal Seal population increased from the 1970s through the early 1990s to over 100,000 individuals (Petrov et al. 1997; Petrov 2002, 2003). Population abundance subsequently declined slightly, probably due to commercial harvesting and outbreaks of canine distemper virus. Reports of current abundance vary between the different studies carried out since 2002, with estimates ranging between 82,500 and 115,000 individuals including pups (Petrov 2002, 2003, 2006; Ministry of Natural Resources 2013). The most recently reported figures derive from surveys carried out by the Russian Ministry of Natural Resources (2013), and report an increase from 97,400 individuals in 2012 to 108,200 in 2013, with an estimated pup production of 23,600, although the methodological details of this survey are not available. The population estimates may be subject to survey errors of about 30% (Petrov et al. 1997), and incomplete or inadequate coverage of the breeding range throughout the lake makes it difficult to draw robust conclusions about population demography. Therefore, short term abundance trends based on count data may merely reflect survey error variations. Currently Baikal Seals are considered to be at the carrying capacity level of the Baikal Lake ecosystem.
Current Population Trend:Stable
Additional data:
Number of mature individuals:54000Continuing decline of mature individuals:No
Extreme fluctuations:NoPopulation severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Baikal Seals are an exclusively freshwater species, and are thought to derive from the marine ancestor of the Pusa genus. It is hypothesized they colonized Lake Baikal from the Arctic via rivers and glacial dam lakes present in northern Siberia 300,000-400,000 years ago (McLaren 1960, Pastukhov 1969a, Koyama et al. 1997, Sasaki et al. 2003, Palo and Väinöla 2006). However, this is at odds with the current DNA sequence based estimate of around 2 million years for the divergence of the Pusa genus. This suggest a complex history of vicariance with the group, but the underlying paleogeography remains to be determined (Palo and Väinöla 2006, Fulton and Strobeck 2010, Nyakatura and Bininda-Emonds 2012).

Baikal Seals are among the smallest of the pinnipeds, with adults reaching 1.1-1.4 m and weights of 50-130 kg. Pups are born at 3-3.5 kg and approximately 70 cm (Pastukhov 1971, Thomas et al. 1982). Adult males at physical maturity are slightly larger than adult females of the same age. Final body size is reached at approximately 15 years of age (Amano et al. 2000). Males reach sexual maturity at 7-10 years of age (Pastukhov 1993). Female Baikal Seals become sexually mature between 3-7 years and some have their first pup by age 4, most by 5-6 years, with some not pupping until they are 9 years old (Pastukhov 1969b, Thomas et al. 1982). Baikal Seals continue to produce pups until they are 43-45 years old and may have the greatest longevity of any pinniped species. Approximately 10% of the population is older than 20 years of age, with records of adult females reaching 56 years of age and adult males 52 years of age (Pastukhov 1990, 1993).

The annual cycle of the Baikal Seal is driven by ice more than food (Ivanov 1938). In mid-October, the Seals begin to move towards bays, lagoons and river deltas, mostly along the eastern shore where ice forms and expands out into the lake. They spend January to May spread throughout the lake, usually singly, in deep water in the central basins. Adults stay primarily in the north while immature Seals are more often found in the southern part of Lake Baikal. Pups are born from late February to early April, with peak numbers born in mid March (Pastukhov 1990). Pupping takes place on the ice in dens that females actively build and maintain. During the pupping season, females are widely spread out on the ice. Their surface home ranges, including the den and breathing holes, are a minimum of 0.26 km² and do not overlap with other females (Ivanov 1938, Elagin et al. 1990, Pastukhov 1993, Martinkova et al. 2001). Pups do not usually enter the water for their first 2-3 weeks.

Most pups are weaned in 2-2.5 months, although some are believed to be nursed for 3-3.5 months (Pastukhov 1971). Females move pups and construct new dens if the dens become damaged; this may be necessary to protect small pups from predators. Mating is believed to take place in April, approximately one month after the female gives birth (Pastukhov 1993). Although births take place throughout the lake, more pups (51%) are born in the northern third of the lake, as compared to the central third (31%) or the southern third (17%) (Pastukhov 1971, Thomas et al. 1982, Petrov et al. 1997).

The ice breaks up in May and June, a time when Baikal Seals undergo their annual moult. More than half of the population moves to the remaining ice in the northern and northeastern parts of Lake Baikal, forming aggregations that can be as large as 1,000-3,000 animals. Moulting takes place during an approximately month-long period, during which Baikal Seals feed very little (Pastukhov 1993). Many Baikal Seals congregate in the southeastern part of the lake in the ice-free season to haul-out on rocky islands and shorelines between feeding excursions (Ivanov 1938, Pastukhov 1993, Petrov et al. 1997). The eastern side of the lake is preferred because it has less human disturbance and greater biological productivity (Pastukhov 1993). It is not known whether Baikal Seals have a regular annual movement pattern. Satellite-tagging of four juvenile Seals revealed that they moved throughout the lake in the course of a year, traveling from 400 to 1,600 km between September through May. Although it may not be typical of adult Seals, the pattern of frequent diving and movement demonstrates that juveniles move considerable distances and spend little time hauled-out during the fall and winter months. Two of the four Seals tagged in autumn returned to their tagging sites the following spring after wandering widely throughout the lake (Stewart et al. 1996). Diving patterns are not well documented; tagged juvenile Baikal Seals dived most frequently to between 10 and 50 m, with some dives exceeding 300 m. The mean depth in Lake Baikal is 758 m (Kutyrev et al. 2006). Dive depths were shallower at night, consistent with the vertical movements of their preferred prey fish, the two species of Golomyankas (Comeophorus spp.) that ascend from depths of 100 m or more during the day to forage at 10-25 m at night. Dive durations were generally 2-4 minutes, with 14-30% of dives lasting 6-10 minutes. The longest recorded dives exceeded 40 minutes and occurred during the winter in areas of heavy ice cover (Stewart et al. 1996). Baikal Seals feed on fish and 29 species have been recorded in their diet. Along with the two species of Golomyankas mentioned above, they also consume two species of Sculpin (Cottocomephorus spp.) as primary prey. Diversity of fish species consumed is highest in the summer with 17 species eaten, declining to 8 species in fall, and only 4 principal species eaten in winter. Juveniles may also consume amphipods during winter (Ivanov 1938, Pastukhov 1967, Gurova and Pastukhov 1974, Thomas et al. 1982).
Systems:Terrestrial; Freshwater
Generation Length (years):21.6
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: Subsistence hunting of the Baikal Seal extends back at least 9,000 years to the Neolithic period (Khlobystin 1963, Weber et al. 1993, Nomokonova et al. 2015). Commercial hunting began in the second half of the 18th century (Ivanov 1938, Pastukhov 1993), becoming a regular industry in the early in the 20th century. Annual harvests fluctuated between 2,000 and 9,000 Seals in the early 20th century, then from under 1,000 to nearly 6,500 in the 1930s (Svatosh 1923, 1925; Ivanov 1938). Harvests from 1977 to 1983 were consistently high. The official harvest quota and catch level was about 6,000, plus an estimated “unofficial hunting” level of up to 3,600 Seals (Pastukhov 1993). In the late 1980s and early 1990s the official statistics were not reliable and did not reflect the actual harvest level. Estimates vary between 4,000 and 8,000 animals (Petrov et al. 1997) killed annually. Harvesting continues today. During 2004-2006 about 2,000 Seals were reported killed in annual official statistics with estimations of an additional “uncounted” harvest of between 1,500 and 4,000 animals annually (Petrov 2007). The “uncounted” harvest includes wounded or drowned animals, incidental catch in fishing gear, and poaching. More recently, total hunting including poaching was estimated at between 2,300-2,800 annually for 2012 and 2013 (Ministry of Natural Resources 2013). A quota of 2,500 was set for the official hunt in 2013-2014, with a Potential Biological Removal level of 5,000 individuals. There are some calls to expand hunting, with skins, meat, and blubber as the products being utilized.

Threats [top]

Major Threat(s): Major rivers flowing into Lake Baikal pass through regions of industrial activity and there are concerns over contamination from persistent organic pollutants such as polycholorinated biphenyls (PCBs), dichlorodiphenyltricholoethanes (DDTs), dioxins, flame retardants and other related chemicals (Mamontov et al. 2000). Exposure to such bioaccumulative chemicals has potential to impair fertility and immunocompetence (De Swart et al. 1995, Kannan et al. 2000). Numerous studies have assessed contaminant levels in Baikal Seals from the 1990s to present (e.g., Kucklick et al. 1994; Nakata et al. 1995, 1997; Tarasova et al. 1997; Tanabe et al. 2003; Tsydenova et al. 2003, 2004; Iwata et al. 2004; Ishibashi et al. 2008; Imaeda et al. 2009). These show complex and varying temporal trends, with levels of DDTs and non-ortho PCBs declining through the 1990s to mid-2000s, while others such as mono-ortho PCBs showed no decline and perflourochemicals increased (Tanabe et al. 2003, Tsydenova et al. 2004, Ishibashi et al. 2008, Imaeda et al. 2009). This variation reflects differences in environmental half-life and rates of inflow of chemicals stemming from changes in industrial usage patterns.

Overall contaminant burdens at the population level for Baikal Seals are lower than pinniped species from areas of Europe and North America with high industrial contamination, but greater than Seals from ‘cleaner’ Arctic environments, although some individual animals have been found to have high burdens. The most recent study (Imaeda et al. 2009) found that 40% of Seals in the tested sample from 2005 had TEQ (Toxic Equivalent – a measure for summarising relative toxicity of complex contaminant mixtures) levels above a threshold associated with immune suppressive effects identified in Harbour Seals (De Swart et al. 1995). Organochlorine accumulation is age related, so older adult males are the most likely component of the population to be above these thresholds (Iwata et al. 2004). However, demonstrating effects of contaminants in the wild is difficult, and there is currently no direct evidence of contaminant burdens affecting disease susceptibility or influencing population demography in Baikal Seals. Recent studies on liver gene expression profiles in Baikal Seals suggest changes to liver metabolism consistent with toxicity in relation to environmental contaminant exposure, but the overall health significance is not clear (Hirakawa et al. 2011). Industrial development is increasing around the Baikal watershed so it is important that monitoring of contaminant exposure in Baikal Seals is continued in the future (Reijnders et al. 1993, Nakata et al. 1997, Mamontov et al. 2000, Grachev 2002, Imaeda et al. 2009).

An outbreak of a canine distemper virus killed approximately 6,500 Baikal Seals in 1987-1988 (Grachev et al. 1989, Pronin and Kabanov 1992, Belykov et al. 1997), and is believed to have been transmitted to Seals from a terrestrial source, probably feral or domestic Dogs (Barrett et al. 1992). Recent surveys show that the virus is still circulating in the population, although without causing further mass mortalities to date (Mamaev et al. 1996, Butina et al. 2003, 2010). However, future epizootics remain possible, and it is recommended that surveillance of CDV strains circulating in the population be continued (Butina et al. 2010). Natural predation does not appear to be a significant source of mortality for Baikal Seals, with only Brown Bears (Ursus arctos) reported as predators (Pastukhov 1993).

As a landlocked ice-breeding species, Baikal Seals may be vulnerable to future climate change since they cannot move to alternative habitats (Kovacs et al. 2012). Future climate warming has the potential to reduce the extent and duration of ice-habitat Baikal Seals rely on for breeding, and to also affect Baikal food webs (Mackay et al. 2006, Hampton et al. 2008, Moore et al. 2009), both of which could drive population declines. The potential effects of changes in winter ice on Baikal Seal population demography remain to be assessed in detail, but the species has persisted through previous episodes of climate variation.

Conservation Actions [top]

Conservation Actions: Numerous measures, such as establishing commercial harvest quotas, changing methods and equipment used for harvesting Seals, and changing the timing of the hunt and the age class of Seal that can be taken, have all been used during the history of the commercial harvest to regulate the catch (Svatosh 1923, 1925; Ivanov 1938; Pastukhov 1993; Petrov et al. 1997). Recent recommendations for the protection and conservation of the Baikal Seal include several measures to reduce the impact of poaching by local residents (including increased penalties for illegal hunting) and mandatory reporting of incidental catch in fishing gear (Pastukhov 1993). There are many protected areas and reserves throughout Lake Baikal.

Citation: Goodman, S. 2016. Pusa sibirica. The IUCN Red List of Threatened Species 2016: e.T41676A45231738. . Downloaded on 24 September 2018.
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