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Saimaa ringed seal

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Saimaa ringed seal
Saimaa ringed seal pictured in 2023
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Pusa
Species:
P. hispida
Subspecies:
P. h. saimensis
Trinomial name
Pusa hispida saimensis
(Nordquist, 1899)
Synonyms
Phoca hispida saimensis

The Saimaa ringed seal (Pusa hispida saimensis, Finnish: saimaannorppa) is a subspecies and glacial relict of ringed seal (Pusa hispida).[2] They are among the most endangered seals in the world, having a total population of only about 400 individuals.[3] The only existing population of these seals is found in Lake Saimaa, Finland (hence the name). They have lived in complete isolation from other ringed seal species for around 9,500 years and have diverged into a morphologically and ecologically different subspecies of ringed seal.[4] The population is descended from ringed seals that were separated from the rest when the land rose after the last ice age. This seal, along with the Ladoga seal and the Baikal seal, is one of the few living freshwater seals.

Distribution

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Habitat

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The Saimaa ringed seal is endemic to their habitat in Lake Saimaa, Finland. The lake lies between the cities of Lappeenranta in the south and Joensuu in the north, spanning an oval of approximately 180 by 140 km (112 by 87 mi). It consists of numerous larger basins connected by narrower glacier-carved channels, and its geography is maze-like, having 13,710 islands, an approximate coastline length of 14,850 kilometres (9,230 mi), and a surface area of 4,279 km2 (1,652 sq mi).[5] It is relatively shallow, having an average depth of 17 metres (56 ft)[6] and a maximum depth of 85.8 m (281 ft).[5] The freshwater lake freezes over between the months of November and May, leaving the seals both an ice habitat and an open water habitat.[7] During summer months when the ice is melted, these islands provide ample space for the seals to molt and breed.

Range

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Saimaa ringed seals are named as such due to their only habitat being Lake Saimaa, Finland. Thus, their range is restricted only to the waters of Lake Saimaa and its surrounding banks.

Appearance

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A stuffed Saimaa ringed seal at the Finnish Museum of Natural History.

An adult Saimaa ringed seal is between 85 and 160 centimetres (2.79 and 5.25 ft) in length and weighs between 50 and 90 kilograms (110 and 200 lb); males usually being larger than females. They are coloured dark gray, with a gray-black dorsal with circular white rings. The bottom of the seal is light gray. The Saimaa ringed seal is darker in color than any other ringed seal.

Diet

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The Saimaa ringed seal does not have an incredibly varied diet. They are generalist feeders and eat exclusively fish.[8] The fish consumed consist primarily of small schooling fish averaging 8.6 cm in length and up to 21 cm in length,[8] while it has been shown that the pups eat slightly smaller fish than the average.[8] The majority of their diet consists of vendace, smelt, perch, and roach.[9] The pups’ diet varies markedly from the adults in that their diet consists primarily of perch and roach found in the shallow water[10] where they spend most of their time in their earlier months, while the adults consume more vendace and smelt.

It was believed for a long time that the Saimaa ringed seal was competing with the commercial and recreational fishing industries and there were bounties paid on them until the 1940s.[8] However it has recently been proven that the Saimaa ringed seal has minimal to no effect on the fishing industry. They do not prey on the local endangered salmon species (Salmo salar m. Sebago, S. trutta m. lacustris, and Salvelinus alpines).[8] Although they do prey on the valuable vendace population, the proportion of the vendace population to the amount consumed by the seals indicates that they do not compete with the local fishing industries.[8]

Behavior

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Reproduction

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Saimaa ringed seals become mature between the ages of 4 and 6. Their pregnancy rate is between 80 and 95 percent. Ringed seals' gestation lasts 11 months. Their pups are between 55 and 65 centimetres (1.80 and 2.13 ft), and 4 to 5 kilograms (8.8 to 11.0 lb) at birth. The Saimaa ringed seal's longevity is just over 20 years.

A study conducted from 1980–84 revealed that Saimaa ringed seals make burrowed dens close to the shore and they reproduce once a year due to their longevity.[11]

Saimaa ringed seals have two kinds of lairs or dens; they have a haul out lair where no breeding takes place, and the breeding lair. Breeding lairs are located closer to the shore than haul out dens.[12]

Diving

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Diving is an important behavior for aquatic mammals as it is something they rely on for behaviors such as foraging and travelling. The duration of their dives increases from spring to autumn, which may be a result of food availability, but it is interesting because they are one of the few landlocked seal species.[13] Many studies have been done to observe Saimaa ringed seal diving, which was discovered to last longer than expected. Their average time for a long dive was recorded at 15 minutes and it was believed to be an aerobic resting dive.[7]

The average dive depth ranges from 10 to 15 m; however, their maximum dive depths were limited by environmental depth.[7] The Saimaa ringed seal has also been observed to have seasonal hauling-out patterns. In May and June, when the seals are molting, they are observed to haul out both day and night; however, in late summer they are observed to haul out only at night.[13]

The Saimaa ringed seal is able to complete its dives and navigate in its environment due to its highly developed vibrissae, also known as whiskers. Using their vibrissae, they are able to detect sound and pressure waves in their otherwise dark environment.[14]

Conservation

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1986 Finnish commemorative stamp designed by Pirkko Vahtero to the issue "EUROPA 1986 - Nature Conservation"; drawing with a Saimaa ringed seal in binocular view

The Saimaa ringed seal has been protected by law in Finland since 1955; it is also listed as endangered by the U.S. government under the Endangered Species Act.

The threatened extinction of the Saimaa ringed seal was long the focus of a major publicity campaign by the Finnish Association for Nature Conservation, and a poster depicting the seal has become a Finnish icon of nature conservation in general.

In 1983, the population was between 100 and 150 seals. In 2005, it was about 270, but as a result of two unfavorable breeding seasons, 2006 and 2007, the number dropped down to 260. In 2013, the population was estimated at just over 300 and the population numbers were in a slight growth. The number of breeding-aged females was 87.[15] It was thought that the immediate threat of extinction would be alleviated if the population grew to over 400 individuals.

In spring 2016, 79 pups were found, four of which were dead.[16]

In order to protect the Saimaa ringed seal, there are voluntary fisheries restrictions in a part of their living areas. The most important form of restriction is a ban on fishing nets from April 15 till the end of June in about 15% of the lake; nearly all fishing is recreational. Bycatch mortality has, however, remained high with estimated mortality of 20–30 seals annually, most of them pups of the same year.

In 2010 the European Union required Finland to do more to protect the seals, particularly from net fishing.[17] To reduce the by-catch mortality of seals aged over one year, the use of certain fishing methods has been banned since 2011, which included strong mesh nets, large fish traps, and fish-baited hooks, in the main part of the Saimaa ringed seal's habitat.[18]

In 2016, one Act and Mutual Agreement between authorities and owners of fishing waters replaced earlier two acts. The fishing co-operatives get 1.7 euros per hectare to ensure that fishing limitations are followed. Net fishing (except of vendace nets) is forbidden between mid-April and end of June in certain areas, which have been drawn at 5 km radius from nesting sites.[19]

Breeding success of Saimaa ringed seal depends on sufficient ice and snow cover. The loss of snow and ice caused by the ongoing climate change poses a direct threat to them. Human-made snowdrifts have proved to be successful in improving seals' breeding success during winters with poor snow conditions.[20] Snowdrifts were tested for three winters, and from 2014, they have been used regularly.[21][22] In addition, artificial lairs are also in development for winters when there is no snow on ice due to climate change.[23] Conservation experts expect to produce 100 of these boxes for dispersal and maintenance by the local citizenry.[23]

Recent estimates place the current population at between 420 and 430 individuals.[24]

The Saimaa ringed seal lives mainly in two Finnish national parks, Kolovesi and Linnansaari.[25] Strays have been seen in a much larger area, including Savonlinna centre.

Norppalive

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Norppalive (literally "Ringed Seal Live") is a live webcast of the Saimaa ringed seal produced by WWF.[26][27] It shows a live image of a place that is occasionally visited by a Saimaa ringed seal.[26] The purpose of Norppalive is to raise awareness of the Saimaa ringed seal.[28] In 2016, Norppalive gathered at its best 180,000 simultaneous viewers[26] and a total of more than two million viewers.[28] One of the most well-known ringed seals found in live broadcasts is Pullervo, which has gained the status of Finland's most famous Saimaa ringed seal.[26][29]

See also

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References

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  1. ^ Sipilä, T. (2016). "Pusa hispida ssp. saimensis". IUCN Red List of Threatened Species. 2016: e.T41675A66991678. doi:10.2305/IUCN.UK.2016-1.RLTS.T41675A66991678.en.
  2. ^ Strandberg, Ursula; Sipilä, Tero; Koskela, Jouni; Kunnasranta, Mervi; Käkelä, Reijo (2011). "Vertical fatty acid profiles in blubber of a freshwater ringed seal — Comparison to a marine relative". Journal of Experimental Marine Biology and Ecology. 407 (2): 256. Bibcode:2011JEMBE.407..256S. doi:10.1016/j.jembe.2011.06.021.
  3. ^ "Saimaa Ringed Seal". Retrieved 22 December 2018.
  4. ^ Palo, J.U. (2003). "Postglacial loss of microsatellite variation in the landlocked Lake Saimaa ringed seal". Conservation Genetics. 4 (2): 117–128. doi:10.1023/a:1023303109701. ISSN 1566-0621. S2CID 25621332.
  5. ^ a b "Suur-Saimaa". Järvi-meriwiki (in Finnish). Finnish Environment Institute. 9 March 2021. Retrieved 22 February 2023. Suur-Saimaa on usean toistensa yhteydessä olevien samapintaisten järvien muodostama suurjärvi. Sen yhteenlaskettu pinta-ala on 427 946,4 ha ja suurin syvyys 85,81 m. [...] Mantereen ja saarten rantaviivaa sokkeloisella Suur-Saimaalla on peräti 14 850 kilometriä. [Greater Saimaa is a great lake formed by multiple connected lakes that are at the same water level. Its total surface area is 427,946.4 hectares and its greatest depth is 85.81 meters. [...] The labyrinthine Greater Saimaa has as much as 14,850 km of coastline along its mainland and island shores.]
  6. ^ Kuusisto, Esko (1978). Suur-Saimaan vesitase ja tulovirtaaman ennustaminen (in Finnish). pp. 12–15.
  7. ^ a b c Kunnasranta, Mervi; Hyvärinen, Heikki; Häkkinen, Jani; Koskela, Jouni T. (March 2002). "Dive types and circadian behaviour patterns of Saimaa ringed sealsPhoca hispida saimensis during the open-water season". Acta Theriologica. 47 (1): 63–72. doi:10.1007/bf03193567. ISSN 0001-7051. S2CID 23840132.
  8. ^ a b c d e f Auttila M., Sinisalo T., Valtonen M., Niemi M., Viljanen M., Kurkilahti M., Kunnasranta M. Diet composition and seasonal feeding patterns of a freshwater ringed seal (Pusa hispida saimensis) Mar. Mamm. Sci., 31 (2015), pp. 45–65
  9. ^ Kunnasranta M., Hyvarinen H., Sipila T. and Koskela J. T. 1999. The diet of the Saimaa ringed seal Phoca hispida saimensis. Acta Theriologica 44: 443–450.
  10. ^ Niemi M, Auttila M, Viljanen M, Kunnasranta M. Home range, survival, and dispersal of endangered Saimaa ringed seal pups: Implications for conservation. Mar Mammal Sci. 2013;29: 1–13.
  11. ^ "Distribution, population size and reproductivity of the Saimaa ringed seal (Phoca hispida saimensis Nordq.) in Finland, 1980–84".
  12. ^ Sipila, Tero (January 1990). "Lair structure and breeding habitat of the Saimaa ringed seal (Phoca hispida saimensis Nordq.) in Finland". Retrieved 4 June 2018.
  13. ^ a b Hyvarinen, Heikki; Hamalainen, Esa; Kunnasranta, Mervi (July 1995). "Diving Behavior of the Saimaa Ringed Seal (Phoca Hispida Saimensis Nordq.)". Marine Mammal Science. 11 (3): 324–334. Bibcode:1995MMamS..11..324H. doi:10.1111/j.1748-7692.1995.tb00288.x. ISSN 0824-0469.
  14. ^ HYVÄRINEN, HEIKKI (August 1989). "Diving in darkness: whiskers as sense organs of the ringed seal(Phoca hispida saimensis)". Journal of Zoology. 218 (4): 663–678. doi:10.1111/j.1469-7998.1989.tb05008.x. ISSN 0952-8369.
  15. ^ Partio, Elina (2013-09-13). "Saimaannorpan kanta kasvussa".
  16. ^ "Saimaalta löytyi 79 kuuttia, mikä on ennätysmäärä". Maatalouden Tulevaisuus (in Finnish). 2016-04-15. Retrieved 2016-05-01.
  17. ^ Platt, John (10 May 2010). "E.U. orders Finland to protect critically endangered seals". Scientific American (Extinction Countdown blog).
  18. ^ "A New Protection Strategy for the Saimaa Ringed Seal, Due to Climate Change" (PDF). Metsähallitus - Natural Heritage Services, Eastern Finland. 2011. Archived from the original (PDF) on 2016-04-12. Retrieved 2016-05-01.
  19. ^ "Kalastusrajoitukset voimaan saimaannorpan suojelemiseksi". Ministry of Agriculture (in Finnish). 2016-04-14. Retrieved 2016-05-01.
  20. ^ "Human intervention can help endangered Saimaa ringed seal adapt to climate change". Science Daily. 2015-11-05. Retrieved 2016-05-01.
  21. ^ "Apukinoksen teko norpan pesinnän suojaksi on tarkkaa puuhaa - Katso video!". Länsi-Savo (in Finnish). 2014. Retrieved 2016-05-01.
  22. ^ "Saimaannorpan luonnonpesintä on vaarassa, apu kinosten kasaamisesta päätetään pian". hs.fi (in Finnish). 2016. Retrieved 2016-05-01.
  23. ^ a b "Inside the fight to bring the Saimaa ringed seal back from the brink of extinction". The Independent. 2022-08-14. Retrieved 2022-12-14.
  24. ^ "Few Saimaa seal pups lost this past winter". yle.fi. 30 April 2021. Retrieved 29 November 2021.
  25. ^ "Welcome to Linnansaari and Kolovesi National Parks". Järvisydän. 2016. Archived from the original on 2016-09-26. Retrieved 2016-05-01.
  26. ^ a b c d Eloranta, Ville (May 20, 2017). "Suomalaisten suosikkinorppa Pullervo palasi Norppalive-lähetykseen – tuhannet katsojat seuraavat hylkeen lekottelua kalliolla". Helsingin Sanomat (in Finnish). Retrieved May 19, 2021.
  27. ^ Norppalive – WWF
  28. ^ a b Vironen, Petri (May 10, 2017). "Supersuosittu Norppalive palasi verkkoon – "Jokainen uusi kävijä ja laskematta jäänyt verkko on bonusta"". YLE (in Finnish). Retrieved May 19, 2021.
  29. ^ Norppagalleria – WWF (in Finnish)
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