Last modified: Thursday September 24th, 1999

Ringed seals

Ringed seal

Phoca hispida (Schreber, 1775)

Nomenclature

Originally this species was referred to as Pusa hispida. Pusa is now considered to be a subgenus of Phoca by many. However, Rice (1998) states that the inclusion of a large number of species in the genus Phoca is not admissible and therefor the genus Pusa (which includes the ringed seal, the Caspian seal and the Baikal seal) is a valid genus. Several subspecies have been recognized, each with their own specific range. These are: Phoca hispida hispida (Schreber, 1775), Phoca hispida ochotensis (Pallas, 1811), Phoca hispida krascheninikovi (Naumov and Smirnov, 1936), Phoca hispida botnica (Gmelin, 1785), Phoca hispida ladogensis (Nordquist, 1899) and Phoca hispida saimensis (Nordquist, 1899). The latter two will be dealt with separately.

Appearance

The ringed seal measures from 85 to 160 cm and weigh 40 to 90 kg. Males are usually slightly larger than females. Pups are 55-65 cm at birth and weigh 4-5 kg. The color of the coat is dark grey with a grey to black dorsal with oval white rings. The ventral side is light grey. Pups are born with a white lanugo and moult after 3-4 weeks.

Distribution

Phoca hispida hispida
Arctic coasts of Europe, the USSR, Canada and Alaska, including Nova Zemlya, Spitsbergen, Greenland and Baffin Island.
Phoca hispida krascheninikovi
North Bering Sea
Phoca hispida ochotensis
Kamchatka, Okhotsk Sea and southward to 35°N, along the Japanese Pacific coast.
Phoca hispida botnica
Baltic Sea, Gulf of Bothnia and Gulf of Finland.

Feeding

The ringed seal is an opportunistic feeder, feeding on benthic, nektonic and planktonic organisms. In winter a large portion of the diet is taken up by polar cod, in summer by crustaceans and invertebrates.

Population dynamics and life history

The ringed seal females become mature at the age of 5-8, males at 6-8. The pregnancy rate is 80-95%. Popov (1982) mentions pregnancy rates of 70% for Phoca hispida hispida, 80% for Phoca hispida ochotensis and 73% for Phoca hispida krascheninikovi. Gestation lasts 10½-11 months, including a delay of implantation of 3½ months. The longevity is 46 years. The overall annual mortality is 15%. The annual mortality for all age classes except pups is 9%.

Trophic relations

There is an overlap in range and food choice with the bearded seal,Erignathus barbatus, and therefore a potential competition. There is extensive predation on the ringed seal by polar bears, but also by the polar fox, the killer whale and occasionally the walrus, Odobenus rosmarus.

Interactions

Especially in the Baltic Sea the ringed seal is a victim of pollution. High levels of PCB has caused uterine occlusions, leading to infertility (Helle et al, 1976). Exploration for oil in the Arctic often leads to disturbance of the seals.

Population size

The world population of the ringed seal is estimated to be 6-7 million animals. The population of Phoca hispida hispida is estimated to be 712,000. The population of Phoca hispida ochotensis is about 800,000-1,000,000. Popov (1982) estimated the population of Phoca hispida krascheninikovi at 70,000-80,000. Frost and Lowry (1981) mention a population size for Phoca hispida botnica of 10,000-50,000. In the early 1980's however, this population was no larger than 10,000 (Helle (1983), Halkka (1987)). The population in 1988 is estimated at 6,000-9,000 (Helle, pers. comm.). In 1995, the Baltic population was estimated to be around 6,000 seals, 4,000 of which live in the Bothnian Bay. The Gulf of Finland population is considered endangered at 200-300 animals (Halkka, pers. comm.)

Exploitation

The total annual Soviet-American harvest is between 12,000 and 16,000 seals. Popov (1982) mentions harvests of 7,000 for the Sea of Okhotsk, 2,000-3,000 for the Bering Sea and 3,500 for the White Sea. In Greenland the annual kill is 40,000-70,000. The Maximum Sustainable Yield (MSY) level is probably around 8%. Until 1989, a small number of seal could be in the Baltic Sea. Hunting ringed seals in now prohibited in Finland (Keränen and Soikkeli, 1989).

Threats to the population

The population in general is not in danger. However especially in the Baltic, the population is under pressure, due to the high level of pollution.

References

Frost, K.J., Lowry, L.F. (1981)
Ringed, Baikal and Caspian seals, Phoca hispida Schreber, 1775, Phoca sibirica Gmelin, 1788, Phoca caspica Gmelin, 1788. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 29-53, Academic Press Inc., Ltd, London
Halkka, A. (1987)
Hallikallioilla. Suomen Luonto 46(5): 20-23
Helle, E. (1983)
Hylkeiden elämää. Kirjayhtymä, Helsinki, 171pp.
Helle, E., Olsson, M., Jensen, S. (1976)
PCB levels correlated with pathological changes in seal uteri. Ambio 5(5): 261-263
Keränen, S., and Soikkeli, M. (1989)
Ajojäällä syntynyt, Forssan Kustannus, Forssa, Finland, 127pp.
Popov, L.A. (1982)
Status of the main ice-living seals inhabiting inland waters and coastal marine areas of the USSR. in: Mammals in the Seas, Volume IV: small cetaceans, seals, sirenians and otters. FAO Fisheries Series, No. 5, vol. IV, pp. 361-381
Rice, D.W. (1998)
Marine mammals of the world - Systematics and distribution
Society of Marine Mammalogy Special Publication Number 4, 231 pp.
Stirling, I., Calvert, W. (1979)
Ringed Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 66-69

Back to Table of Contents Back to the Table of Contents

Ladoga seal

Phoca hispida ladogensis (Nordquist, 1899)

Appearance

Adult Ladoga seals are 150 cm long and weigh 60-70 kg. Pups are 50-60 cm at birth and weigh 4-5 kg. There are 4 different types of Ladoga seal coats (Popov, 1979). 47% of the seals has a dark brown coat with light ring-shaped patterns; 29% has a dark brown coat with light vein-like patterns; 17% has a light coat with a dark dorsal belt and ill-defined rings and brown spots; the coat of the other 7% is not described by Popov.

Distribution

This seal is only found in Lake Ladoga in Karelia (Russia).

Feeding

The fishes this species mainly feeds on are smelt, ruffe, burbot and cisco.

Population dynamics and life history

Females reach maturity at the age of 4-5, males at the age of 6-7. Other parameters are unknown, except the lactation time, which is about 5 months.

Trophic relations

There are no species in the lake competing with the Ladoga seal. There are no natural predators.

Interactions

There is a commercial fishery for smelt and cisco, but no interactions of the seals with this fishery is recorded. Also an increase in fishing effort has not affected the seal population (Yablokov, 1985).

Population size

The population is estimated at 10,000-12,000 seals and apparently stable. Helle (pers. comm.) reports a population size of 10,500-12,500 with a tendency to increase.

Exploitation

There is a catch quotum set at 500 seals per year. The average annual catch is between 150 and 200 animals. The catch is allowed only for fur and oil. No recreational hunting is allowed and there is no bounty system.

Threats to the population

None.

References

Frost, K.J., Lowry, L.F. (1981)
Ringed, Baikal and Caspian seals, Phoca hispida Schreber, 1775, Phoca sibirica Gmelin, 1788, Phoca caspica Gmelin, 1788. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 29-53, Academic Press Inc., Ltd, London
Popov, L. (1979)
Ladoga Seal. in: Mammals in the Seas, volume II: pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp. 70-71
Yablokov, A. (1985)
Marine mammal-fishery interactions in the Baikal and Ladoga Lakes and in the Caspian and White Seas. in: Beddington, J.R., Beverton, R.J.H. and Lavigne, D.M. (eds.): Marine Mammals and Fisheries, pp. 106-110, George Allen & Unwin (Publishers) Ltd, London

Back to Table of Contents Back to the Table of Contents

Saimaa seal

Phoca hispida saimensis (Nordquist, 1899)

Appearance

The Saimaa seal is similar in appearance as the Baltic ringed seal, but a bit smaller and darker in color.

Distribution

The Saimaa seal is found only in Lake Saimaa in South-East Finland. There are 2 main breeding areas in the lake (Linnansaari and Kolovesi).

Feeding

This seal feeds mainly on shoaling fish.

Population dynamics and life history

The Saimaa seal reaches maturity between the ages 3 and 7 years. Lactation lasts 3-6 weeks. Longevity is 40 years. Mortality rates and pregnancy rates are not recorded. An estimated 40-60% of the seals is not mature (Sipilä, 1991).

Trophic relations

Since this species lives rather isolated, there is no real competition and there are no natural predators.

Interactions

The main interference of humans with the Saimaa seal consists of disturbance (especially by recreational snowmobiles in winter that disturb the pups), pollution and habitat destruction by development on the shores of Lake Saimaa.

Population size

Helle (1983) estimated the population at 100-150 animals. Sipilä and Hyvärinen (1988) estimated the population at 150-160 seals and according to Helle (pers. comm.) the 1988 population was between 160 and 180 seals. Sipilä (1991) estimated the 1991 population at the same level. Of those seals, there are 38-40 sexually mature females. The number of pups born each year ranges from 18-26 (Sipilä, 1991) For 1995, the population was estimated at over 200 seals (Halkka, pers. comm.)

Exploitation

This species has been protected since 1955. To prevent incidental kill of this rare seal, fisheries are banned from the breeding areas.

Threats to the population

Despite the preventive measures, there is occasional net entanglement of the seals. Pollution, especially with organochlorines still poses a threat to this population. With the increased boat traffic and increased tourism there is an increase of disturbance. An increase in the amount of summer cottages around the lake can lead to habitat destruction. A recent threat is the water level control in the lake for the power plant. This can cause the breaking of the ice in the breeding season, with disastrous effects for the newborn pups. An overall increased pressure on the lake may reduce the room for the seals.

References

Frost, K.J., Lowry, L.F. (1981)
Ringed, Baikal and Caspian seals, Phoca hispida Schreber, 1775, Phoca sibirica Gmelin, 1788, Phoca caspica Gmelin, 1788. in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals, pp. 29-53, Academic Press Inc., Ltd, London
Helle, E. (1983)
Hylkeiden elämää. Kirjayhtymä, Helsinki, 171pp.
Sipilä, T., Hyvärinen, H. (1988)
Saimaannorpilla on toivoa - aktiivinen suojelu tehoaa. Suomen Luonto 47(4): 21-25
Sipilä, T. (1991)
Saimaanhyljealueiden suojelutavoitteet. Maailman Luonnon Säätiön WWF Suomen Rahaston Raportteja Nro 5, 82pp + 7 maps (in Finnish with summaries in Swedish and English)

Back to Table of Contents Back to the Table of Contents

Back to the Phocid Seal Page Back to the Main Page