Last modified: Thursday September 24th, 1999 |
Other phocid seals
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Harp seal
Phoca groenlandica (Erxleben, 1777)
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Nomenclature
This species was originally by Fabricius in 1776, but the species
was described by Erxleben in 1777. Gray (1850) changed the name to Pagophilus
groenlandicus, but the species is now again included in the genus Phoca
by most. However, according to Rice (1998) the inclusion of a large number of species
in the genus Phoca is not admissible, which means the Pagophilus groenlandicus
would be the valid name for this species. Common
names that are also used to describe the harp seal are Greenland seal and
saddleback.
Appearance
Harp seals are 1.7m long and weigh 130 kg. Pups
measure 90-105 cm and weigh 6-10 kg at birth. Males are silvery grey with a black
head and a horseshoe-shaped band across the back and the flanks. Females have
a lighter head and also the "harp" is lighter and can be fragmented. Pups have a
silky white fur at birth and moult after 1 week. After moult they are silvery grey with
irregular dark and black spots.
The harp seal goes through a number of stages during its early development (Lavigne
and Kovacs, 1988):
Stage |
Age (days) |
|
Short description |
Newborn |
0 |
|
small, skinny, uncoordinated movements |
Yellowcoat |
1 |
|
dried up, yellowish |
Thin whitecoat |
4 |
|
white, growing, more coordinated movements |
Fat whitecoat |
7 |
|
end of weaning: half of body weight (30+kg) is stored fat |
Greycoat |
12 |
|
spotted, juvenile pelage can be seen underneath white fur |
Ragged-jacket |
21 |
|
moulting. white pelage is shed |
Beater |
25+ |
|
black-spotted juvenile pelage. The name refers to the poorly developed
swimming skills. They "beat" the water. |
Distribution
There are 3 different stocks: in the White Sea, at Jan Mayen and on
Newfoundland (2 substocks: Labrador and Gulf of St. Lawrence).
Feeding
Young harp seals feed mainly on euphasiids. Adults eat capelin, polar
cod, herring, cod and shrimp. They eat 1-5% of their body weight of fish per day.
The Northwest Atlantic harp seal population consumes and estimated 500,000
tonnes of capelin and 20,000 tonnes of herring per year. The total consumption for
this population can be as high as 2,000,000 tonnes per year (Ronald et al, 1982).
Population dynamics and life history
Females become mature at 5 years, males at 6-8 years. The
age of maturity might be density dependent. The pregnancy rate is over 90%.
Gestation lasts 11 months, including a 4 month delay of implantation (Ronald et
al (1982) mention a delay of implantation of 11 weeks, followed by a gestation of 7
months). Lactation lasts 8-12 days. In this period the pup grows at a rate of
about 2 kg/day. (Lavigne and Kovacs, 1988). First year mortality is 20-30%.
Longevity is about 30 years. The natural
mortality for adult is 8-10%.
Trophic relations
The harp seal competes with fin whales and minke whales for
capelin. Polar bears, killer whales and sharks are the main predators of this
species.
There appear to be some interactions with hooded seals, although there is probably
no competition for food. Kovacs et al (1997) reported the
birth of a harp X hooded seal hybrid in the Gulf of St. Lawrence.
Interactions
There is competition for capelin and herring with commercial fisheries. The harp
seals have been implicated in the decline of the Northern Cod stock. However, an
internation working group concluded that this is unlikely (Canadian Centre for
Fisheries Innovation, 1997).
Population size
Lavigne (1979) gives the following estimates for the different
stocks:
- White Sea: 500,000-700,000 (111,000-125,000 pups produced)
- Jan Mayen: 100,000 (25,000 pups)
- Newfoundland: 700,000-1,500,000.
This gives a total
population of 1.3-2.3 million. Lavigne et al (1982) arrive at a Newfoundland
population in 1975 of 630,000-790,000. Ronald et al (1982) find the following
abundances:
- White Sea: 600,000
- Jan Mayen: 100,000
- Newfoundland: less than 1 million.
Total population: less than 1.7 million.
Exploitation
This species is exploited under regulations of the International
Commission for Northwest Atlantic Fisheries (ICNAF).In the White Sea pups can be
harvested between 23. March and 30. April. Quota are 27,000 for Soviet natives and
14,000 for Norwegian vessels. At Jan Mayen, Norway can catch 15,000 pups
between 23. March and 5. May. In Newfoundland the quota for 1976 were: 52333
for Canadian vessels, 44667 for Norwegian vessels and 30,000 for Canadian land-based hunters.
Not included in the quota are catches by Japanese vessels, which
amount to about 7,000 per year.
Catch statistics for the Northwest Atlantic (Lavigne, 1999)
Year |
Canada reported |
Canada estimated |
Greenland reported |
Greenland estimated |
1994 |
52,916 |
63,571-93,509 |
57,905 |
115,810 |
1995 |
64,794 |
75,813-105,441 |
63,202 |
126,404 |
1996 |
242,262 |
274,968-342,405 |
50,626-67,886 |
101,252-135,772 |
1997 |
264,204 |
296,187-370,394 |
50,626-67,886 |
101,252-135,772 |
1998 |
282,070 |
315,918-397,719 |
50,626-67,886 |
101,252-135,772 |
Threats to the population
The main threats are over-exploitation of the seal
stocks and over-exploitation of the capelin and herring stocks.
References
- Bonner, W.N. (1982)
- Seals and Man. A study of interactions. University of
Washington Press, Seattle, 170pp.
- Bowen, W.D. (1985)
- Harp seal feeding and interactions with commercial fisheries
in the Northwest Atlantic.
in: Beddington, J.R., Beverton, R.J.H. and Lavigne, D.M.
(eds.): Marine Mammals and Fisheries, pp. 135-152,
George Allen & Unwin
(Publishers) Ltd, London
- Canadian Centre for Fisheries Innovation (1997)
- Report of the Workshop on harp seal-fishery interactions in the
Northwest Atlantic: Towards research & management actions. 43pp.
Canadian Centre for Fisheries Innovation and Memorial University of Newfoundland.
(can be downloaded from the International Marine Mammal
Association Web site)
- King, J.E. (1983)
- Seals of the world, 2nd edition.
British Museum (Natural History),
London and Oxford University Press, Oxford, 240pp.
- Kovacs, K.M., Lydersen, Chr., Hammill, M.O., White, B.N., Wilson, P.J. and Malik, S. (1997)
- A harp seal X hooded seal hybrid.
Mar. Mamm. Sci. 13(3): 460-468
- Lavigne, D. (1979)
- Harp Seal.
in: Mammals in the Seas, volume II: pinniped
species summaries and report on sirenians.
FAO Fisheries Series No. 5, Vol II, pp.
76-80
- Lavigne, D.M. (1999)
- Estimating total kill of Northwest Atlantic harp seals, 1994-1998
Mar. Mamm. Sci. 15(3): 871-878
- Lavigne, D.M., Innes, S., Kalpakis, K., Ronald, K. (1982)
- An aerial census of
Western Atlantic harp seals (Pagophilus groenlandicus) using ultraviolet
photography.
in: Mammals in the Seas, Volume IV: small cetaceans, seals, sirenians
and otters.
FAO Fisheries Series, No. 5, vol. IV, pp. 295-302
- Lavigne, D.L. and Kovac, K.M. (1988)
- Harps and hoods.
University of Waterloo Press, 174pp.
- 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.
- Ronald, K., Healey, P.J. (1981)
- Harp Seal, Phoca groenlandica Erxleben, 1777.
in:
Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2:
Seals, pp. 55-87,
Academic Press Inc., Ltd, London
- Ronald, K., Healey, P.J., Fisher, H.D. (1982)
- The harp seal, Pagophilus
groenlandicus.
in: Mammals in the Seas, Volume IV: small cetaceans, seals,
sirenians and otters.
FAO Fisheries Series, No. 5, vol. IV, pp. 267-293
About the pictures
These pictures were taken at the National Aquarium in Baltimore, in November
1997. This seal was on display there, after being rehabilitated. It was not
released because it has eye problems.
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Nomenclature
In 1783, Zimmerman described this seal and named it Phoca
fasciata. In 1873 Gill put this seal in a separate genus and named it Histriophoca
fasciata. Burns and Fay included it again in the genus Phoca in 1970, but according
to Rice (1998) this is not admissible. This seal is
also called the banded seal.
Appearance
This seal measures on average 155-165 cm (maximum 190 cm
(Popov, 1982)) and weighs 70-80 kg (maximum 100 kg (Popov, 1982)). At birth,
pups are 80-90 cm long and weigh 9-10 kg. Males are dark chocolate brown with
white to yellowish bands around the neck, flippers and hind part. Females have a
similar colouration, but less distinct. Pups are born with a white lanugo, which after
the moult is replaced by coat with a blue-grey dorsal and siver-grey ventral.
Distribution
This seal lives near the pack ice, in the Sea of Okhotsk and in the
Bering Sea.
Feeding
The ribbon seal feeds primarily on bottom invertebrates, fishes like
pollack, eelpoutand arctic cod as well as cephalopods.
Population dynamics and life history
Females are mature when they are 2-4 years old and males
when they are 3-5 years (Popov (1982) gives 4-5 and 5-6 years respectively). The
pregnancy rate is 85%. Gestation lasts 10-11 months. The longevity is anywhere
between 22 and 26 years. First year mortality is 44% and the mortality rate for older
age classes is on average 11.2%.
Trophic relations
There may be competition with other pinniped species, but there
are no data on that. Possible predators include the killer whale and the polar bear.
Interactions
None known.
Population size
Stirling (1979) estimates the Bering Sea population at 100,000
and the Okhotsk Sea population at 140,000. Popov (1982) arrives at estimates of
60,000 for the Bering Sea and 133,000 for the Okhotsk Sea. The population may be
declining.
Exploitation
In the Alaska only subsistence hunting occurs. 100-250 animals are
taken there per year. In the USSR a permit system is in effect, which allows the
harvest of 3,000 ribbon seals in the Bering Sea and of 3,500 seals in the Sea of
Okhotsk. In the past this species has been over-exploited.
Threats to the population
The main threat lies in over-exploitation. This species
has been over-exploited in the past and may very well still be over-exploited.
References
- Burns, J.J. (1981)
- Ribbon Seal Phoca fasciata Zimmermann, 1783. in: Ridgway,
S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2: Seals,
pp. 89-109, Academic Press Inc., Ltd, London
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History),
London and Oxford University Press, Oxford, 240pp.
- 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. (1979)
- Ribbon Seal. in: Mammals in the Seas, volume II: pinniped
species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp.
81-82
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Appearance
The males of this species are 2.5m long and weigh about 300
kg. Females measure 2.2m and weigh about 160 kg. Pups are 100-120 cm
long and weigh 10-15, maybe even over 20 kg (Popov, 1982). The hooded seals are
grey, with black irregular patches. The males have an inflatable crest, which is an
enlargement of the nasal cavity. To inflate it, they close the nostrils. (This is not
necessary for the proboscis of elephant seals). Hooded seal pups shed the light grey lanugo
before birth. At birth they appear blue-grey on the back and silver-grey on the sides and
underneath (Lavigne and Kovacs, 1988).
Distribution
Hooded seals are migratory animals. They can be found throughout
the Northern Atlantic. There are a few distinct breeding sites: the West Ice (Jan
Mayen region), the Davis Strait at 64°N, the Front (Newfoundland) and the Gulf of
St. Lawrence. Moulting takes place on 2 locations: in Denmark Strait (Greenland)
and off Greenland at 72-74°N.
Feeding
Adult hooded seals feed on squid, redfish and Greenland halibut. Pups
feed mainly on capelin, polar cod and amphipods.
Population dynamics and life history
Female are meture at the age of 3. The onset of maturity in
males is unknown. The pregnancy rate is 95%. Gestation lasts 11.7 months,
including a delay of implantation of more than 4 months. Lactation lasts about 4 days.
The pups grow about 5 kg/day during lactation.
Natural mortality is estimated at 7-15% for adults. The maximum longevity
is probably about 35 years (Lavigne and Kovacs, 1988).
Trophic relations
Although they live in the same area as the harp seal, Phoca
groenlandica, there is probably no competition between harp seals and hooded
seals, because they forage in different areas and on different species.
There appear to be some interactions, though. Kovacs et al (1997) reported the
birth of a harp X hooded seal hybrid in the Gulf of St. Lawrence.
Predators of the hooded seal are sharks and polar bears.
Interactions
No interactions with fisheries have been recorded.
Population size
For some areas photo surveys have been carried out. In the Davis
Strait 42,000 animals were counted.In the Front area, 77,000 females were counted
and from that a pup production of 38,000 was estimated. On the West Ice 225,000
seals were counted. On the molting site in Denmark Strait 230,000 seals were
counted. Popov (1982) estimates the total hooded seal population at 500,000-600,000.
Exploitation
There is a quota system for the harvest of this species. 30% of the
total kill consists of adult seals, of which 60-70% are females. The 1974-1982 yearly harvest
rates were: 30,000 for Jan Mayen and 15,000 for Newfoundland. For 1984-1988 a yearly quota
of 2,340 was set for Newfoundland. Actual catches were lower.
Threats to the population
There is a serious risk of over-exploitation, especially
on Jan Mayen. Especially the rather large portion of adult females in the total
harvest poses a serious threat to the population.
References
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History),
London and Oxford University Press, Oxford, 240pp.
- Kovacs, K.M., Lydersen, Chr., Hammill, M.O., White, B.N., Wilson, P.J. and Malik, S. (1997)
- A harp seal X hooded seal hybrid. Mar. Mamm. Sci. 13(3): 460-468
- Lavigne, D.L. and Kovac, K.M. (1988)
- Harps and hoods.University of Waterloo Press, 174pp.
- 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
- Reeves, R.R., Ling, J.K. (1981)
- Hooded Seal Cystophora cristata, Erxleben, 1777.
in: Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2:
Seals, pp. 171-194, Academic Press Inc., Ltd, London
- Sergeant, D.E. (1979)
- Hooded Seal. in: Mammals in the Seas, volume II: pinniped
species summaries and report on sirenians. FAO Fisheries Series No. 5, Vol II, pp.
86-89
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Nomenclature
There are 2 subspecies commonly recognized, each with its own
geographical range: E.b. barbatus (Erxleben, 1777) and E.b. nauticus (Pallas,
1811).
Appearance
The bearded seal is 225-270cm long and weighs 275-340 kg. Pups
are 87-120 cm long and weigh 25-43 kg. Bearded seals are grey, with occasionally
a brown face and neck. They have moustachial whiskers, which curl in tight spirals.
Their flippers are rather square. Pups are dark with white patches on the back and
on the flippers. Bearded seals have 4 mammary glands.
Distribution
The bearded seal lives circumpolar with a northern limit at 80-85°N.
They do not migrate. E.b. barbatus is found from the Laptev sea westwards to the
Hudson bay. It can be found as far south as the Gulf of St. Lawrence. E.b. nauticus
ranges from the Laptev Sea eastwards to the Barents sea and the Canadian Arctic,
upto Baffin Island. It can be found as far south as the Sea of Okhotsk or even
Hokkaido.
Feeding
The bearded seal feeds mainly only bottom invertebrates, such as
crustaceans, mollusks, whelks and polychaets, but also takes sculpin, flounder and
polar cod.
Population dynamics and life history
Females reach maturity at ages 5-6; males at 6-7 years. The
pregnancy rate in Alaska is 85% and in the USSR 75% (Popov, 1982). Gestation
lasts 10-11 months including a delay of implantation of 2-3 months. Lactation
lasts 12-18 days. Mortality rates are unknown. Only for the Okhotsk Sea the first
year mortality is known: 22% (Popov, 1982)
Trophic relations
There is no known competition. The main predator is the polar
bear. Occasionally killer whales will take bearded seals.
Interactions
There is no interaction with fisheries. There is a potential for
disturbance from oil explorations.
Population size
Complete data on abundance are not available. The Northern
Pacific population (Laptev Sea, Chukchi Sea, Bering Sea, Okhotsk Sea and Japan)
has been estimated to consist of 300,000 to 450,000 animals. Popov (1982) gives
an estimate for the Okhotsk Sea of 180,000-200,000 and for the Bering Sea of
250,000, which would mean that the Pacific population is over 450,000 animals.
There are no estimates for the Atlantic population.
Exploitation
There have been quota set for the Okhotsk Sea (5,000) and the
Bering Sea (3,000). These quota are for land-based hunters. Ship-based sealing is
prohibited. The annual kill in Norway is 2,000-3,000 seals. There are no records for
Canadian sealing. There is a considerable loss during the hunt, because bearded
seals sink when dead. In Alaska natives can hunt bearded seals without permits.
They may take as much as 6,000 seals. There is no harvest allowed in the Barents
Sea and the White Sea.
Threats to the population
There is a potential for over-exploitation in certain areas.
References
- Burns, J.J. (1981)
- Bearded Seal Erignathus barbatus, Erxleben, 1777. in:
Ridgway, S.H. and Harrison, R.J. (eds.): Handbook of Marine Mammals, vol. 2:
Seals, pp. 145-170, Academic Press Inc., Ltd, London
- King, J.E. (1983)
- Seals of the world, 2nd edition. British Museum (Natural History),
London and Oxford University Press, Oxford, 240pp.
- 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
- Stirling, I., Archibald, R. (1979)
- Bearded Seal. in: Mammals in the Seas, volume II:
pinniped species summaries and report on sirenians. FAO Fisheries Series No. 5,
Vol II, pp. 83-85
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