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Harbour Seal
Phoca vitulina
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The harbour seal is the most numerous and widespread marine
mammal on the north Pacific Coast. It is found close to shore
from Baja California to Japan. The subspecies of harbour seal
on the north Pacific Coast of North America is the Pacific
subspecies Phoca vitulina richardsi that ranges along
the coast from Baja California to Japan (Baird 2001). Pelage
colouration, dentition patterns, seasonal time of pupping and
mitochondrial and microsatellite DNA evidence suggests that
there might be several discrete populations on the Pacific
Coast (reviewed by Baird 2001).
In recent years, the harbour seal has become a component of a
flourishing whale watching industry but only a few decades
ago, a bounty was in place to cull seals. Baird (2001) has
reviewed the status of the harbour seal in Canada.
There is estimated to be at least 100,000 harbour seals in
British Columbia (Olesiuk 1999). This estimate was made by
counting seals at haul-outs and applying a correction factor
to account for seals underwater during the census. The choice
of correction factor introduces considerable error in the
estimate but the conclusion that seals are far more numerous
than in the 1970s is undeniable. Culling of seals occurred in
Canada under a bounty system that ended in 1969. Since then,
the population grew at about 12% annually and it is probably
now at its pre-cull level (Olesiuk et al 1990).
Most harbour seals mate as monogamous pairs but some
polygynous mating is also possible (Bigg 1981, Sullivan 1981,
Riedman 1990). Mating occurs in the water making observations
difficult. Pups are born earlier in the south than the north.
In Washington and southern British Columbia, females give
birth to a single pup in May or June, while in northern
British Columbia and southeast Alaska pupping occurs in June
and July. A pup about 80 cm long at birth will attain a length
of 1.9 m as an adult and males are about 13% larger than
females. The pups follow their mothers into the water soon
after birth. They are weaned at about three weeks of age and
females enter estrus a few weeks later. Females first breed
between 3 and 6 years of age (most at 5 years; Bigg 1969a,b).
Seals eat mostly fish but the diet includes many species such
as herring, salmon, midshipman, ling cod among others and
likely reflects local availability (Olesiuk 1993). Harbour
seals are eaten often by ‘transient’ killer whales (Baird and
Dill 1996, Watts 1993) and they are important predator of fish
(Yurk and Trites 2000).
References
Baird, R. W. 2001. The status of the harbour seal Phoca
vitulina in Canada. Canadian Field-Naturalist 115:
663-675.
Bigg,, M. A. 1969a. The harbour seal in British Columbia.
Fisheries Research Board of Canada Bulletin 172, Ottawa.
Bigg, M. A. 1969b. Clines in the pupping season of the harbour
seal, Phoca vitulina. Journal of Fisheries Resaerch
Board of Canada 26: 449-455.
Olesiuk, P.F. 1993. Annual prey consumption by harbour seals (Phoca
vitulina) in the Strait of Georgia, British Columbia.
Fisheries Bulletin 91: 491-515.
Olesiuk, P. 1999. An assessment of the status
of harbour seals (Phoca vitulina) in British Columbia.
Canadian Stock Assessment Secretariat Research Document -
1999/33.
Available at http://www.dfo-mpo.gc.ca/csas/Csas/publications/ResDocs-DocRech/1999/1999_033_e.htm
Olesiuk, P. F., M. A. Bigg and G. M. Ellis. 1990. An
assessment of the feeding habits of harbour seals (Phoca
vitulina) in the Strait of Georgia, British Columbia,
based on scat analysis. Canadian Technical Report of Fisheries
and Aquatic Sciences 1730, Nanaimo, BC.
Riedmann, M. 1990. The pinnipeds: seals, sea Lions, and
walruses. Univeristy of California Press, Berkeley, USA.
Sullivan, R. M. 1982. Agonistic behavior and dominance
relationships in the harbor seal Phoca vitulina.
Journal of Mammalogy 63: 554-569.
Yurk, H and A. W. Trites. 2000. Experimental attempts to
reduce predation by harbor seals of out-migrating salmonids.
Transactions of the American Fisheries Society 129:1360-1366.
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