The Davis Strait - DCE - Nationalt Center for Miljø og Energi

sonal communication 1984) varied within an area confined by approx. 55°
45'W – approx. 60° W and approx. 61° 50' N – approx. 63° 15' N (Bowen et
al. 1987: 286). It is likely that the number of polar bears occurring at the Davis
Strait hooded seal whelping patch during spring also varies from year to
year, depending among other factors on ice conditions in the Davis Strait
and the ability of the bears to reach the whelping patch from eastern Baffin
Island.
In recent years unusual occurrence of concentrations of harp seals (Pagophilus
groenlandicus) at the eastern edge of the Davis Strait pack ice has been reported.
In late January-early February large numbers of harp seals were observed
in the pack ice west of the town of Sisimiut (approx. 67° N) (Rosing-
Asvid 2008). Hence, variation in the distribution of prey including concentrations
of harp seals may also influence the spatial distribution and number
of polar bears within the assessment area.
Number: The most recent inventory of the Davis Strait subpopulation was
completed in 2007 resulting in an estimate is 2,142 polar bears (95% lognormal
CI 1811 – 2534) (Obbard et al. 2010).
Amstrup et al. (2007, 2008) incorporated projections of future sea ice in four
different ‘ecoregions’ of the Arctic, based on ten general circulation models
by the International Climate Change Panel (ICCP), into two models of polar
bear habitat and potential population response. One eco-region encompasses
the polar bear habitat with seasonal ice (‘the seasonal ice ecoregion’) – including
the Davis Strait – where sea ice usually is absent during the open
water period. One of the models (a deterministic ’carrying capacity model’)
predicted a 7-10% decrease in the polar bear population in the ‘seasonal ice
ecoregion’ approx. 45 years from now (22-32% decline approx. 100 years
from now), whereas the other model (quasi-quantitative ‘Bayesian network
population stressor model’) predicted extirpation of polar bears in this
ecoregion – including the Davis Strait – by the mid-2100s.
Conclusions: Polar bears from the Davis Strait subpopulation occur within
the assessment area during periods with sea ice. Satellite telemetry data
from the 1990s indicate that polar bears may occur in the assessment area
from November-December until sometime in spring (May-June), depending
on annual variability in sea ice cover. It is likely that the distribution and
number of polar bears from the Davis Strait subpopulation that occur at the
eastern edge of the Davis Strait pack ice to a certain extent are influenced by
the location of the Davis Strait hooded seal whelping patch and unusual occurrence
of harp seal concentrations.
Walrus, Odobenus rosmarus
General biology: The following life history traits are relevant to evaluation of
the potential effects on walruses from oil-related activities. An important
characteristic of walruses is that they are gregarious year round (Fay 1982,
1985), which means that impacts will concern groups rather than single individuals
(Wiig et al. 1996). Walruses are benthic feeders that usually forage
where water depths are less than approximately 100 m (Vibe 1950, Fay 1982,
Born et al. 2003); although they occasionally make dives to at least 200–250+
m depth, both inshore and offshore (Born et al. 2005, Acquarone et al. 2006).
They have an affinity to shallow water areas with suitable benthic food and
winter in areas without solid ice - i.e. where there is not 100% sea ice cover
(Born et al. 1995 and references therein). In western Greenland such habitat
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