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

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both until the end of the beluga whale hunt and the period of occupation of
especially important beluga whale habitats. Some particularly important beluga
whale areas were even completely closed for surveys.
In the NERI guidelines for seismic surveys (Boertmann et al. 2010) some important
issues to consider in assessing the impacts of seismic surveys were
listed:
• The species that could be affected; as tolerance to seismic surveys varies
between species
• The natural behaviour of these species when surveys are taking place.
Disturbance varies according to species' annual cycles, e.g. the degree of
sensitivity of animals engaged in mating and calving or those feeding or
migrating.
• The severity and duration of impact. Even a strong startle reaction to an
approaching survey vessel may have only a small total impact on the animal
whereas a small, but prolonged (days or weeks) disturbance to feeding
behaviour could have a much greater impact.
• Total number of animals likely to be affected. It is not possible to conduct
seismic surveys in the Arctic without affecting marine mammals at all.
The number of animals likely to be affected should be assessed in relation
to the size of the population, local stocks and season.
• Local conditions for sound transmission, such as hydrographic and
bathygraphic conditions, may result in highly unusual sound transmission
properties. Potential consequences of these effects should be included
in the assessment.
When planning surveys efforts should be made to minimise the overall exposure
to the degree possible by using the smallest airgun array that enables
collection of the data needed. Total exposure is a complex function of the
number of animals exposed, the time each animal is exposed and the sound
level each animal experiences. Nevertheless, reducing any of these three parameters
would reduce the total exposure, so the possibility of reducing one
or more factors should be considered in the planning phase.
Conclusions on disturbance from seismic noise (Table 10.1.1)
The VECs most sensitive to seismic noise in the assessment area are the baleen
whales, minke, fin, blue and humpback, and toothed whales such as
sperm and bottlenose whales. These may be in risk of being displaced from
critical summer habitats. A displacement will also impact the availability
(for hunters) of whales if the habitats include traditionally hunting grounds.
Narwhals, beluga whales, bowhead whales and walruses are also sensitive
to seismic noise, but their occurrence will only overlap with seismic surveys
during winter.
As seismic surveys are temporary, the risk of long-term impacts is low. But
long-term impacts have to be assessed if several surveys are carried out
simultaneously or in the same potentially critical habitats during consecutive
years (cumulative effect). There is a small risk of long-term effects for
toothed whales suffering permanent auditory damage caused by critical exposure
to seismic noise.