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

Table 10.1.1. Overview of potential impacts from a single seismic 2D survey on VECs in the Davis Strait assessment area. See
section 4.9 for a summary of the VECs. It is important to note that a single seismic survey is temporary (days or a few weeks)
and that cumulative impacts of several simultaneous or consecutive surveys may be more pronounced. This assessment assumes
the application of current (2011) mitigation guidelines, see text for details.
VEC Typical vulnerable organisms
Population impact* - worst case
Displacement Sublethal effect Direct mortality
Pelagic hotspots copepods, fish larvae - insignificant (L) insignificant (L)
Tidal/subtidal zone none - - -
Demersal fish & offshore benthos Gl. halibut short term (L) insignificant none
Seabirds (breeding) none - - -
Seabirds (non-breeding) none - - -
Marine mammals (summer) baleen & toothed whales short term (L) insignificant (R) none**
Marine mammals (winter) bowhead, beluga, narwhal short term (L) insignificant (R) none**
* L = local, R = regional and G = global; ** For toothed whales permanent auditory damages can theoretically be lethal, but
death would occur long after the event of sound exposure. Here, this risk is defined as a sublethal effect.
The fishery at risk of impacts from seismic surveys in the assessment area is
the Greenland halibut fishery. There is a risk of a temporary displacement of
fish and consequently reduced catches from the trawling grounds. Although
the precise location of the Greenland halibut spawning grounds is not
known, the planning of seismic surveys in the suspected area should consider
avoiding overlap in the spawning period. The fishery of northern shrimp
and snow crab will probably not be affected.
Noise from drilling rigs
This noise has two sources, the drilling process and the propellers keeping
the drill ship/rig in position. The noise is continuous in contrast to the pulses
generated by seismic airguns.
Generally a drill ship generates more noise than a semi-submersible platform,
which in turn is noisier than a jack-up. Jack-ups will most likely not be
employed within the assessment area, due to water depths and the hazard
risk from drift ice and icebergs.
Whales are believed to be the organisms most sensitive to this kind of underwater
noise (Table 10.1.2), because they depend on the underwater
acoustic environment for orientation and communication and it is believed
that this communication can be masked by the noise. But also seals (especially
bearded seal) and walrus communicate when underwater. However, systematic
studies on whales and noise from drill rigs are limited. It is generally
believed that whales are more tolerant of fixed noise than noise from moving
sources (Davis et al. 1990), and auditory masking from boat noise has
been demonstrated for beluga whales and killer whales in Canada (Foote et
al. 2004, Scheifele et al. 2005). In Alaskan waters migrating bowhead whales
avoided an area with a radius of 10 km around a drill ship (Richardson et al.
1995) and their migrating routes were displaced away from the coast during
oil production on an artificial island; although this reaction was mainly attributed
to the noise from support vessels (Greene et al. 2004).
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