All activity relating to off-shore
oil and gas in the Irish sea is currently limited
to exploration, rather than exploitation. Factors
that could influence bottlenose dolphins within the
cSAC in the exploratory and exploitation phases are
considered here, although the latter is a wholly
unknown area at present.
a. Extent
of activity
i. Within the site
One block within the cSAC has been
licensed for exploration for oil and gas by the DTI.
Seismic survey was carried out by ARCO in the early
1990s who have subsequently relinquished their license.
There is currently no exploitation of oil and gas
resources in the southern Irish sea.
ii. Adjacent to the site
All exploration activity has been
or is being undertaken in blocks that lie to the
north-west and south of the cSAC. Current levels
of exploratory activity, ranging from seismic shooting
to drilling in areas adjacent to the cSAC are low.
Recently several oil companies holding exploration
licenses for blocks within the bay have sought to
surrender these to the DTI. In particular this means
that whereas oil companies were previously required
to conduct exploration drills as a condition of their
license they are no longer required to do so where
there are sufficient economic and geological reasons
not to.
b. Mechanisms
for effects on the features
i. Exploration
Seismic survey of the sea
bed.
Seismic survey essentially involves
the use of compressed air to generate high energy
sounds, typically ranging between 10 and 200 Hz.
Seismic shooting takes place via an array of air
guns aimed at the sea bed. Intensive low frequency
sounds penetrate the sea bed and are reflected back
by different rock-types. The reflected sound waves
are received by arrays of hydrophones, and reveal
subsurface geological formations. During firing,
high amplitude pulses lasting for ca. one second
are emitted every 5-15 seconds. Water is an excellent
conductor of sound, and sound (from man-made and
natural sources) travels considerable distances through
the water column. Seismic impulses travel large distances,
beyond the area targeted for seismic survey. Small
cetaceans have highly sensitive hearing, necessary
for echolocation. Their hearing covers a very broad
band width, and there is some overlap between sound
frequencies emitted during the seismic activity and
the hearing range of dolphins.
Research and monitoring carried
out in the Irish sea and elsewhere suggests that
seismic testing can adversely affect small cetaceans
in the following ways:-
-
Direct effects: Possible
damage to hearing, e.g. from a sudden burst
of seismic activity at close range; disruption/disturbance
to normal behaviour patterns e.g. temporary
evacuation of the area effected by seismic
testing [135] . See ‘Disturbance’.
-
Indirect effects: Possible
impact on prey
species (e.g. fish) resulting in temporary
redistribution in or changes in the behaviour
of shoaling fish [136] .
Since all seismic activity has
been/is being conducted outside the cSAC boundary,
any effects on bottlenose dolphins using the cSAC
are likely to derive from exploration in licensed
blocks adjacent to the cSAC. The significance of
any such impacts would be determined (in part at
least) by the distance between the animals and the
point-source of activity during the seismic survey.
See ‘Disturbance ’, page 55.
Shipping movements
In instances where exploratory
activity moves beyond seismic survey, i.e. drilling,
there is likely to be an increased level of localised
shipping movements, associated with supplying the
temporary drill rig (which could be on board a ship,
or a "jack-up" rig). Activity may be highly
localised, and of a temporary nature, whilst test
drilling is in progress. It is unlikely that the
area within the cSAC would be directly affected,
however the dolphins could be indirectly affected
by:-
Noise generated by shipping associated
with drilling activity. See ‘Disturbance ’.
-
Pollution, e.g. from
accidental spillages of fuel; rubbish; sewerage;
bunkering/supply of drilling vessels/rigs with
fuel (accidents during fuel transfer). See ‘Pollution’.
-
Collisions between shipping
and dolphins. See ‘Collisions’.
Drilling
All exploratory drilling has been
carried out, or is being carried out in areas to
the west and south of the cSAC. Influences on bottlenose
dolphins could arise from the following:
-
Pollution, e.g. oily
water discharges, oil or fuel discharges/spillage's
e.g. from rigs, well-heads or during bunkering
operations (see above). Localised contamination
of the sea bed as a result of disposal of drill
cuttings and muds. Sewerage and litter. See ‘Pollution’ and ‘Entanglement & Ingestion’.
-
Noise from drills. Sustained
noise pollution from drilling activities could
possible induce changes in dolphin behaviour
in the vicinity of the rig, and further a field.
See ‘Disturbance ’.
ii. Exploitation
The range of factors that could
influence bottlenose dolphins within the cSAC should
exploration be followed by development and exploitation
of oil and/or gas reservoirs in the vicinity of the
cSAC are broadly similar to those above. They include:
-
Pollution, from shipping
associated with servicing of rigs, the rigs
themselves, well-heads, pipelines and other
infrastructure associated with extraction and
movement of hydrocarbons, e.g.:
-
Contamination of the
sea bed by drill cuttings and muds.
-
Noise from shipping associated
with servicing of rigs; drilling operations
-
Collisions between dolphins
and shipping.
-
Catastrophic events:
it is possible that a "blow-out" on
a rig could have an effect on bottlenose dolphins
in the cSAC, e.g. through initial noise and/or
any resultant pollution and cleanup operation.
Any actual impacts from
the factors listed above would depend on a number
of variablese.g. the distance between the drilling
operations and the seaward boundary of the cSAC,
the locations of dolphins at the time of any incident
likely to impact on them, and their subsequent behaviour,
as well as the nature of individual incidents such
as pollution.
c. Management
response
The mechanisms by which oil and
gas exploration/exploitation could affect the feature
are, for the most part, reasonably well understood.
There is, however, no evidence to suggest that oil
and gas exploration is having an effect at present.
i. Rationale
The absence of oil and gas exploration
within the cSAC, together with the relatively low
levels of activity in neighbouring "blocks" that
have been licensed by the DTI for exploration suggest
that, at present, this is not a significant factor
influencing the feature in the cSAC. This would appear
likely to decrease following recent exploration pull
outs by Marathon and Chevron the two companies with
the largest holdings in the southern Irish Sea.
The bottlenose dolphins
that use the cSAC are highly mobile, and (probably)
range throughout the Cardigan Bay/southern Irish
Sea areas. Oil and gas exploration & exploitation
together with associated activities, e.g. shipping
could have a significant influence on the dolphins
that use the cSAC, even though these activities are/would
be taking place outside the cSAC. Bottlenose dolphins
are potentially "at risk" from disturbance
caused by noise (seismic shooting in particular,
but also noise caused by shipping and drilling) and
from oil and other forms of pollution. Increases
in shipping movements may also put individual animals
at risk from collisions.
Oil and gas exploration (and
any subsequent exploitation) in waters adjacent to
the cSAC could give rise to concern: risks of disturbance,
direct effects on individual animals from pollution,
collisions etc. and degradation of the habitat could
become significant. Future licensing rounds and seismic
surveys proposals should be monitored, and competent
Authorities should ensure that all potential impacts
on the feature and the habitat within the cSAC are
properly addressed in EIAs and via the significance/appropriate
assessment provisions in the 1994 Habitats Regulations
(see ‘Plans
and Projects’,). Competent Authorities should
also satisfy themselves that oil spill and other
emergency contingency plans adequately address the
sensitivity of the cSAC and the requirement to protect
the habitat as well as the feature of European importance.
Surveillance and/or monitoring of the influences
of this factor can only be carried out on a reactive
basis, i.e. when exploratory or exploitative activities
are notified/planned and then carried out. General
surveillance of dolphin activity numbers and distribution
within and adjacent to the cSAC should be established.
Data collected will help to provide the information
required for impact assessment.
ii. Type of response
F1 :
The activity constitutes a plan or project.
iii. Actions,
including links to other policies/plans/measures
-
Ensure, that EIAs and
appropriate assessments under the 1994 Habitats
Regulations are carried out, of all potential
direct and indirect impacts of off-shore oil
and gas exploration/exploitation.
-
Ensure that oil spill
and other emergency contingency plans adequately
address the requirement to protect the bottlenose
dolphin and its habitat in so far as they can.
-
In the event of a marine
pollution incident within the cSAC, or which
could threaten the cSAC, ensure that appropriate
consideration is given by the Environment Group
to the requirements/sensitivities of bottlenose
dolphins, and that this is reflected in the
advice give to any marine or other response
centre(s).
[135]
Goold, J.C. 1996. Acoustic assessment of populations
of common dolphin Delphinus delphis in conjunction
with seismic surveying. J. Mar.Biol.Ass. UK
76:811-820.
[136]
Dalen, J. and Knutsen, G.M. 1987. Scaring effects
on fish and harmful effects on eggs, larvae and
fry by offshore seismic exploration. In Merklinger,
H.M. (Ed). Progress in Underwater Acoustics. Plenum
Publishing Corp.
Engas, A., Lokkeborg, S. , Ona, E. & Soldal,
A.V. 1993. Effects of seismic shooting on catch
availability of cod and haddock. Institute of
Marine Research, Norway Fisken og Havet, No. 9.
