Environmental Statement - Maersk Oil

Balloch Field Development Environmental Statement
Section 3 Baseline Environment
3.6.5. MARINE MAMMALS
Marine mammals include mustelids (otters), pinnipeds (seals) and cetaceans (whales, dolphins and
porpoises), all of which are vulnerable to the direct effects of oil and gas activities such as noise,
contaminants and oil spills. They are also affected indirectly by any processes that may affect prey
availability.
Mustelids
Only freshwater otters are to be found in European waters, hence routine offshore oil and gas
activities do not directly affect these mammals. However, in cases of extreme oil spills where oil is
washed ashore, the effects could be detrimental to some local populations which occur in estuarine
waters. One such effect is hypothermia, resulting from the otters’ fur being covered in oil and no
longer being able to function as a thermal layer.
Pinnipeds
Seals tend to frequent inshore waters but have been seen from a number of platforms in the North
Sea (Cosgrove, 1996). Both grey seals (Halichoerus grypu) and common seals (Phoca vitulina) have
breeding colonies along the coastline of the UK. Information on the distribution of seals is based
almost entirely on observations at terrestrial haul out sites and although direct observations can be
made at sea, sightings are rare and most observations continue to be made at inshore areas.
Tagging studies on the behaviour and movement of seals at sea have been undertaken. Basic tags
such as flipper tags have revealed that grey seal pups may travel far from their natal sites within their
first few months at sea, being found as far afield as Norway (McConnell et al., 1984). Transmitters
such as VHF (Thompson and Miller 1990; Thompson et al., 1989) and in particular satellite relay tags
(McConnell et al., 1992 and 1999) have revealed that seal movements are on two geographical scales.
Common seals were shown to predominantly spend their time at or near haul out sites, with short
trips to localised offshore areas. They were occasionally found to travel up to 45 km on feeding trips
of up to 6 days, although the duration of most trips was less than 12 hours (Thompson et al., 1990).
Grey seals, on average, spend the majority of their time within a similar range with a trip duration of
less than 3 days, although they occasionally make long‐distance trips of over 100 km (McConnell et
al., 1999). Trips by pups have been reported over large areas, for example from the Isle of May, up
the Norwegian coast and down to the Netherlands (JNCC, 2007). However, the general pattern of
close proximity to haul out sites suggests that these distant trips are uncommon and possibly made by
only a few individuals (Hammond, 2000). Since the area of the development lies approximately 183
km east of the UK coastline, neither grey seals nor common seals are likely to occur in the area.
Cetaceans
Many of the activities associated with the offshore oil and gas industry have the potential to impact
on cetaceans. Factors which could cause disturbance include noise or obstruction. The actual impact
will depend on the scale and type of activity. Activities with the potential to cause disturbance
include drilling, seismic surveys, vessel movements, construction work and decommissioning (JNCC,
2008).
As marine mammals feed on fish and/or plankton, contamination of the water column affecting the
food source could have a negative impact on cetaceans. Direct impacts could occur due to changes in
prey availability or indirectly as a result of bioaccumulation of contaminants. However, as cetaceans
tend to have large feeding grounds, the localised contamination associated with the normal activity of
oil and gas installations is unlikely to have a major impact on individuals.
As with most species, an optimal survey design for monitoring population sizes of cetaceans would
involve surveying the species across its entire distribution at any one time. The impracticality of such
a task, combined with the difficulties of species identification, has made it difficult to confidently
assess cetacean population sizes. The JNCC has compiled an Atlas of Cetacean Distribution in
Northwest European Waters (Reid et al., 2003). This resource provides an indication of types of
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