Braemar Pockmarks Site of Community Importance Fisheries Measures
Introduction
The Braemar pockmarks were submitted to the European Commission as a possible
SAC in August 2008 and approved by the commission as a Site of Community
importance on 22 December 2009. Member States have a maximum of 6 years from
the site being adopted as a SCI to implement the necessary management measures
and formally designate the site as a SAC.
Under Article 6 of the Directive, Member States have a duty to take appropriate
steps to avoid the deterioration of natural habitats for which SACs have been
designated. Commercial fishing has been identified as an activity which could
adversely impact the integrity of the site’s features and as such requires to be
assessed and, if necessary, managed to reduce its impact.
The Commission has issued guidance on a consistent approach to requests for
fisheries management measures under the Common Fisheries Policy. Accordingly,
this document provides the scientific and technical information required to support a
request to the Commission for fisheries regulation under the CFP.
1.
Comprehensive description of the natural features including distribution
within the site.
Braemar pockmarks Site of Community Importance (SCI) is located in the Northern
North Sea Regional Sea (JNCC, 2004; Defra 2004), approximately 240 km east of
the Orkney Islands. The presence of pockmarks in this area is particularly of note as
it occurs outside the region identified by British Geological Survey (BGS) of known
pockmark occurrence in the North Sea (Johnston et al., 2002).
The pockmarks at the site are shallow, ovoid, seabed depressions, probably formed
by venting of biogenic/petrogenic fluids or gases into the water column (Hovland &
Judd, 2009). They cover a range of sizes from those with diameters between 5 and
10 m and a maximum depth of 0.5 m; to larger, less prevalent pockmarks with
diameters between 50 m and 130 m and a maximum depth of approximately 5 m
(Hartley, 2005). Water depth at the site is approximately 120 m.
The Annex I habitat ‘Submarine structures made by leaking gases’ is present at the
site, most recently verified through video and still image data and the presence of
methane derived authigenic carbonate (MDAC) in a number of grab samples, see
Figure 1 (Rance et al., 2013). MDAC pavement slabs, large blocks and smaller
fragments have formed through a process of precipitation during the oxidation of
methane gas. Sidescan sonar also provided evidence of gas bubbles in the water
column, which appeared to be venting from one of the pockmarks, while white
patches on the sediment surface, presumed to be chemosynthetic bacterial mats,
were observed in some video and still images, suggesting that methane seeps within
the site are currently active (Rance et al., 2013). The presence of shell hash within
pockmarks suggests continuing periodic expulsion of fluid or gas resulting in a
winnowing away of finer sediments (Hartley, 2005; Rance et al., 2013).
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Exposed carbonate structures provide a habitat for marine fauna usually associated
with rocky reef, as well as highly specific chemosynthetic organisms which feed off
both methane (seeping from beneath the seafloor) and its by-product, hydrogen
sulphide (Judd, 2001). Larger blocks of exposed carbonate also provide shelter for
fish species such as wolf-fish, cod, haddock and conger eel.
Figure 1: Braemar Pockmarks SCI site map
2.
Scientific rationale for the site's selection in accordance with the
information provided in the Natura 2000 data form. Intrinsic value of its
features. Specific conservation objectives.
The information provided in this section corresponds to that submitted to the
Commission in 2008. In some cases, more recent survey information has become
available since submission and, where relevant, this is noted in the text. The new
survey information has not been fully evaluated to determine its potential influence
on our assessment of representativity, area or conservation of structure and function
of the features but it is not currently considered likely it will result in any change to
the assessment.
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2.1 Representativity
The Braemar pockmarks site is located in the Northern North Sea Regional Sea and
represents a range of different sizes and forms of Annex I “Submarine structures
made by leaking gases” in this area. The faunal communities are representative of
those present on submarine structures made by leaking gases, consisting of
organisms dependent on chemosynthesis as well as anemones and hydroids
(Hartley, 2005) therefore the grade for the feature is B: good representativity.
2.2 Area of habitat
An evaluation of the area of the site covered by submarine structures made by
leaking gases in relation to the total area covered by this interest feature in UK
waters is not possible, since all occurrences of this habitat are not known. It is likely
that the Annex I habitat at the Braemar pockmarks site comprises between 15 and
100% of the total extent of submarine structures made by leaking gases; therefore
the grade for this criterion is A.
2.3 Conservation of structure and functions
Degree of conservation of structure
VMS data (2005-2012) suggests that this area is likely to be subject to demersal
fishing activities and the biological and physical structure of the interest feature at the
Braemar pockmarks site are thought to have been partially impacted by bottom
trawling (John Hartley, pers. comm., 2005). Trawl marks in sidescan sonar and
multibeam back scatter data were also observed, often overlapping the feature
during surveys in 2012 (Rance et al., 2013), see Section 4 for further detail. It is
possible that demersal trawling has dispersed and fragmented some of the feature
through direct impact, may have indirectly contributed to the burial of some of the
carbonate formations through mobilisation of sediment and may also have modified
the structure of the encircling pockmarks (John Hartley, pers. comm., 2005).
However, much of the feature is still intact.
Degree of conservation of functions
The prospects of this feature in terms of maintaining its structure in the future (taking
into account unfavourable influences and reasonable conservation effort) are good.
Regulations are in place to regulate oil and gas activity in and around SACs in the
UK Continental Shelf Designated Area, and fisheries management, where required,
will be realised through the Common Fisheries Policy. The laying of submarine
cables and pipelines would also require regulatory consent at this site. The feature is
distant from terrestrial sources of pollution.
Restoration possibilities
Restoration methods in the offshore area focus on the removal of impacts, which
should allow recovery where the habitat has not been removed. Restoration of the
biological communities at the Braemar pockmarks site may be possible where the
submarine structures have not been destroyed.
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However, where damage has occurred, the restoration potential is unknown. MDAC
of the kind found at the site is accreted naturally over long time periods, and further
accretion is dependent upon sufficient gas seepage and the presence of specific
chemosynthetic micro-organisms. Anecdotal evidence suggests that the submarine
structures are sustained by shallow biogenic gas seepage (John Hartley, pers.
comm., 2005); however, if this is not the case and the structures are supported by
deeper petrogenic gas, there is potential for a reduction in seepage if the underlying
reservoir is depleted through commercial activities (Oil and Gas UK, 2008).
3.
Basis for the spatial extent of the site boundary clearly justified in terms of
conservation objectives.
The proposed boundary for the Braemar pockmarks site has been defined using
JNCC’s marine SAC boundary definition guidelines (JNCC, 2012) and information
provided during public consultation on this site in 2007-2008. The proposed
boundary is a simple polygon enclosing the minimum area necessary to ensure
protection of the Annex I habitat. Coordinate points have been located as close to
the edge of the interest feature as possible, rather than being located at the nearest
whole degree or minute point.
As bottom trawling may pose a significant threat to the interest feature, the proposed
boundary includes a margin to ensure its protection. To account for the potential
presence of submarine structures within the pockmark depressions, an exclusion
zone was estimated as the maximum distance between the centre of the largest
pockmark to the pockmark edge (i.e. 65 m).
Additionally, to avoid accidental incursion of gear into the site, a buffer zone based
on fishing warp length to depth ratio was added. The maximum depth of water
around the feature is 125 m; therefore, assuming a ratio of 3:1, the proposed
boundary is defined to include a margin of 375 m. Thus a total buffer zone of 440 m
from the centre of the pockmark depressions was proposed.
The location of the Annex I habitat is drawn from data provided by a 2012 survey of
the site (Rance et al., 2013), see Figure 1. The presence of submarine structures
made by leaking gases was confirmed using a remotely operated vehicle (ROV;
2005 survey), camera sledge and grab samples.
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4.
Threats to the long-term natural distribution, structure and functions of the
habitats and the long-term survival of associated species from different
types of fishing gear. List of other human activities in the area that could
damage the habitats.
4.1 All demersal towed gears (including scallop dredges, beam trawls and
otter trawl)
Direct evidence of impacts of towed gears to submarine structures made by leaking
gasses is limited. However, the biological communities that develop on exposed
structures typically include many of the same species that can be found on subtidal
rocky habitats in similar environmental conditions and it is likely that the effects of
fishing will be similar.
Demersal towed gears have the potential to effect the natural distribution of the
features through physical removal of carbonate structures by dragging bottom-fishing
gear over the seabed (Sewell and Hiscock, 2005). Demersal trawling at the site may
result in dispersal, fragmentation and possibly burial of some carbonate formations.
The use of towed fishing gears is likely to cause damage or death of fragile, erect
species, such as sponges and corals (Løkkeborg 2005, Freese et al. 1999). Other
species such as hydroids, anenomes, bryozoans, tunicates and echinoderms are
vulnerable to mobile fishing gear (McConnaughey et al 2000, Sewell and Hiscock
2005). Recovery is likely to be slow (Foden et al. 2010). Where fragile, slow growing
species occur, even low levels of fishing have the potential to change the structure
and function of the habitats and may result in the loss of some characteristic species.
There is evidence of trawl scars within the site (Rance et al., 2013), see Figure 2.
Towed dredges may reduce surface complexity by modifying and homogenising the
substrate, as soft rocks may be broken up (Attrill et al., 2011), rolling/moving
boulders (Hall-Spencer & Moore, 2000) and reducing habitat complexity.
5
Figure 2: Locations of trawl scars observed during Cefas survey in 2012
4.2 All demersal static gears (including gillnets, trammel nets, longlines, pots
and traps)
There is no direct evidence from which to determine impacts of static gears on
submarine structures made by leaking gases. However, the biological communities
that develop on exposed structures typically include many of the same species that
can be found on subtidal rocky habitats in similar environmental conditions and it is
likely that the effects of fishing will be similar.
Intensity of static gear fishing in this site is very low and it is considered unlikely that
this activity currently poses a significant risk to the long-term natural distribution,
structure and functions of the habitats or the long-term survival of associated
species. If fishing intensity were to increase to higher levels in the future, there is a
risk of significant impact.
Mechanical impacts of static gear (e.g. weights and anchors hitting the seabed,
hauling gear over seabed, rubbing/entangling effect of ropes) can damage some
species (Eno et al., 1996). Other species appear to be resilient to individual fishing
operations but the effects of high fishing intensity are unknown (Eno et al., 2001).
Recover may be slow, resulting in significant reduction or even loss of characteristic
species (Foden et al., 2010). The individual impact of a single fishing operation may
be slight but cumulative damage may be significant (Eno et al., 2001; Foden et al,.
2010). Sensitivity to low intensity potting is considered low (Hall et al., 2008).
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4.3 Other human activities
The information within this section represents current knowledge of the nature and
extent of activities taking place within or close to the site.
The SAC covers a large proportion of the Braemar gas reservoir and there is one
completed exploration wellhead within the site. There is a requirement to carry out
routine inspections, and preventative and remedial maintenance on the well and subsea infrastructure. Routine activities include the locating of a drilling rig to gain
access to the wellhead for maintenance activity. Any future construction on site could
lead to removal of the feature, and permanent infrastructure may prevent its natural
recovery. Additionally, as the feature lies in a low energy environment, drill cuttings
may not be removed by currents. The feature’s associated biological community is
located in a low-energy environment and unlikely to be accustomed to changing
sediment levels. Whilst an increase in suspended particulates may benefit filter
feeders, many species are adversely affected by smothering (Hartnoll, 1998).If
MDAC is covered, there will be a loss of hard substrate habitat for many associated
species.
TAT14 telecommunication cables run west to east across the site, overlaying
approximately 1 km of the area. Permanent infrastructure, (including oil, gas and
telecommunications infrastructure) may prevent natural recovery of the feature;
however, coverage of the feature by the cable is relatively low.
MDAC is accreted naturally over long time periods and further accretion may be
dependent upon sufficient gas seepage as well as the presence of specific chemosynthetic micro-organisms. If the structures are supported by deeper petrogenic gas,
there is the potential for a reduction in seepage and subsequent accretion of MDAC
if the supply of methane is interrupted, e.g. by drilling. There is a gas condensate
production facility consisting of an export pipeline from a wellhead 90m from the
southern boundary of the site, and a platform approximately 12 km to the east.
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5.
Fleet activity in the area and in the region, distribution of fleets (by nation,
gear and species), and information on target and by-catch species, all over
the last 3 years
The following is a summary of the fishing activity associated with the Braemar
Pockmarks Site of Community Importance. The majority of the information is derived
from VMS data, either aggregated into effort grids over four years (2006-2009), in
raw “ping” format, indicating the presence of UK vessels over five years (2007-2011)
or non UK vessels over three years (2009-2012). We also present UK landings
statistics over the same time period. There is unlikely to be any <15 m vessel activity
in Braemar Pockmarks site. The available evidence in the area suggests that mobile
fishing activity overlapping the site is principally limited to demersal otter trawling and
Scottish seine netting with limited evidence of static gear activity.
Otter trawling
The greater Fladen Ground region is an area of major importance to the Scottish
demersal fleet and the Braemar Pockmarks SCI lies to the east of this area. Effort
greater than 1000 hours (in a 0.05 x 0.05 degree cell) over a four year period is
typical for much of the Fladen Ground area, however effort in the region overlapping
the site is typically lower (effort ranges from 245- 483 hrs across the site between
2006 to 2009; Figure 3). There does not appear to be a clear pattern in the
distribution of activity across the site as a whole. The majority of landings from UK
vessels fishing in ICES rectangle 46F1 land into Peterhead, although with landings
also recorded for other north east Scottish ports. The nephrops fishery in the area
was the highest value over the period 2006-2011 although with significant whitefish
landings also recorded.
Figure 3: UK demersal trawl activity at Braemar Pockmark SCI 2006-2011.
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The non-UK demersal fishery overlapping the Braemar Pockmark SCI (maximum
effort 203 hrs effort in any grid during 2006 to 2009; Fig X) is primarily prosecuted by
the Danish trawl fleet. The ping data (2009-2012) suggests that there has been a
reduction in effort over the last number of years.
Figure 4: non-UK demersal trawl activity at Braemar Pockmarks SCI 2006-2009.
Note: Due to the small number of vessels operating in the area 2009-2012, it was not
considered appropriate to publish VMS ping data in the current map.
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Seine Netting
The seine net fishery in the Braemar Pockmark area is very low intensity (<7hrs
effort over 4 years 2006-2009). It is likely that the fishery in this area is typical of
seine net activity across the Fladen Ground area, i.e. a mixed demersal fishery that
predominantly targets whitefish (haddock, cod and whiting) but with significant
landings of monkfish and several flat fish species (see Figure 5).
Figure 5: Scottish seine net activity at Braemar Pockmarks SCI 2006-2009.
Note: Due to the small number of vessels operating in the area, it was not
considered appropriate to publish VMS ping data in the current map.
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Set Netting
There was evidence of low intensity over-15 m Danish set netting overlapping the
Braemar Pockmarks SCI between 2006 and 2009 (maximum effort of 30 hours in a
single grid over four years), however, there has not been any evidence of activity
since 2009. In addition, it is unclear whether the activity recorded was real or was
due to a gear class misidentification from the EU vessel register. As a result,
discussion with stakeholders will be required to validate the data. See Figure 6.
Figure 6: non-UK netting activity at Braemar Pockmarks SCI 2006-2009.
Note: No VMS ping data exists for 2009-2012.
6.
Seasonal trends in fisheries over the last 3 years.
Due to the relatively low fishing effort in the area no seasonal trends have been
identified.
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7.
Proposed fisheries management measures to maintain the habitats
features in favourable condition. Are they proportionate and enforceable?
Other conservation measures that apply to the area.
The conservation objective for the Braemar Pockmarks SAC is to restore the Annex I
habitat Submarine structures made by leaking gases to ‘Favourable Condition’, such
that:



The natural environmental quality is restored;
The natural environmental processes are maintained;
The extent, physical structure, diversity, community structure and typical
species representative of the submarine structures made by leaking gases in
the Northern North Sea are restored.
Having consulted with representatives of all fishing fleets active in the area (Scottish
and Danish) JNCC have advised that the following management measures will be
required in order to achieve these conservation objectives;

Prohibition of fishing with bottom contacting gears (scallop dredges, beam
trawls, otter trawls and seine nets) throughout the area of the SAC. The site
boundary already includes a buffer zone around the known features equal to
three times the water depth and no further buffer zone will be required.

No additional restriction on pelagic gears.

At present, no additional restriction on static gears (pots, gillnets and longlines
are not currently used in the site) but if, in the future, there is evidence to
suggest that increasing levels of static gears are having an impact on the
features, some restriction may be considered necessary.
Total value of landings from the site by UK vessels between 2010 and 2012 is
estimated at £9,900 for 3.3 days of effort. The site represents a very small proportion
of the area over which the fisheries operate and it is therefore likely that reduced
catches will be partially compensated for by fishing elsewhere.
Other management options considered included “no additional management” and
“measures to reduce/limit pressure”. Both these options were considered to pose a
significant risk to the achievement of conservation objectives. The proposed
management objectives are therefore considered to be proportionate.
The measures would be enforceable utilising Vessel Monitoring System, aerial
surveillance, and ship surveillance. Given the extremely low value of fisheries to the
industry a high level of compliance is anticipated.
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8.
Control measures envisaged by the Member State, possible ecological and
control buffer zones to ensure site protection and/or effective control and
monitoring measures.
That all demersal fishing be prohibited with the area formed by these co-ordinates;
1. 58 28.383N 001 26.25E
2. 59 00.383N 001 30.2E
3. 59 00.067N 001 30.95E
4. 58 58N
001 27E
9.
Measures to monitor and assess the maintenance and/or recovery of the
features within the site.
[Text to be added when agreed with JNCC monitoring and assessment teams]
10. Coordination with neighbouring Member States as appropriate.
The intention to make this proposal was discussed with Scottish and Danish
fishermen at a fisheries workshop in Aberdeen in June 2013. Add NS RAC
discussions after demersal working group.
11. Evaluation of possible displacement of fishing effort and impact on new
areas.
With the average annual UK trawl effort estimated at just over 1 day for the entire
fleet combined it is anticipated that the displacement effect of this will be
insignificant.
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