West Highlands SMR

This section summarises the information from the Marine Protected Areas (MPAs) and intertidal and continental shelf habitats assessments from SMA2020. It also provides information from the relevant case studies relating to Priority Marine Features (PMFs), with a focus on habitats.  Further work is required to enable assessment at a regional scale for most species; this will be included in Scotland’s next marine assessment.

At a SMR/OMR scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018.  For the marine habitats, the focus is on interpreting the relevant intertidal and continental shelf habitat assessments – biogenic habitats, predicted extent of physical disturbance to the seafloor  (BH3) and intertidal seagrass beds.  For PMFs, a summary is provided of the changes in our understanding of the habitats of most relevance to the West Highlands SMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are 30 MPAs in the West Highlands SMR that contribute to the Scottish MPA network (see Table 1).  Some of these MPAs overlap completely or partially in terms of their spatial coverage and/or the features (habitats, species, etc.) they were set up to help conserve.  They are counted as separate MPAs because they have been established under different legislation which influences the way in which they are managed.  Also note that there are MPAs that straddle the boundaries between different SMRs/ OMRs.  Where this is the case, these MPAs have been counted as contributing to the MPA network in all of the SMRs/OMRs in which they are present.  This means that the total number of MPAs in Scotland cannot be calculated through combining the SMR/OMR totals.  Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole.  

Table 1. Numbers of types of MPAs in the West Highlands SMR that contribute to the Scottish MPA network, including number of new MPAs introduced since 2012.

Note that as of December 2020 there were an additional three MPAs designated in this region in addition to those in the table above (Loch Carron MPA designated in 2019 and Sea of the Hebrides and Shiant East Bank MPAs designated in December 2020).

Highlights from the various MPAs include:

Within the West Highlands SMR there are 30 MPAs covering a range of biological and historical features.  Darmouth Historic MPA contains the remains of a wrecked vessel named the Dartmouth, a fifth-rate Royal Navy frigate built in 1655. Dartmouth was dispatched in 1690 to overcome Jacobite clans in the Western Isles and to secure allegiance to William and Mary. Dartmouth broke anchor in Scallastle Bay in a storm and was wrecked on 9 October 1690 on the small island of Eilean Rubha an Ridire, close to the Morvern shore at the southern entrance to the Sound of Mull.  Burrowed mud, flame shell beds, maerl beds and northern feather star aggregations to name but a few, all thrive in the mosaic of sea lochs, bays and near shore island channels within the Wester Ross MPA. This complex landscape is a legacy from the end of the last ice age, when the ice sheet that once covered most of Scotland retreated. The sea bed shows signs of scarring caused by movement of glaciers with linear piles of boulders and cobbles dropped from the ice marking their passage across the continental shelf.  The Small Isles MPA encompasses waters around the islands of Canna and Rum and is home to the only known aggregation of fan mussels in UK waters, which can grow to between 30-48 cm in length and is one of the UK’s most threatened molluscs. 

Progress in managing MPAs

The progress in implementing management for MPAs in the West Highlands SMR is summarised in Table 2.  This includes information on where spatial management measures are in place and where they are under discussion.  It also includes information on the number of MPAs that have been monitored, whether by statutory bodies or through citizen science.

Table 2. Summary of progress in managing Marine Protected Areas in the West Highland SMR. Note that the spatial measures listed in the table are in addition to the protection provided as a result of consideration of activities/developments through licensing and consenting processes. Also, the monitoring of mammals and habitats within SACs has been split out to reflect the different programmes of work.  These figures cannot be added together to provide a total number of SACs in which monitoring took place because of overlaps in coverage.  

Note that Loch Carron Marine Conservation Order was put in place to support the designation of Loch Carron MPA in 2019.  The MCO put in place for Loch Sunart to the Sound of Jura provides benefits for the Dartmouth Historic MPA.

Within the West Highlands SMR there is a Fisheries Order in place that covers various MPAs (Loch Sunart MPA, Sunart SAC, Lochs Duich, Long and Alsh SAC and MPA, and Loch Laxford SAC), and two Marine Conservation Orders that cover Loch Sunart to the Sound of Jura MPA and Wester Ross MPA. The management measures in the MPAs mainly focus on restrictions for demersal mobile gear but there are also static gear restrictions within Loch Teacius (part of the Loch Sunart MPA) due to the sensitivity of the serpulid aggregations. Further management measures are under discussion for Sound of Arisaig SAC, Loch Moidart and Loch Shiel Woods SAC, and Small Isles MPA.

During this assessment period more than half of the MPAs in this SMR have been monitored at least once by the statutory bodies, and some have had multiple visits.  Monitoring has covered seabirds, intertidal and subtidal habitats and mammals.  Ongoing collaboration between NatureScot and Marine Scotland Science has helped to deliver much of the subtidal habitat work.  Seals continue to be monitored by the Sea Mammal Research Unit via a collaboration with NatureScot.

Citizen science monitoring across seven MPAs is carried out through Seasearch surveys which record the presence of protected features, such as flame shell beds, maerl beds and northern feather star aggregations. Additionally, community groups have and continue to contribute towards monitoring the Wester Ross MPA. Seasearch surveys also contribute towards monitoring Loch Laxford SAC and Lochs Duich, Long and Alsh Reefs SAC. Recreational sea anglers play an important role in monitoring the common skate in the Loch Sunart to the Sound of Jura MPA, such as through photograph submission to SkateSpotter. Sightings data of harbour porpoise in the Inner Hebrides and the Minches SAC are recorded by the Hebridean Whale and Dolphin Trust (HWDT) and the Whale and Dolphin Conservation Shorewatch Sightings programme.

Information on MPA boundaries can be viewed in Marine Scotland’s NMPi. To find out more about specific MPAs, please visit NatureScot’s SiteLINK.  Detailed reports on habitat monitoring are referenced in Further reading – seabed habitat monitoring reports.

Intertidal and continental shelf habitats

SMA2020 contains three relevant habitat assessments: intertidal seagrass beds, subtidal biogenic habitats and predicted extent of physical disturbance to the seafloor.  The biogenic habitats assessment considered the status and trend of two marine habitats, namely flame shell beds and serpulid aggregations. The assessment aimed to include maerl beds, horse mussel beds, subtidal seagrass beds and blue mussel beds as well, and although these are all present in the SMR, there were insufficient data for their inclusion.  Modelling work was also carried out to predict the extent of physical disturbance to the seafloor more generally.  Assessment of the status of intertidal seagrass beds could not be carried out in this SMR due to lack of relevant information from WFD monitoring.

Biogenic habitats

For the West Highlands SMR biogenic habitats as a whole, the status category assigned for SMA2020 was ‘Some concerns’ on the basis of recorded reductions in habitat extent of flame shell beds and serpulid aggregations.

Scallop dredging activity in 2017 was found to have caused degradation of flame shell beds in Loch Carron, amounting to approximately 4% of one bed and 8% of another (Moore et al., 2018, see also case study).  The damage recorded ranged from flattening and disaggregation of the byssal turf and stone matrix to the formation of distinct series of parallel dredge tracks or scars with narrow lines of stones and associated biota separated by broader bands of sandy sediment.  The impacted beds represent a small proportion of the total known extent of the habitat in the West Highlands SMR and so the level of complete loss of flame shell habitat was judged to be <1%.

In recent years knowledge of the distribution of the flame shell beds in the SMR has increased significantly, with further SNH and Marine Scotland surveys in 2018 and 2019 resulting in refinement of the habitat coverage in Loch Alsh (O’Dell, Bulgakova, Amos, & Dewey, 2021; Moore, 2020; Shucksmith, Shelmerdine, & Shucksmith, 2021) (Figure 3).  The 2019 surveys (Shucksmith et al., 2021; SNH, unpublished) have also identified several previously unknown beds around Scalpay and north of Applecross in the Inner Sound (Figure 3) and confirmed this SMR from Loch Alsh to Loch Torridon as the most important in the world in terms of the number and extent of flame shell beds.

Comparison with historical records suggests that it is likely that there has been some contraction of a small flame shell bed at Sruth Lagaidh Narrows in Loch Broom prior to 2011 (Moore, Harries, Trigg, Porter, & Lyndon, 2011). Bed extent was assessed in 2010 as 7 ha and a survey of the site in 2017 found no firm evidence for a temporal change in bed extent since 2010, although there was an apparent improvement in habitat condition, in the form of an increase in the thickness and luxuriance of the byssal turf, which overtopped the bound pebbles and shells in 2017, but not in 2010 (Moore, 2019).

There have been three recent records of flame shells in Loch Linnhe and Loch Leven as a result of Seasearch surveys in 2016 – 2019, although the extent of the habitat is unknown and the flame shells are too sparse for the Loch Leven records to be considered examples of the habitat. 

Figure 3.  Temporal pattern of flame shell bed records in the Inner Sound and adjacent waters.

In Loch Teacuis, an arm of Loch Sunart, serpulid reefs were first recorded in 2006 (Mercer, Howson, & Moore, 2007), with a habitat coverage of 20 ha, within which reef coverage was around 4% (Dodd, Baxter, & Hughes, 2009). By 2015 living reefs had become largely extinct, although scattered reef fragments, largely unoccupied by worms, were still present (Kamphausen, 2015). The cause of loss is unknown. The action of storms on reef structures, perhaps exacerbated by the presence of colonising kelp plants, was suggested as a possible factor (Kamphausen, 2015).

A serpulid reef was first reported in upper Loch Ailort during a 2014 Seasearch dive.  Additional records of serpulid aggregations at 11 sites in the same area resulted from an SNH survey in 2017 (Kamphausen et al., 2018; Moore, 2019), which also established a baseline for future condition monitoring.  The sites were distributed within a narrow band (c.5 m wide) along a 1.6 km stretch of coastline, so the total habitat extent is small (<1 ha).  The aggregations were largely poorly developed, averaging 11 cm in height, with occasional examples attaining 26 cm (Kamphausen et al., 2018).

The confidence in the assessment of the status of biogenic reefs in the West Highlands SMR, which is based on a decline in habitat extent, is considered to be low.  For flame shell beds, the refinement of bed boundaries and the identification of new beds has highlighted the poor understanding of the true extent of the habitat in the SMR, although it is clear that localised habitat loss has resulted from fishing activity in Loch Carron.  For serpulid aggregations in the SMR the overall trend in declining habitat extent is likely to be a robust assessment, although the cause of this decline is uncertain.  The comprehensiveness of the overall biogenic habitat assessment is low due to a lack of data to support assessment of temporal trends in most of the subtidal biogenic habitats (i.e. seagrass, maerl, horse mussel and blue mussel beds).

1.1Predicted physical disturbance to the seafloor

To assess physical disturbance to seafloor habitats SMA2020 employed a modelling approach which generates a map of predicted relative disturbance levels from demersal fishing activity on a scale of 0 (zero) to 9 (severe).  The map was produced by the combination of information on the distribution of habitats, the sensitivity of the habitats (and species present to varying degrees) and the fishing pressure from demersal trawling, dredging and seine netting.  Fishing pressure information was derived from Vessel Monitoring System (VMS) data from 2012 - 2016 and was categorised as either surface abrasion (disturbance of surface and upper layers of sediment) or sub-surface abrasion (disturbance to a depth of >3 cm).  The final predicted disturbance index utilises the greater of these two pressure values and for descriptive purposes has been categorised as no disturbance (0), low disturbance (1-4) and high disturbance (5-9).

It should be emphasised that this method does not measure disturbance to seabed habitats but predicts relative levels of disturbance. These relative levels are dependent upon the accuracy of habitat data and sensitivity assessments.  Many of the habitat data are derived from modelling and there is a low level of confidence in its accuracy.  Geographical variation in the accuracy of the sensitivity information employed is likely to be great, being dependent upon the level and quality of information used locally.  A significant limitation of the method is that during the assessment period pressure data were only available for vessels >12 m, which has probably resulted in an underestimation of disturbance for the SMRs.

Predicted habitat disturbance for the West Highlands SMR is amongst the highest for the SMRs, with 65% of the seafloor subject to high disturbance compared to an average of 50% for all SMRs and 8% with no disturbance (average of 12% for all SMRs) (Figure 4).  Disturbance levels in open waters closely mirror the distribution of sub-surface abrasion pressure and mud (outwith long-standing fishery exclusion areas) and are high over much of the area to the south of Skye and to the north of Skye as far as Rubha Rèidh.  The demersal fisheries prohibitions within the relevant MPAs were enacted between 2015 and 2019 and so will have had little effect on the assessment, which covered the period 2012 - 2016.

Figure 4.  Predicted physical disturbance to the seafloor in the West Highlands SMR and prohibition areas for all mobile demersal fishing. (Note that the prediction of physical disturbance covered the period 2012-2016 and so the fisheries prohibition relating to the relevant MPAs will have had little effect on this assessment.) 

Priority Marine Features and birds (non-PMF)

Overview of recorded PMFs and birds

The West Highlands SMR supports a range of PMFs and breeding seabirds as well as wintering waterbirds (i.e. waders, estuarine waterfowl, seaduck and coastal water feeding birds) as detailed in Table 3. 

Table 3: Details of PMFs, seabirds, and wintering waterbirds found in the West Highlands SMR

The West Highlands SMR has 59 PMF habitats and species, and 32 marine bird species. 

Serpulid aggregations, which are dense clumps of white chalky tubes each containing a Serpula vermicularis worm, occur in just a few isolated areas on the west coast of Scotland, including Loch Teacuis (an arm of Loch Sunart) and Loch Ailort.   Northern sea fan communities are restricted to the west coast of Scotland.  The extent of known examples of northern sea fan and sponge communities vary considerably, from isolated patches on mixed coarse sediments surrounded by burrowed mud in the Sound of Canna, through to extensive bedrock plateaus on the Shiant East Bank.  The West Highlands SMR is an important area for basking sharks. They migrate here during the summer and can be seen feeding at the water surface between June and October each year. They gather in large numbers, sometimes hundreds, and may remain within the SMR until late October before many head south for the winter or into deeper water.  The West Highlands SMR is one of the richest in the UK for marine mammals, some of the commonest species are the harbour porpoise, short-beaked common dolphin, white-beaked dolphin, Risso’s dolphin, and minke whale. 

There are also large wintering populations of great northern diver, black-throated diver, red-breasted merganser and Slavonian grebe.

Progress in understanding of intertidal and continental shelf habitats listed as PMFs

Over the last 10 years there has been a change in emphasis of survey work in the SMR, with much of the earlier work by government agencies focused on obtaining an understanding of the distribution and conservation importance of habitats and species through detailed examination of the sea lochs.  Over the 2012 - 2018 assessment period the focus has turned to improving understanding of PMF distribution and to the identification and subsequent monitoring of MPAs, as well as building up a broad understanding of habitat distribution to guide MPA boundary setting and checking that implemented management measures are effective.

The temporal sequence of records of all PMF habitats is provided in Table 4 and illustrated in Figures 5 and 6, based on inclusion in the Marine Recorder (2021) and GeMS (2021) databases, as well as identified additional sources.  Associated commentary, however, is restricted to PMFs for which the information has the potential to inform regional marine planning.  For example, some PMFs are excluded on the basis that they are very widely distributed and for which the records represent a small proportion of their likely distribution, such as several of the kelp habitats.

Table 4 shows that the contribution of citizen science observations has increased from 15% of the total PMF records before 2012 to 25% in more recent years, and the contribution for particular PMFs such as kelp beds, seagrass beds, northern sea fan and sponge communities and low or variable salinity habitats has been particularly important.

Table 4.  Temporal frequency of PMF habitat records within the West Highlands SMR obtained from GeMS (2021), Marine Recorder (2021) and other sources.  The numbers of All records are given, as well as those from Citizen Science (CS) surveys alone.  *3,579 records derived from the analysis of single video frames of serpulid aggregations are excluded.

There has been a large expansion in the number of burrowed mud records since 2011 (Figure 5).  In addition, knowledge of the probable distribution of the habitat is available from annual Nephrops burrow density surveys carried out by Marine Scotland from 2007 - 2016.  While Nephrops is also associated with several other habitat types, these data indicate that burrowed mud is likely to cover the sea bed of a high proportion of the open waters of the SMR.  Recent surveys by SNH, Marine Scotland and SEPA have emphasised its importance also in more coastal areas, including providing a far more detailed picture of the extent of the habitat in several sea lochs, particularly the PMF component biotope SS.SMu.CFiMu.SpnMeg.Fun in Lochs Linnhe, Sunart, Duich, Alsh and Carron, as well as off the south-east and south-west coasts of Skye.   Recent records of the component biotope SS.SMu.CFiMu.MegMax in the region are far fewer, but the habitat was well represented in the Sound of Arisaig in 2014 (Moore et al., 2015) and there are scattered 2018-19 records east of Skye (O’Dell, Bulgakova, Amos, & Dewey, 2021; Shucksmith, Shelmerdine, & Shucksmith, 2021).

There have been significant improvements in the known distribution of several other PMFs in recent years (Figure 6).  Several previously unknown flame shell beds have been identified in the Inner Sound area and in Loch Linnhe since 2017, and the pre-2012 records of serpulid aggregations in Loch Teacuis have been supplemented by observations of another example of the habitat in Loch Ailort in 2014-17. Many additional horse mussel beds have been identified, although most are populated by low densities of mussels, with several so low as to be of questionable validity in terms of identification as a bed. However, abundant mussels have been recorded at new sites in Loch Alsh (Moore et al., 2013) and Loch Carron (Moore et al., 2018).

Records of low or variable salinity habitats since 2011 have mostly served to supplement historical information of the habitat in sea lochs, particularly Lochs Sunart and Duich, but in addition new locations have been identified by Seasearch surveys around the Summer Isles in 2017-19 and in Loch Carron in 2017-18.  Similarly, tide-swept algal community records largely confirm existing known locations, although there are several recent isolated records, particularly in more open waters, as well as the identification of the extensive distribution of the habitat in Strome Narrows in Loch Carron (Moore et al., 2018).

Records of maerl beds have more than doubled since 2011, with extensive new locations identified as a result of SNH and Marine Scotland surveys of the South Skye sea lochs in 2014 and 2016 (Allen, 2018; Moore, 2015) and the Inner Sound and adjacent waters to the south in 2018 and 2019 (O’Dell et al., 2021; Shucksmith et al., 2021).  New locations for the related PMF habitat ‘maerl or coarse shell gravel with burrowing sea cucumbers’ have also recently been recorded in these areas in 2016 (Seasearch, unpublished) and in 2019 (Shucksmith et al., 2021), as have areas of northern sea fan and sponge communities.  The latter has been found during SNH and Marine Scotland surveys to be extensively distributed in Linne Crowlin at the southern end of the Inner Sound in 2019 (Moore, 2020), in the south Skye sea lochs in 2014 and 2016 (Moore, 2015, 2017) and around the Small Isles in 2018 -19 (Moore, 2020; O’Dell et al., 2021). Recent citizen science observations from 2017 - 19 have also confirmed the south Skye sea lochs to be important areas for subtidal seagrass beds.

Figure 5  Temporal pattern of records of selected burrowed mud PMF habitat and species components for the West Highlands SMR, as well as mean Nephrops burrow densities from Marine Scotland monitoring surveys.

Figure 6.  Temporal pattern of records of selected PMF habitats for the West Highlands SMR.

Status and trend in grey and harbour seals

Grey seal pup production at the major breeding sites is monitored biennially and has shown an increasing trend in numbers and their status is assessed as ‘few or no concerns’.  Harbour seal numbers are monitored on a rolling 4/5year cycle and have shown little or no change over the assessment period and their status is assessed as ‘few or no concerns’.