Clyde 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 regional 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 SMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are 12 MPAs in the Clyde 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 Clyde SMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.

There are 12 MPAs in the Clyde SMR that have been designated for a broad range of features including intertidal and subtidal habitats and species, fronts, wintering waterbirds, and breeding seabirds.

There are three Nature Conservation MPAs in the Clyde SMR. The South Arran MPA includes features such as burrowed mud, kelp and seaweed communities on sublittoral sediments, maerl beds, maerl or coarse shell gravel with burrowing sea cucumbers, ocean quahog aggregations, seagrass beds and shallow tide-swept coarse sands with burrowing bivalves. The Upper Loch Fyne and Loch Goil MPA contains burrowed mud, including in Loch Shira, an arm of upper Loch Fyne that supports the densest known colonies of fireworks anemones (Pachycerianthus multiplicatus) in Scotland, and flame shell beds, horse mussel beds, sublittoral mud and specific mixed sediment and ocean quahog aggregations. The Clyde Sea Sill MPA is designated for the thermal front that concentrates nutrients and plankton creating feeding hotspots for fish which in turn attract other higher marine predators, such as black guillemot. The sill is of great importance to local fish stocks with existing fisheries management measures in place here for spawning cod.  In addition, the various sedimentary habitats within these sites also contain significant carbon stores (i.e. blue carbon)

There are two SPAs within the Clyde SMR. The cliffs of Ailsa Craig support nesting populations of seabirds of European importance including one of the largest northern gannet colonies in the world as well as lesser black-backed gulls, common guillemot and black-legged kittiwakes. The Inner Clyde SPA supports a variety of migratory wintering waterbirds, in particular common redshank, which feed on the eelgrass, mussel beds and on the many invertebrates, such as worms and snails, living within the mudflats and saltmarsh.

Progress in managing MPAs

The progress in implementing management for MPAs in the Clyde 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 Clyde 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 birds and habitats within SSSIs has been split out to reflect the different programmes of work.  These figures cannot be added together to provide a total number of SSSIs in which monitoring took place because of overlaps in coverage.  

During this assessment period, an Inshore Fishing Order was put in place for Upper Loch Fyne and Loch Goil MPA and a Marine Conservation Order (MCO) for South Arran MPA. The MCO for South Arran MPA includes the Lamlash Bay No Take Zone which has been in place since 2008. The management measures for fishing activity in MPAs within the Clyde SMR mainly focus on restrictions relating to the use of demersal mobile gear. However, there are also static gear restrictions within South Arran MPA for the maerl beds because of their ‘recover’ conservation objective. Further measures are under discussion for Clyde Sea Sill MPA.

During this assessment period the majority of the MPAs have been monitored at least once by the statutory bodies, and some have had multiple visits.  Monitoring has covered seabirds, wintering waterbirds, and intertidal and subtidal habitats.  NatureScot has led on monitoring most of these MPAs, with input from Marine Scotland Science in South Arran MPA.  Seabird monitoring at Ailsa Craig is carried out through a partnership between NatureScot and the Royal Society for the Protection of Birds. 

Citizen science has contributed towards monitoring the South Arran MPA and Upper Loch Fyne and Loch Goil MPA. Numerous Seasearch surveys have taken place in both MPAs providing data on the presence of benthic habitats and species, such as fireworks anemone. The Community of Arran Seabed Trust (COAST), in partnership with universities, has carried out work including monitoring biodiversity and habitat quality in the Lamlash Bay No Take Zone and South Arran MPA. The Inner Clyde SSSI and Ramsar site are monitored through the British Trust for Ornithology’s Wetland Bird Survey citizen science project.

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; biogenic habitats; and predicted extent of physical disturbance to seafloor.  The assessments consider the status and trend of six marine habitats within this SMR, comprising intertidal seagrass and the following subtidal biogenic habitats: blue mussel beds, horse mussel beds, seagrass beds, flame shell beds and maerl beds.  Modelling work was carried out as part of the assessment to predict the extent of physical disturbance to the seafloor more generally.

Intertidal seagrass

Single baseline surveys of seagrass beds were carried out on four beds at two locations (outer Clyde estuary and Hunterston) in 2016 but as the status assessment methodology (Water Framework Directive seagrass tool - WFD-UKTAG, 2014) is dependent upon the analysis of a temporal series of data, no indication of status for the region, nor trend, could be derived for the period 2012 - 2018.  These beds form part of an ongoing Water Framework Directive monitoring programme that will enable status assessments to be undertaken in future years. 

Subtidal biogenic habitats

For the Clyde 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 and maerl beds. 

The only flame shell bed to have been examined in the Clyde SMR during the SMA2020 assessment period is that at Otter Spit in Loch Fyne (Moore et al., 2013). This was thought to possibly represent the only remaining bed in the Clyde SMR, although a small bed of around 1 ha. was discovered off the south of Arran in 2020 (COAST, 2020).  In 2012 the extent of the Otter Spit bed was estimated to be 50 ha (Moore et al., 2013).

Knowledge of the status of the Otter Spit bed has been enhanced by the establishment of a monitoring programme, for which a baseline survey was carried out by SNH in 2015.  Elements of this have been published (Allen, 2017 - for infaunal data,  Moore, 2019 - for dropdown video).  The monitoring programme incorporates the establishment of permanent monitoring transects, which will facilitate future identification of trends in the status of the bed; however, despite the use of different methodologies some analysis of change over the period 2012 – 2015 is possible.  There is a recorded change in bed extent from an estimated 50 ha in 2012 to 59 ha in 2015 (Figure 3) but as the recorded extension of the bed boundary was in areas that were not sampled by the 2012 survey, this is not evidence of real temporal change.  In terms of bed condition there was no clear temporal pattern in the percentage cover of the seabed by the flame shell byssal turf (Figure 3).  A comparison of the taxon richness of the faunal community associated with the habitat, derived from replicate core samples taken at one station in 2012 and at three stations in 2015 (in areas where flame shells were present in the cores) revealed a decrease in mean species richness per core from 57 in 2012 to 32 in 2015.  However, the reduction was only significant between the 2012 station and one of the 2015 stations (ANOVA with Tukey multiple comparison test, P = 0.042) and is not conclusive.  Possible explanations for the difference include the coarser sieve mesh used in the later survey (1.0 mm rather than 0.5 mm) and the low densities of flame shells at the 2015 station. 

Figure 3.  Flame shell turf cover, abundance records and estimates of bed distribution from surveys in 2012 and 2015 at Otter Spit, Loch Fyne.

In addition to the flame shell bed there are also historical records of a 17.5 ha maerl bed at Otter Spit, last recorded in 1999 (Hall-Spencer & Moore, 2000b).  This was found to have disappeared by 2012 (Moore et al., 2013), representing around a 10% reduction in the known extent of the habitat in the Clyde SMR.  The data indicate a decreasing trend in maerl bed status between 1999 and 2012.  While this is no doubt true for the Otter Spit maerl bed, the confidence in extending this conclusion to the Clyde SMR as a whole is low, for the same reasons as those listed above for the flame shell habitat.  As in the case of flame shell beds, scallop dredging has been implicated as a significant contributor to the decline of maerl beds in the Clyde SMR (Hall-Spencer & Moore, 2020b).

A 2018 video survey programme has resulted in a considerable expansion in the distribution of Clyde SMR maerl bed records (O’Dell et al., 2021) (Figure 4) although the analysis was not completed in time for inclusion in the SMA2020 assessment.  The results highlight the poor condition of maerl habitats in the SMR.  A total of 87 new records were generated, most of these ‘maerl bed’ records represent locations where no living maerl was found (50).  Only sparse live maerl thalli were found at a further 32 sites. The remaining five were located within or adjacent to known maerl beds off Pladda Island, within the South Arran MPA.  These results in combination with those obtained from re-analysis of dropdown video footage from a 2015 SNH survey (Moore, 2021) increases the estimated extent of the Pladda beds from 32 ha to 49 ha.

Unattached Phymatolithon calcareum maerl thalli in Scottish waters (the dominant species) are probably almost entirely vegetatively propagated (Birkett et al., 1998).  With growth rates of the order of 1 mm yr^-1 this indicates that recovery of damaged beds is likely to take decades, and significantly longer in the absence of live maerl material. 

Although present in the SMR, the data for subtidal seagrass, blue and horse mussel beds were insufficient to derive assessments of status for SMA2020.  Although habitat extent data are available for some of the subtidal seagrass beds south east and south of Arran, no temporal data have been collected.  There are no data on the extent of the subtidal blue mussel bed habitat in the Clyde SMR.  Beds have been recorded at three locations between 2012 and 2018 in upper Loch Long and Loch Goil (Figure 5) with records of abundant mussels at two of them.  There are also no estimates of horse mussel bed extent in the region, although the habitat has been recorded at 18 locations (Figure 5).  At six of these locations the abundance of horse mussels, is low (<1/m² or <Common on the SACFOR semi-quantitative scale) and therefore these are not considered to be beds.

Figure 4.  Temporal pattern of maerl bed records in the Clyde SMR.

Note that the majority of maerl records in this region contain no living maerl. A substantial proportion contain only sparse live maerl thalli.

Figure 5.  Distribution of subtidal horse and blue mussel bed records in the Clyde SMR with mussel abundance.

Predicted 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.  A lot of the habitat data are derived from modelling and have a low level of confidence in their 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 Clyde SMR is amongst the highest, with 65% of the sea floor 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 6).  Disturbance levels closely mirror the distribution of habitat and species sensitivities to sub-surface abrasion and are high throughout most of the Firth of Clyde, particularly in areas of mud in the southern half of the Firth.  There is a marked reduction in predicted disturbance on the harder, sandier grounds at the mouth of the Firth.  Most of the area now encompassed by the South Arran MPA displayed high levels of disturbance.  The corresponding demersal fisheries prohibition within the MPA was enacted in 2016 and so will have had little effect on the assessment, which covered the period 2012 - 2016.