Orkney Islands 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 the SMR 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 Orkney Islands SMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are 23 MPAs in the Orkney Islands 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 and 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 Orkney Islands SMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.

Highlights from the various MPAs include:

The MPAs in the Orkney Islands SMR cover a wide range of natural heritage features including birds, marine mammals, fish, benthic and intertidal habitats, and geomorphological features. North-west Orkney MPA is an important export ground for sandeels which are a critical component of many North Sea food webs. The MPA plays an important role in supporting wider populations of sandeels in Scottish waters. Specifically, newly hatched sandeel larvae from this region are exported by currents to sandeel grounds around Shetland and the Moray Firth.  The MPA also includes geomorphological features representative of the Fair Isle Strait Marine Process Bedforms such as sediment wave fields, sand wave fields and sandbanks. The Wyre and Rousay Sounds MPA was designated for its seabed habitats and geomorphology. Strong tides are squeezed between the islands of Rousay, Wyre and Egilsay creating the perfect conditions for maerl beds and seaweed communities to thrive on the sandy seabed.  Loch of Stennes SAC is the largest brackish lagoon in the UK and is of particular importance on account of its large size, stability, reduced salinity regime and northern location. The salinity gradient within the lagoon supports a range of communities representing sheltered marine, brackish and freshwater conditions.  There are two SACs designated for their seal interest, Faray and Holm of Faray SAC is an important grey seal breeding site, and Sanday SAC for its harbour seal population which has shown a considerable decline in recent years.  There are a large number of internationally important breeding and wintering marine bird SPAs in the Orkney Islands SMR.  Sule Skerry and Sule Stack SPA are two small and remote islands which lie to the west of the Orkney islands.  These islands support large numbers of seabirds, such as northern gannet, common guillemot, Atlantic puffin, European shag, Leach’s petrel and storm petrel, which forage in the waters off the north coast of Scotland.           

Progress in managing MPAs

The progress in implementing management for MPAs in the Orkney Islands 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 Orkney Islands 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, mammals 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.  

Within the Orkney Islands SMR there is a fisheries order in place for Wyre and Rousay Sounds MPA and Sanday SAC. The management measures for fishing in this region focus on restrictions to demersal mobile gear.  Further management measures for Papa Westray MPA are under discussion.

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 mainly focused on seabirds, wintering waterbirds, and mammals.  Birds have been monitored in a range of different ways, including via a partnership agreement with the RSPB.  As per other SMRs, most of the seal monitoring is undertaken via a partnership agreement between the Sea Mammal Research Unit and NatureScot.

Greater scaup and goldeneye are monitored through Wetland Bird Surveys by the British Trust for Ornithology in the Lochs of Harray and Stenness SSSI.

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 seafloor.  Assessment of the status of subtidal biogenic habitats is based on temporal reductions in extent of six habitat types: seagrass beds, serpulid aggregations, flame shell beds, maerl beds and horse and blue mussel beds.  Although beds of subtidal seagrass, flame shells, maerl and horse mussels have been recorded within the region, no data are available on temporal changes in extent of these habitats and hence no status assessments could be made.  There are no records of serpulid aggregations or blue mussel beds.  Likewise, intertidal seagrass beds have not been recorded as part of WFD work in the region, and so no analysis could be carried out.  Modelling work was completed as part of the assessment to predict the extent of physical disturbance to the seafloor more generally.

Much progress has been made since 2018 in our understanding of the distribution of flame shell, horse mussel, maerl and subtidal seagrass beds in the region and these are outlined in the section on progress in our understanding of PMF habitats.

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.  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 by mobile demersal fishing for the Orkney Islands SMR is slightly lower than the average for SMRs in terms of the proportion of the seabed, with 41% high disturbance compared to the average of 50% for all SMRs (Figure 3).  Ten per cent of the seabed is predicted to experience no disturbance (average of 12% for all SMRs).  The Orkney Islands are surrounded by predominantly sandy and coarse sediment habitats and the disturbance levels closely correspond to the degree of surface abrasion.  Higher disturbance levels are patchily distributed within the region.  The demersal fisheries prohibition within the MPAs came into force in 2016 and so will have had little effect on the assessment, which covered the period 2012 - 2016.

Figure 3.  Predicted physical disturbance to the seafloor in the Orkney Islands 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 Orkney Islands 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 Orkney Islands SMR

There are 45 PMF habitats and species and 36 marine bird species in the Orkney Islands SMR.  Whilst flame shell beds are mainly distributed on the west coast of Scotland they have also been recorded in the Orkney Islands SMR.  In the nearshore waters there are numerous maerl beds extending over many square kilometres.  As well as supporting diverse marine life underwater, dead maerl from these beds helps supply the sandy beaches around Orkney.

There are important spawning grounds for herring and important nursery grounds for sandeels which are an important prey species for both commercial fish species such as cod, haddock and whiting and also an essential food source for breeding seabirds and mammals.

Six cetacean species occur regularly in the Orkney Islands SMR, namely harbour porpoise, minke whale, white-beaked dolphin, Risso’s dolphin, killer whale, and bottlenose dolphin with a further four species that normally inhabit more offshore waters as casual visitors: short-beaked common dolphin, Atlantic white-sided dolphin, long-finned pilot whale and sperm whale. Together with otters and harbour and grey seals it supports one of the highest numbers of PMF mammal species of any SMR/OMR, making it one of richest areas in the UK.

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, although latterly survey effort became increasingly associated with the establishment and monitoring of the Sanday SAC and East Sanday Coast SSSI.  Over the 2012 - 2018 assessment period the focus turned to improving understanding of PMF distribution.

The temporal sequence of records of all PMF habitats is provided in Table 4, 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.  Temporal frequency of PMF habitat records within the Orkney Islands 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.

Table 4 shows that the proportion of citizen science records has risen from a pre-2012 level of 9% to 35% in later years, with major contributions to our understanding of the distribution of flame shell, horse mussel, maerl and seagrass beds, as well as tide-swept algal communities.

Following the first identification of an Orkney Islands SMR flame shell bed in Scapa Flow in 2013 by Seasearch divers and further Seasearch records of the habitat in 2015 - 2018, knowledge of the extent and distributional pattern of the bed was considerably enhanced in 2019 by an SNH diving survey (Kamphausen, 2019) and a Marine Scotland/SNH drop-down video survey (Shucksmith, Shelmerdine, & Shucksmith, 2021) (Figure 4).  The records lie within an area occupying 508 ha (GeMS, 2021).  However, the habitat is not continuous within this area, and the recorded density is such that no quantitative estimate of the habitat extent can currently be made.  While there are areas of high coverage of the seabed by the flame shell byssal turf, overall the coverage appears lower than some of the major beds in the West Highlands SMR.

Figure 4.  Flame shell bed distribution in Scapa Flow, Orkney Islands, with supporting habitat records from 2019 showing byssal turf cover, and earlier Seasearch records showing flame shell abundance based on the semi-quantitative SACFOR scale.

Figure 5.  Temporal pattern of records of selected PMF habitats for the Orkney Islands SMR.

There has also been a great improvement in understanding of the distribution and condition of horse mussel beds in the Orkney Islands SMR in recent years, with the great majority of records dating from 2012 – 2019.  This has included the mapping of a 71 ha bed in Scapa Flow following surveys by Seasearch (2011 – 2013) and SNH/Marine Scotland (Sanderson et al., 2014; Shucksmith et al., 2021), the identification of the habitat within and adjacent to the Scapa Flow flame shell bed (2012 – 2014 Seasearch surveys; Kamphausen, 2019; Sanderson et al., 2014) and the identification of a previously unknown bed in Stronsay Firth in 2013 (Moore, 2014) (Figure 5).

Prior to 2012 there were scattered records of low or variable salinity habitats within the SMR, but mostly located around Sanday.  Seasearch surveys from 2013 - 2017 have indicated that the habitat is more widespread in Scapa Flow than previously recognised.

As a result of pre-2012 survey work, extensive areas of maerl have been identified around Graemsay, Shapinsay, south-west of Sanday and east and south of Rousay (the Wyre and Rousay Sounds MPA).   Seasearch surveys from 2014 – 2018 added distributional detail at these locations, and a 2019 Marine Scotland survey (Shucksmith et al., 2021) provided a major advance in terms of filling gaps in distributional knowledge in these areas and the identification of a previously unknown extensive area of the habitat in Switha Sound off Flotta.  The same survey  also identified new locations of tide-swept algal communities in the North Sound, north of Shapinsay and east of Graemsay (Figure 5).

Citizen science surveys have been responsible for all post-2012 records of seagrass beds in the SMR.  From 2012 - 2016 observations (principally by Seasearch surveys) have included new beds in Scapa Flow and in Bay of Tuquoy, Westray.  However, the bulk of recent records are derived from Seagrass Spotter observations (Seagrass Spotter, 2021) mostly from 2019, which include previously unknown locations for the habitat in the Bay of Firth (Mainland) and Shapinsay Sound.  Their recent observations in Deer Sound are supported by 2016 aerial imagery of the location, which appears to indicate very extensive distribution of the habitat.

Status and trend in grey and harbour seals

The Orkney Islands SMR is included in the Orkney and North Coast seal management area and as such there are not specific assessments of the status and trend in grey and harbour seals in this SMR.  Within the combined Orkney Islands and North Coast SMRs the number of grey seals is stable and their status is assessed as ‘few or no concerns’.  Harbour seal numbers were high and stable until the early 2000s but from 2005 onwards their numbers have been steadily declining and their status is assessed as ‘many concerns’.