Location and physical characteristics
Figure 1: North Coast Scottish Marine Region.The thicker white line delineates the extent of the North Coast SMR. For a map of all SMRs and OMRs, see Figure 5 here
| Coastline length (km) | 544 |
| Sea area (km2)Â Â | 2,443 |
| Deepest point (m) | 124 |
| Shallowest point (m)Â | coastline |
| Average depth (m)Â | 68 |
| Tides (m) | 2.1 – 4.3 |
| Salinity | 34.49 – 34.85 |
| Sea surface temperature (°C) | 7.8 – 13.7 |
The North Coast SMR extends along Scotland’s north coast (Figure 1). Strong tidal currents run through the Pentland Firth, situated between the mainland and the Orkney Islands, in an east-west direction with the residual to the east and into the North Sea. These are some of the fastest tidal currents in the world, reaching over 8 m/s. The region only has a small amount of freshwater input. The north facing coast is exposed to wind and waves, mostly from the north and east.
Seabed sediments between Cape Wrath and Dunnet Head consist of a zone up to 15 km wide of gravels and sandy gravels. The strong currents that flow through the Pentland Firth result in patchy sediment cover with rock outcrops on the seabed. Sandbanks and sand-wave fields occur to the west and south east of the Pentland Firth. In most areas offshore, bedrock is covered by seabed sediments and infill sediments, but isolated rock outcrops may occur.
Productive
The North Coast SMR stretches the length of the north coast of the Scottish mainland. The border between this SMR and the Orkney Islands SMR passes through the Pentland Firth where the annual mean-depth average peak tidal current speed at spring tide can exceed 4.5 m s-1 (See Scotland’s Tidal Stream Resource case study). This predictable energy resource, although it fluctuates with four peaks every day, is being explored as part of Scotland’s future energy supply.Â
The North Coast SMR, has a major ferry route running from the north coast (Scrabster) to Orkney (Stromness). In 2018 153,000 passengers were carried by ferries operating in the North Coast SMR.
As well as being a ferry port, Scrabster had a total fish landings of 20,665 tonnes in 2018, the bulk of which is demersal fish.
The Productive Assessment has been undertaken, with a focus on 2014 – 2018, on a sectoral basis. As mentioned, for some Sectors, including oil and gas, carbon capture and storage and aggregates, there was no activity within the North Coast SMR during the period 2014 – 2018.
However, for many sectors, there were changes over the period 2014 – 2018 (Figure 2). Atlantic salmon production, the length of subsea active power cables and the rod and line catch all decreased. In contrast, fish landings and marine passenger transport increased.
Figure 2: Changes that have taken place in the North Coast SMR by Sector.
Although the period 2014 – 2018 inclusive has been used where possible, there are some entries when a slightly different time period has been used. Information on Atlantic salmon production, mussel production and pacific oyster production for the North Coast SMR has been merged with the West Highlands SMR to avoid disclosure. Information on seaweed harvesting for the North Coast SMR has been merged with the Moray Firth SMR to avoid disclosure.
Pressures from human activities
As part of SMA 2020, an assessment of the main pressures from human activities in each of the Scottish Marine Regions and Offshore Marine Regions was undertaken through a MASTS-led workshop. The process and outcomes are presented in detail in the Pressure from Activities section. Five main pressures identified for the North Coast SMR ordered as per the MASTS-led Pressure Assessment Workshop were:
| Priority [1] | Pressure (FeAST classification) [2] | Main healthy and biologically diverse components affected [3] | Main contributing FeAST activity /activities to pressure [4] | Associated productive assessments [5] |
|---|---|---|---|---|
| 1 | Removal of target species (including lethal) |
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| 2 | Removal of non-target species (including lethal) |
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| 3 | Physical change (to another seabed type) |
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| 4 | Surface/Sub-surface abrasion/penetration |
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| 5 | Underwater noise |
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Clean and safe
The assessments cover eutrophication, hazardous substances, marine litter, noise and microbiology and algal toxins which have the potential to impact on habitats and species as well as being a consequence of human activity. Although sources of litter or contaminants may be local, there are cases when the source is some distance from the impacted area. The main findings for the North Coast SMR are:
Eutrophication
The North Coast showed no evidence of eutrophication as a consequence of nutrient enrichment. However, there was a statistically significant increasing trends in nutrient inputs although loads were an order of magnitude lower than most other SMRs. This increase was attributed to an increase in riverine inputs in the region. Winter nutrient concentrations and chlorophyll concentrations were below assessment criteria and relatively stable. There were no dissolved oxygen data for the North Coast.
Hazardous substances
Hazardous substances (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and heavy metals (Hg, Cd and Pb)) assessments in sediment and biota (fish and shellfish) were undertaken at the scale of the five Scottish biogeographic regions: Atlantic North-West Approaches, Irish Sea (Clyde and Solway), Minches and Western Scotland, Scottish Continental Shelf and Northern North Sea. The North Coast SMR is in the Scottish Continental Shelf biogeographic region. There are limited biota and sediment sites in the Scottish Continental Shelf biogeographic region, and no sites in the North Coast SMR. Where contaminants were measured in the Scottish Continental Shelf, biogeographic region concentrations were generally above background but below concentrations where adverse effects could occur. In addition, there were no increasing trends, and for lead inputs there was a significant decreasing trend which is related to decreasing river inputs.
Of the biological effects measurements included in the assessment, there are no sites in the North Coast SMR and also limited data at the biogeographic region scale for the Scottish Continental Shelf. External fish disease, a general measure of fish health, was assessed at one site in the Scottish Continental Shelf biogeographic region and showed that the fish health status was satisfactory. However ,this site was not in the North Coast SMR.
Marine litter
Due to the lack of assessment criteria for marine litter, beach litter and microplastic, status assessments were not possible. However, litter and microplastics are present in all SMRs, including the North Coast. The North Coast SMR has a relatively low concentration of microplastics in surface water (< 5,000 microplastics per km2 of sea surface).
Seafloor litter was assessed at the scale of the biogeographic regions; The North Coast SMR is in the Scottish Continental Shelf biogeographic region. The evidence indicates that there are apparent decreases in sea-loor litter density over time between 2012 to 2018.
Beach litter data were not available for the North Coast SMR.
Noise
There are limited noise data for the North Coast; no continuous noise data were collected and there are very few impulsive noise data for this region. It is not possible to do a status assessment as there are no assessment criteria to say what levels of noise are harmful, and not enough years of data to carry out a trend assessment.
Microbiology and algal toxins
There were 2 bathing waters in the North Coast SMR that were assessed according to levels of Escherichia coli and intestinal enterococci, one was classified as Excellent and one Good in the latest classification (2018).
Escherichia coli is monitored in shellfish as a proxy of the microbiological quality of the water from shellfish production areas. Classifications are awarded according to the Food Standards Scotland (FSS) Protocol for Classification and Management of Escherichia coli. A site can be designated A, B, C, A/B or B/C, with Class A products able to go direct for human consumption. Three sites were monitored in the North Coast SMR, with no site having prohibited levels of Escherichia coli.
A number of marine algal species produce biotoxins which, by accumulation in bivalve molluscs such as mussels and oysters, can cause human illness when these shellfish are eaten. Both biotoxins and phytoplankton are routinely monitored in classified shellfish production areas under Regulation (EU) 2017/625. Such monitoring takes place at three sites within the North Coast SMR. Concentrations of diarrhetic shellfish toxins (DSTs) exceeded regulatory limits (RL) in 2015 and 2018, and paralytic shellfish toxins were reported above RL in 2017. No samples exceeded RL for amnesic shellfish toxins.
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Healthy and biologically diverse
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 three MPAs in the North Coast 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. 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 regional totals. Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole. Â
Table 1. Numbers of types of MPAs in the North Coast SMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.
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Type of MPA |
Abbr. |
Total no. of MPAs |
No. of new MPAs 2012-2018 |
|
Special Area of Conservation |
SAC |
1 |
0 |
|
Special Protection Area |
SPA |
2 |
0 |
The MPAs are focused on the protection of breeding seabirds, otters and offshore reefs.
The North Caithness Cliffs SPA and Cape Wrath SPA, situated at the north-easternmost and north-westernmost respectively extremities of mainland Scotland, support internationally important numbers of breeding seabirds, especially gulls and auks. During the breeding season, these seabirds forage over large areas of sea returning frequently with food to feed their chicks. Durness SAC is designated for the population of otters that frequent the coast.
Progress in managing MPAs
The progress in implementing management for MPAs in the North Coast 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 North Coast 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.
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Type of MPA |
Spatial measures in place pre-2012 |
New spatial measures in place 2012-2018 |
Spatial measures in discussion 2012-2018 |
No. of MPAs monitored by statutory bodies 2012-2018 |
No. of MPAs monitored via citizen science 2012-2018 |
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Special Area of Conservation |
0 |
0 |
0 |
Habitats |
1 |
Habitats |
0 |
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Special Protection Area |
0 |
0 |
0 |
2 |
0 |
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| Â | Â | Â | Â | Â | Â | Â | Â |
There are currently no spatial measures in place or under discussion for any of the MPAs in this SMR. All of the MPAs have been monitored at least once during the assessment period with the main focus on breeding seabirds.
Information on MPA boundaries can be viewed in Marine Scotland’s NMPi. To find out more about specific MPAs, please visit NatureScot’s SiteLINK.Â
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 blue mussel beds, horse mussel beds, maerl beds and seagrass beds have been recorded within the SMR, no data are available on temporal changes in extent of these habitats and hence no status assessments could be made; the other biogenic habitats i.e. serpulid aggregations, flame shell beds and intertidal seagrass beds have not been recorded in this SMR. Modelling work was carried out as part of the assessment to predict the extent of physical disturbance to the seafloor more generally.
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.
Predicted habitat disturbance by mobile demersal fishing for the North Coast SMR is close to the average for SMRs in terms of the proportion of the seabed with 49% high disturbance compared to the average of 50% for all SMRs (Figure X). Only 5% of the seabed is predicted to experience no disturbance (average of 12% for all SMRs). Disturbance levels closely mirror the degree of surface abrasion and are relatively heavy in the central part of the SMR where the substrate is predominantly sand, and lighter towards the eastern and particularly western side where coarse sediments predominate.Â