South-West Deeps (West) MPA


Status: Marine Conservation Zone (MCZ)Click to link to the interactive map


South-West Deeps (West) MCZ is an offshore site situated to the south west of England, approximately 230 km from Land’s End in Cornwall.


The site protects approximately 1800 km2 of continental shelf seabed that is predominantly sandy with coarse and mixed sediments across the site extent forming different habitats. These habitats are known to support a range of animal species, including those which live within the sediments, such as small burrowing worms and bivalve molluscs to urchins, starfish and some crustaceans that live on the sediment surface. Furthermore, the site protects the geologically important large Celtic Sea Relict Sandbanks.


More detailed site information can be found on the Summary tab.


Map displaying MPA boundary and associated

protected feature data. Further data will be

available in due course. Visit the JNCC MPA Mapper

 to further view and explore data for this MPA.


Legislation behind the designation: Marine and Coastal Access Act (2009)


Protected features

EUNIS Code: Protected Features Feature Type General Management Approach
(to achieve conservation objective)
A5.1: Subtidal coarse sediment Broad-Scale Habitat

Recover to favourable condition

A5.2: Subtidal sand Broad-Scale Habitat

Recover to favourable condition

A5.3: Subtidal mud Broad-Scale Habitat

Recover to favourable condition

A5.4: Subtidal mixed sediments Broad-Scale Habitat

Recover to favourable condition

Fan mussel (Atrina fragilis) Species Feature of Conservation Interest

Recover to favourable condition

Celtic Sea Relict Sandbanks Geomorphological Feature

Maintain in favourable condition


The acquisition of new data may result in updates to our knowledge on feature presence and extent within this site. The most up to date information is reflected on the map on this page and in JNCC’s MPA mapper and the evidence underpinning this can be viewed in the Evidence tab.


Conservation objectives
The overarching conservation objectives for the designated features of all protected sites in UK offshore waters is to ensure they either remain in, or reach favourable condition. The ability of a designated feature to remain in, or reach favourable condition can be affected by its sensitivity to pressures associated with activities taking place within or in close proximity to a protected site. Information on the conservation objectives relating to this MCZ is provided in the Conservation Advice tab.

Site Timeline

The diagram below is a summary of the key milestones involved in the selection and designation of South-West Deeps (West) MCZ.  More detail can be found within the Relevant Documentation.

South West Deeps (West) timeline

Relevant Documentation

The documents referred to below and any other historical documents relating to South-West Deeps (West) MCZ were produced during the selection and designation process and therefore may be out of date.  This Site Information Centre is the most up to date source of information for this MPA, and will reflect any additional information gathered since these documents were produced. Further information about the Marine Conservation Zone site selection process and historic MCZ advice is available on the JNCC MCZ pages.





Last updated: October 2017


The information for this site summary was adapted from Regional MCZ project report and documentsin the Evidence tab.


Site overview

South-West Deeps (West) MCZ is situated approximately 230 km offshore from the south-west of England. The site is an area of continental shelf that is predominantly sandy with a mixed distribution of coarse and mixed sediments across the site extent. The geomorphological feature, Celtic Sea Relict Sandbanks, runs down the length of the site, from north to south. The sand banks are some of the largest examples of this feature on Earth and some of the ridges extend up to 200 km long, 15 km wide and 50 m high.


The site protects subtidal habitats that are representative of offshore habitats in UK waters. This includes the protection of almost 1500 km2 of Subtidal sand, as well as Subtidal coarse sediment and Subtidal mixed sediments. These habitats support a range of animal species including polychaete worms, veneroid molluscs and echinoderms, including sea urchins and starfish. Cnidarians, such as anemones, are also present alongside a variety of crustaceans and fish species, including the Cuckoo ray (Leucoraja naevus) and Monk or Angler fish (Lophius piscatorius).


A detailed survey was undertaken in May 2013 after the site had been advised upon by JNCC for designation by Defra and the resulting data confirmed the presence of Subtidal mud (40.31 km2), an additional broad-scale habitat, and Mud Habitats in Deep Water, a habitat Feature Of Conservation Importance (FOCI). This survey also identified the presence of a species FOCI, the Fan Mussel, Atrina fragilis. These two features were added to the South-West Deeps (West) MCZ Designation Order in Tranche Two of MCZ designations in 2016.


South-West Deeps (West) MCZ is situated 200km from East of Haig Fras MCZ, which was also designated in November 2013, and 132km North West from North-West of Jones Bank MCZ. These sites contribute to connectivity and representativity of the features within the Western Channel and Celtic Sea biogeographic area. Further detail on the evidence for this MCZ can be found on the Evidence tab.


Site location:  Coordinates for this MCZ can be found in the Designation Order listed in the Relevant Documentation.

Site area:  1824 km2 South-West Deeps (West) MCZ is similar in size to the Yorkshire Dales National Park (1769 km2) in the north of England.

Site depth range:  South-West Deeps (West) MCZ varies in depth from between approximately 100 m depth in the north east of the site, to 200 m depth in the southern part of the site.

Charting Progress 2 Biogeographic Region: Western Channel and Celtic Sea.


Site boundary description
The western boundary of South-West Deeps (West) MCZ aligns with the UK Continental Shelf boundary and the site polygon is completed by three simple straight lines. The boundary is in accordance with the MCZ Ecological Network Guidance, which advises using a minimum number of simple lines to delineate the site. As the site is adjacent to the UK Continental Shelf boundary, the boundary of the site was amended to align with the UK Continental Shelf boundary when it changed in 2014.




Last updated: October 2017


Site specific data
There is a range of data that underpin this MCZ. The full overview of the data used to support site identification, along with information on confidence in feature presence and extent is available in the 2013 JNCC Post-Consultation Advice. JNCC will be adding relevant survey data for this MPA to our JNCC MPA mapper in due course. Some of the data for this MCZ has been collected through JNCC funded or collaborative surveys and some through other means.  Data from these surveys provide direct evidence confirming the presence of the protected features within the site.


Survey and data gathering

  • South-West Deeps (West) MCZ verification survey (2013) - JNCC and Cefas collaborated on this survey, which was conducted in two parts by Gardline (10th February – 25th March 2013) and Cefas (7th May – 28th May 2013). The primary objective of this survey was to collect multibeam echosounder bathymetric and backscatter data and photographic ground truthing data to increase confidence in the spatial extent of South-West Deeps (West) MCZ designated features.
  • British Geological Survey particle size analysis data - Supporting information on the presence and extent of the broad-scale habitats Subtidal coarse sediment, Subtidal sand and Subtidal mixed sediments was provided by particle size analysis  of sediment samples from historical BGS surveys.


Data analysis reports

  • South-West Deeps (West) MCZ Post-survey site report (2015) - Data from the 2013 verification survey has been analysed by Cefas. The analysis confirms the presence of subtidal coarse sediment, subtidal sand and subtidal mixed sediments. The analysis also identified the presence of an additional broad-scale habitat, Subtidal mud, and the Features of Conservation Importance (FOCI) the Fan mussel (Atrina fragilis). Please note that all the information contained in this Site Information Centre only refers to the three broad-scale habitats and Celtic Sea Relict Sandbanks geomorphological feature designated in 2013.
  • Community analysis of South-West Deeps (West) MCZ data (2014) - JNCC contracted Seastar Survey Ltd to complete a community analysis of offshore MCZ grab and video data to establish biotopes. The following biotopes were recorded in South West Deeps (West) MCZ:
  • SS.SCS.OCS A5.15: Deep circalittoral coarse sediment

  • SS.SSa.OSa A5.27: Deep circalittoral sand

  • SS.SMx.OMx A5.45: Deep circalittoral mixed sediments

  • SS.SMx.OMx.PoVen A5.451: Polychaete-rich deep Venus community in offshore mixed sediments

  • SS.SMx.OMx.Csmi A5.45x: Deep circalittoral mixed sediment with Caryophyllia smithii (possible new biotope)

  • SS.SSa.OSa.(Ech) A5.27x: Deep circalittoral sand with heart urchins (possible new biotope)

  • SS.SSa.OSa.(Pex) A5.27x : Deep circalittoral sand with Paraphellia expansa (possible new biotope)

  • SS.SSa.OSa / SS.SMu.OMu A5.27: Deep circalittoral sand / A5.37: Deep circalittoral mud

  • Mapping seabed sediments of the Swallow Sand and South-West Deeps (West) MCZs (2014) - JNCC commissioned the British Geological Survey to undertake geostatistical mapping of the seabed sediments.
  • EUSeaMap (2016) - Supporting information on the presence and extent of subtidal coarse sediment, subtidal sand, subtidal mud and subtidal mixed sediments from a predictive seabed habitat map of European waters.
  • Mapping of Geological and Geomorphological Features (MB0102 Task 2A) (2009) - Defra commissioned a collation of data to map geological and geomorphological features, including the Celtic Sea Relict Sandbanks.


Additional relevant literature

References for further supporting scientific literature consulted during the identification of this site can be found in the annexes of our advice. Please be aware that although these sources contain information in relation to this MPA, they do not necessarily represent the views of JNCC.


Knowledge gaps
If you are aware of any additional data or relevant scientific papers for this site not listed in the Relevant Documentation, including the South-West Deeps (West) MCZ advice document, please contact JNCC.


Conservation Advice


Last updated: October 2017


Conservation objectives
Conservation objectives set out the desired state for the protected features of an MPA. The Conservation Objectives for the protected features of the MCZ are:


Subject to natural change, the Subtidal coarse sediment, Subtidal sand, Subtidal mud and Subtidal mixed sediments feature is to remain in or be brought into favourable condition, such that it's:

  • Extent is stable or increasing; and
  • Structures and functions, its quality, and the composition of its characteristic biological communities are such as to ensure that it is in a condition which is healthy and not deteriorating.


Subject to natural change, the Fan mussel (Atrina fragilis) feature is to remain in or be brought into favourable condition, such that the:

  • Quality and quantity of its habitat and the composition of the population are such that they ensure that the population is maintained in numbers which enable it to thrive


Subject to natural change, the Celtic Sea Relict Sandbanks interest feature is to remain in or be brought into favourable condition, such that it's:

  • Extent, component elements and integrity are maintained;
  • Structure and functioning are unimpaired; and
  • Surface remains sufficiently unobscured for the purposes of determining whether the conditions in the points above are satisfied.


More information regarding the conservation objectives for the protected features of South-West Deeps (West) MCZ is available in the site Designation Order, In addition to the conservation objectives above, General Management Approaches (GMAs) have been set by JNCC for each feature which provide a view as to whether a feature needs to be maintained in or be brought into favourable condition i.e. recover, based on our knowledge about its condition. For more information on the General Management Approach for MCZs see Defra’s MCZ Designation Explanatory Note.


The GMAs for the protected features of the MPA are:

  • Subtidal coarse sediment: Recover to favourable condition;
  • Subtidal sand: Recover to favourable condition;
  • Subtidal mud: Recover to favourable condition;
  • Subtidal mixed sediment: Recover to favourable condition;
  • Fan mussel (Atrina fragilis): Recover to favourable condition; and
  • Celtic Sea Relict Sandbanks: Maintain in favourable condition.

More information on the GMAs for the features in South-West Deeps (West) MCZ are provided in JNCC’s Tranche One post-consultation scientific advice to Defra and the Tranche Two pre-consultation and post-consultation scientific advice to Defra.

Advice on operations 

Section 127 of the Marine & Coastal Access Act (2009) states that JNCC may provide advice and guidance regarding matters capable of damaging or otherwise affecting the protected features of an MCZ. JNCC has published the following advice on activities which are capable of damaging or otherwise affecting protected features in MCZs:

JNCC provides a list of activities occurring within the South-West Deeps (West) MCZ and information on management within the Activities and Management tab. JNCC has provided this to aid the cumulative assessment of impacts of human activities within the site.  While every attempt has been made to ensure this information is accurate and kept up-to-date, the list is not to be considered exhaustive or definitive. The list does not, for example, include activities occurring off-site which may also be capable of affecting the protected features.


For the most up-to-date information about the biological communities present within the site and their spatial distribution, please see the Evidence tab. Sensitivity information for the protected features within the site can be found in a Technical Report (Tillen et al., 2010) commissioned by Defra to support the MCZ designation process. The information contained within the data and evidence tab, the activities and management tab, the Tillen et al. (2010) report and the advice listed above on activities which are capable of damaging or otherwise affecting the protected features in Tranche 1 MCZs are useful if you are:

  • Carrying out any activity that may impact the protected features of the site and need to find out how to operate within the law;
  • An authority providing advice on specific proposals; and/or
  • An authority responsible for putting management measures in place.


Our scientific understanding of the ecology of the protected features of the site and how activities can affect them may change over time. Similarly the activities taking place within the site may also change over time. JNCC’s conservation advice will be kept under review and will be periodically updated to reflect this. Further information on JNCC’s conservation advice work is available on the offshore MPA conservation advice webpage.

Activities and Management


Last updated: June 2017


Management status: Progressing towards being well managed


The vulnerability assessment conducted for this site suggests it is unlikely to be moving towards its conservation objectives, but directed site condition monitoring data are needed to improve our confidence in this assessment. Progress is ongoing with regards to the recommendation of a fisheries management proposal to the European Commission.


This site forms part of the UKs contribution to the OSPAR commission’s network of MPAs and the Emerald network established under the Bern Convention. As the UK is a member of the OSPAR commission, JNCC are committed to ensuring that the OSPAR MPA network is ‘well-managed’ by 2020.


JNCC consider ‘well-managed’ to mean the timely progress of an MPA around the ‘MPA management cycle’. This involves:

  1. The documentation of appropriate management information - conservation objectives, advice on activities capable of affecting the protected features of a site, and spatial information on the presence and extent of the protected features of a site.
  2. The implementation of management measures - management actions considered necessary to achieve the conservation objectives of a site.
  3. Site condition monitoring programmes – collecting the information necessary to determine progress towards a sites conservation objectives.
  4. Assessment of progress towards conservation objectives – using available information to infer whether or not a site is moving towards or has achieved its conservation objectives.


The sub-sections that follow provide an account of the progress of South-West Deeps (West) MCZ around each of these four stages in the MPA management cycle:


The documentation of appropriate management information

  • The conservation objectives and advice on activities capable of affecting the conservation status of the protected feature of this site are available under the conservation advice tab.
  • JNCC are in the process of improving our MPA conservation advice packages. Further information is available on our conservation advice pages.
  • Spatial information on the presence and extent of the protected feature of this MPA is available via JNCCs MPA mapper.
  • JNCC are in the process of developing downloadable MPA data packages where appropriate permissions to share datasets are in place.


The implementation of management measures

This section details progress towards the implementation of management measures for activities considered capable of affecting the conservation status of the protected features of the site. The protected features of the site are considered to be sensitive to pressures associated with fishing and ‘licensable’ activities.



  • Vessel monitoring data indicates that bottom trawling, pelagic fishing and the use of static gear types occur within the site which is potentially damaging to the habitats present at South-West Deeps (West) MCZ.
  • This MCZ falls outside the UK’s 12 nautical mile limit and is to be exclusively managed under the EU Common Fisheries Policy. In accordance with Article 18, requests for management will be developed jointly between the UK Government and any Member States with a direct management interest in the area affected. The Marine Management Organisation (MMO) are the lead authority regarding the implementation of, and compliance with, any measures to managing fishing activity. Further information on progress is available via MMO webpages.


Licensable activities

  • Whilst licensable activities such as oil and gas exploration and production do not take place within South-West Deeps (West) MCZ at present, any future proposals would be managed in accordance with the clauses set out under Section 127 of The Marine & Coastal Access Act (2009). Under this clause, JNCC have a statutory responsibility to advise the regulator on developments that are capable of affecting (other than insignificantly) the protected features of the MPA and that may hinder the achievement of the sites conservation objectives. JNCC consider that the existing marine licensing process is sufficient to ensure the management of licensable activities taking place, or that could take place in the future, on the protected features of this MPA.
  • For further information, please see the MMO’s guidance on marine conservation zones and marine licensing.
  • Further information on JNCC’s role in the provision of advice for licensed activities in the UK offshore area is available on JNCC’s offshore industries advice webpage


Telecommunications cables

  • One telecommunications cable currently crosses through the MPA.
  • Cables are largely an unregulated activity in offshore waters depending upon the type of cable being laid (or maintained), where it is being laid between and whether the cable is part of a larger development (which may be regulated). Any cable not directly associated with an energy installation does not require a marine license beyond 12 nautical miles.
  • JNCC encourages early discussion from operators regarding any plans related to new or existing cables, and encourages the undertaking of non-statutory environmental impact assessments for new or existing cable projects to assess their effect on the protected features of the MPA.



  • There is a radio calling-in point present in the site boundary and parts of the site may be crossed by ships.
  • Under international law, ships have a right of passage at sea including in areas designated as MPAs (unless management specifies the restriction of ship transiting as outlined through an International Maritime Organisation measure). The pressures associated with shipping activity within South-West Deeps (West) MCZ are not considered likely to impact the protected features of the site.


Military activity

  • The MCZ is within a MoD exercise area and MoD activities are known to take place in the water column above the site.
  • The MoD has incorporated all designated MPAs into their Environmental Protection Guidelines (Maritime) and wider Marine Environmental and Sustainability Assessment Tool. These guidelines are used to manage MoD activity to minimise the associated risks to the environment.


Site condition monitoring

Site condition monitoring surveys are yet to take place within this MPA. Further information will be made available under the Monitoring tab in due course. A summary of our existing knowledge base for this site is provided in the Evidence tab.


Progression towards conservation objectives

No long-term condition monitoring data is available to determine whether the MPA is moving towards or has reached its conservation objectives. The site has a ‘recover’ conservation objective based on a vulnerability assessment that examined exposure to activities associated with pressures to which the protected features of the site are considered sensitive. This suggests the site is unlikely to be moving towards its conservation objectives but site condition monitoring data would improve our confidence in this assessment. Further information will be provided under the Assessment tab as it becomes available.



Last updated: October 2017


JNCC is currently leading on the development of a strategy for biodiversity monitoring across all UK waters, to include MPA monitoring. For MPAs, data and evidence collected from monitoring activities will aim to:

  • Enable assessment of condition of the features within sites;
  • Enable assessment of the degree to which management measures are effective in achieving the conservation objectives for the protected features;
  • Support the identification of priorities for future protection and/or management; and,
  • Enable Government to fulfil its national and international assessment and reporting commitments in relation to MPAs and help identify where further action may be required.


Information on monitoring of this MPA will be provided when it becomes available. 




Last updated: October 2017


Assessments of the condition of designated features in offshore MPAs are required to report against our legal obligations. Ideally these assessments should be based on observed data, and then measured against targets for predefined indicators. However, for MPAs in offshore waters we do not always have the appropriate information to be able to do so. This is particularly true for seabed habitats, which are the main type of feature designated for protection in offshore MPAs. 


To address these challenges, JNCC has been an active partner in the development of new approaches and tools for the assessment of habitats and species for a variety of national and international status reports. They include the second cycle of the Conservation Status Assessment reports under the EU Habitats Directive, Charting Progress 2 (CP2) and the OSPAR Quality Status Report (QSR). JNCC continues to develop and pilot tools for the assessment of marine habitats and species in offshore waters to improve the quality and transparency of our offshore MPA assessments, and contribute to the monitoring of marine biodiversity in UK waters. These tools cover methods for producing interim assessments of site features and their responses to pressures, as well as developing more robust indicators for determining condition of the features.


Under the UK Marine & Coastal Access Act (2009), JNCC is required to report to Ministers on the degree to which the  conservation objectives of the protected features of Marine Conservation Zones (MCZs) have been achieved.  Every 6 years from 2012, the Marine Act requires a report setting out how MCZs have performed against their conservation objectives, as well as the effectiveness of the network as a whole. The assessments of features within MPAs will also feed into six yearly reports on the state of the marine environment under the Marine Strategy Framework Directive (MSFD), which aims to achieve Good Environmental Status (GES) by 2020.



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