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Southern North Sea MPA

The Southern North Sea SAC has been identified as an area of importance for harbour porpoise. This site falls off the east coast of England and includes key winter and summer habitat for this species. 


Map displaying the Southern North Sea MPA boundary. Visit JNCC's MPA Mapper to view and download site boundary for this site.






The conservation objectives for the sites are to maintain site integrity by ensuring:

  1. Harbour porpoise are a viable component of the site
  2. There is no significant disturbance of the species
  3. The condition of supporting habitats and processes, and the availability of prey is maintained


Southern North Sea SAC Factfile
Designation Special Area of Conservation (SAC)
Date of Designation February 2019

Harbour porpoise (Phocoena phocoena)

Feature Status Favourable
Site Status Favourable
Site Management  JNCC and Natural England


Harbour Porpoise SACs video



Last updated: March 2023

Key features of Southern North Sea SAC
Size 36,951 km2 
Latitude, Longitude (centre) 53.551, 1.7999
Depth Range Mean Low Water to 75m below sea-level
Habitat type(s) Course sediment, sand and gravel beds
Biogeographic Region(s) Southern North Sea and Northern North Sea regions


The Southern North Sea SAC lies along the east coast of England, predominantly in the offshore waters of the central and southern North Sea, from north of Dogger Bank to the Straits of Dover in the south. This site stretches from the central North Sea (north of Dogger Bank) to the Straits of Dover in the south, covering an area of 36,951 km2, making it the largest SAC in UK and European waters at the point of designation in 2019.

The Southern North Sea SAC is an area of importance for harbour porpoise, supporting an estimated 17.5% of the UK North Sea Management Unit (MU) population. Approximately two-thirds of the site, the northern part, is recognised as important for porpoises during the summer season, whilst the southern part supports persistently higher densities during the winter. The majority of this site lies offshore but does extend from the coastal areas of Norfolk and Suffolk out to the 12 nautical mile limit. Therefore, both Natural England and JNCC are responsible for providing statutory advice.

The SAC ranges in depth from Mean Low Water down to 75 m, with the majority of the site shallower than 40 m, and is characterised by its sandy, coarse sediments which cover much of the site. These physical characteristics are thought to be preferred by harbour porpoise, likely due to availability of prey.

The site overlaps with Dogger Bank SAC; Haisborough, Hammond and Winterton SAC; and North Norfolk Sandbanks and Saturn Reef SAC.



Protected Features

Feature Feature Type Management Unit Feature Status
Harbour porpoise
(Phocoena phocoena)
Annex II Species North Sea
Management Unit


Site Boundary

The Southern North Sea SAC boundary was defined based on predicted areas with high densities of harbour porpoise identified through data modelling over an 18-year period. As a general principle, site boundaries were drawn tightly around the qualifying feature. The seaward boundaries were drawn using straight lines where possible; however, a balance was needed between more-complex site shapes drawn tightly around the feature and simple square/rectangular boundaries, so that the area of ‘non-interest-feature’ within the boundary was reduced. Further boundary principles were developed due to the nature of the modelled output. The modelling approach used 5 x 5 km grids, and so the model output was “blocky”, and further boundary smoothing methods were applied to simplify the boundary, without altering the site area by more than 5%. Coastal edges were defined by the “Mean Low Water” (MLW) tide line.


Conservation Objectives

The conservation objectives (CO) for the Southern North Sea SAC are: to ensure that the integrity of the site is maintained and that it makes the best possible contribution to maintaining Favourable Conservation Status (FCS) for harbour porpoise in UK waters. In the context of natural change, this will be achieved by ensuring that:

  • CO 1.  Harbour porpoise is a viable component of the site.
  • CO 2. There is no significant disturbance of the species.
  • CO 3. The condition of supporting habitats and processes, and the availability of prey is maintained.

Conservation objectives set out the desired state for the protected feature(s) of an MPA. The conservation objectives for the protected feature of the Southern north Sea Special Area of Conservation (SAC) are further explained in the Conservation Objectives and Advice on Operations document.

This information should be referred to if you are:

  • Preparing Habitats Regulations Assessments (HRAs) of proposed plans or projects that may affect the site;
  • Planning measures to maintain or restore the site and its qualifying feature;
  • Monitoring the qualifying features; and/or
  • Developing, proposing or assessing an activity, plan or project that may affect the site.

JNCC is working to provide more detailed advice on the interpretation of the conservation objectives listed above, and updates will be provided here when available.



Legislation behind the designation: The EU Habitats Directive 1992 transposed into UK law by The Conservation of Habitats and Species Regulations 2017 and subsequent Amendment (2019) within 12 nautical miles (nm), and The Conservation of Offshore Marine Habitats and Species Regulations 2017 between 12 nm out to 200 nm or the UK Continental Shelf

Legislation on site management: Under the Conservation of Habitats and Species Regulations (2017) any proposed activity which may significantly harm a sites designated features is subject to a Habitats Regulation Assessment (HRA). Where the site overlaps with the Dogger Bank and Haisborough, Hammond and Winterton SACs, it is subject to The Dogger Bank SAC Bottom Towed Fishing Gear Bylaw (2022) and Haisborough, Hammond and Winterton European Marine Site Bottom Towed Fishing Gear Byelaw (2014).

More information on impact management can be found in the Activities and Management section



Site Timeline

The diagram below is a summary of the key milestones involved in the selection and designation of the Southern North Sea SAC.  More detail can be found in the Relevant Documentation section or in the sections below.

December 2014
Site submitted as initial advice to UK Government.
June 2015
Site formally recommended to the UK Government as a draft Special Area of Conservation (SAC).
Formal public consultation. Site becomes a possible SAC. Post-consultation advice submitted to UK Government.
Site submitted to the European Commission. Site becomes a candidate SAC / Site of Community Importance (cSAC/SCI).
February 2019
Site is formally designated as a SAC by UK Government.


Activities and Management

Last updated: March 2023

Summary of the medium to high pressures towards harbour porpoise in the Southern North Sea SAC, adopted from table 1 of the Advice on Operations document:

Pressure Potential Impact Relative Risk of Impact
Entanglement/Bycatch Mortality
Contaminants Effects on water and prey quality
Bioaccumulation through contaminated prey ingestion 
Anthropogenic underwater sound Mortality
Internal injury
Disturbance leading to behavioural changes
Habitat changes/loss
Reduction in prey resource Reduction in food availability
Increased competition 
Displacement from natural range
Collision with vessels or installations Mortality
Disclaimer; this information is adapted from the Conservation Objectives and Advice on Operations document, published in 2019.


In June of 2020, JNCC together with Natural England (NE) and the Department of Agriculture, Environment and Rural Affairs in Northern Ireland (DAERA) published advice to competent authorities on what could constitute Significant Disturbance within harbour porpoise SACs in England, Wales and Northern Ireland marine areas. In addition, guidance on noise management in harbour porpoise SACs (JNCC Report No. 654, 2020) was provided to ensure underwater noise remains within levels that do not affect a site’s integrity. The advice and guidance are the culmination of several years of inter-agency discussion as well as consultation with regulators, industry and Non-Governmental Organisations. JNCC, NE and DAERA are committed to periodically reviewing this advice to ensure it remains workable, effective and takes account of best-available evidence.


Advice on Operations 

The Conservation Objectives and Advice on Operations document summarises ongoing activities occurring within or close to the site, with an assessment as to whether they pose a risk to harbour porpoise. It is recommended that this information is used when assessing an activity, plan or project which may affect the protected features and 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.

In line with Regulation 21 of the Conservation of Offshore Marine Habitats and Species Regulations 2017, which apply to the UK’s offshore marine area, and Regulation 37(3) of the Conservation of Habitats and Species Regulations 2017, which apply to English inshore waters, the advice on operations for the protected feature of the Southern North Sea SAC outlines knowledge of the nature and extent of activities taking place at the time of writing which may have a significant impact on the feature for which a site has been selected.

The advice on operations is based on JNCC’s and Natural England’s scientific knowledge of harbour porpoise at the time of writing, and their sensitivities to pressures. For the most up-to-date information about harbour porpoise within the site and the spatial distribution, please see the Monitoring and Evidence section.

The information contained within the Conservation Objectives and Advice on Operations document, the Activities and Management and the Monitoring and Evidence sections should be referred to if you are:

  • Carrying out any activity that may impact 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 and integrity of the site, how it is used by harbour porpoise and how activities can affect it may change over time. Conservation advice produced by JNCC and Natural England will be kept under review and will be periodically updated to reflect this and subsequent surveillance requirements under Habitats and Species Regulations 2017 (as amended). Conservation advice for sites which straddle the 12nm boundary will continue to be developed jointly with the relevant country nature conservation body. Further information can be found on Natural England’s website.


Monitoring and Evidence

Last updated: March 2023

Site Identification and Selection

Given the extensive range and mobility of harbour porpoise, analyses to underpin site identification were completed at a UK scale; localised datasets were not used in isolation to define the boundaries of this SAC. Two types of data have been analysed to investigate harbour porpoise persistent densities in UK waters; these are effort-related sea-based data (collected from ships and aircraft) and effort-related land-based data (collected from coastal locations).

The Joint Cetacean Protocol (JCP), when created in 2004, represented one of the largest collations of standardised survey data on harbour porpoise in the world. Comprising 39 data sources with data from at least 545 distinct survey platforms (ships and aircraft), representing over 1 million km of survey effort (coverage) over an 18-year period from 1994–2011. Survey data collated through the Joint Cetacean Protocol (JCP) were analysed to identify discrete and persistent areas of high harbour porpoise density in UK waters (JNCC Report 544, 2015). The modelled outputs of this analysis demonstrate that the Southern North Sea SAC persistently contains densities of porpoises which are within the top 10% of those for the Management Unit. The population estimate for harbour porpoise in the Southern North Sea SAC was based on data collected during the SCANS-II survey which took place in July 2005.

For further information on the data used and the process applied to identify the SAC, please consult the Southern North Sea Selection Assessment Document, and Section two of ‘The use of harbour porpoise sightings data to inform the development of Special Areas of Conservation in UK waters’ (JNCC Report No. 565, 2015).

Further documents in support of the selection of the Southern North Sea SAC are also listed in Relevant Documentation section. 



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

  • Enable assessment of the status 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 SAC will be provided here when it becomes available.

The UK Marine Strategy (UKMS) is a three part framework for achieving good environmental status (GES) in our seas. It is comprised of an assessment of current state of current state, updated on a 6 year cycle. In addition the strategy provides  a guide to UK marine monitoring programmes and a programme of measures to gauge progress towards GES. The assessment was last updated in 2019 and work is currently underway to develop the next stage of UKMS. 


Monitoring Programmes

This section details ongoing marine monitoring programmes in the UK. Though these programmes are not focused on the SAC area, the outputs can be used to understand the status of the site and harbour porpoise.

There have been several wide scale dedicated surveys for monitoring the distribution and abundance of cetaceans in UK waters, namely Small cetaceans in the European Atlantic and North Sea (SCANS) and Cetacean Offshore Distribution and Abundance in the European Atlantic (CODA). The surveys provide robust estimates of abundance for use in status and impact assessments. The survey cycle for widescale UK cetacean surveys is outlined below.

Year Survey Link
2022 SCANS IV Currently underway
2007 CODA Cetacean Offshore Distribution and Abundance (2009)
2005 SCANS II Cetacean Abundance and Distribution (2013)
1994 SCANS Updated analysis within Cetacean Abundance and Distribution (2013)

The Joint Cetacean Data Programme (JCDP) vision is to standardise and improve access to cetacean surveys data from across the Northeast Atlantic. The JCDP aims to provide a wider evidence base for site assessments as the resource grows.

The Cetacean Strandings Investigation Programme (CSIP) has led the recording and investigation of stranded cetaceans in England since 1990. The programme is responsible for monitoring general health as well as pressures from bycatch, pollution and infectious disease.

The UK Bycatch Monitoring Programme is run by the Sea Mammal Research Unit (SMRU) and deploys on-board observers onto fishing vessels to monitor bycatch events of selected protected species.

Clean Catch UK is a collaborative research programme aimed at reducing and eliminating accidental capture of wildlife in the UK fishing industry.

Vessel Monitoring Systems (VMS) and Inshore Vessel Monitoring Systems (I-VMS) are used to monitor fishing activities in UK waters. 

The Marine Noise Registry was developed by Defra and the JNCC to record impulsive noise arising from human activities in UK seas. It aims to quantify the pressure on the environment of relevant impulsive sound sources throughout the year. This in turn aids the definition of baseline levels for impulsive noise in UK waters.


Relevant Documentation

Some documents below, relating to the Southern North Sea SAC, were produced during the selection and designation process and therefore may not be updated from point of submission to Europe in January 2017. This Site Information Centre is the most up-to-date source of information for this site and will reflect any additional information gathered since our advice to Government in September 2016.

Some documents below, relating to the Southern North Sea SAC, were produced during the selection and designation process and therefore may not be updated from point of submission to Europe in January 2017. This Site Information Centre is the most up-to-date source of information for this site and will reflect any additional information gathered since our advice to Government in September 2016.

Conservation advice documents:

Evidence documents:

Site identification and selection process documents:



Knowledge Gaps

If you are aware of any additional data or relevant scientific papers for this site made available since designation that we may not be aware of, please contact us. Please note that due to the process of identifying boundaries, data are unlikely to impact the boundaries of the site, but may be used to support management decisions.


Published: .

Reviewed: .

This Site Information Centre (SIC) was created and last substantially updated prior to the end of the Transition Period following the UK’s exit from the European Union (31 December 2020). Therefore some of the content may still refer to EU legislation and management proposals or commitments which were correct at the time that the content was last updated. These references will be revised as necessary when the SIC is next substantially revised. Requirements through EU legislation are being retained in the UK so existing environmental protections and standards remain, and the protection given to habitats and species continues.

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