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North Anglesey Marine MPA

The North Anglesey Marine SAC extends from the northern coast of the Isle of Anglesey into the Irish Sea, and has been identified as an area of importance for harbour porpoise.

Status: Special Area of Conservation (SAC)

Designated: February 2019


Stretching from the northern coast of the Isle of Anglesey into the Irish Sea, the North Anglesey Marine SAC has been identified as an area of importance for harbour porpoise, covering an area almost five times the size of Anglesey.

The North Anglesey Marine SAC overlaps a range of other habitats, including coarse and sandy sediments, rock, and mud. Encompassed within the site is the Croker Carbonate Slabs SAC which was designated for submarine structures made by leaking gases.

More detailed site information can be found within the Summary section below.

Map displaying the North Anglesey Marine MPA boundary and associated protected feature data. Visit JNCC's MPA Mapper to further view and explore data for this MPA.



Legislation behind the designation: European Commission Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora, commonly known as the 'Habitats Directive'. The EU Habitats Directive (1992) was transposed into UK law by The Conservation of Habitats and Species Regulations 2017 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.


Protected Features

Feature Feature Type Management Unit Conservation Objective
Harbour porpoise
Phocoena phocoena
Annex II Species Celtic and Irish Seas
Management Unit
Maintain site integrity


Conservation objectives

To ensure that the integrity of the site is maintained and that it makes an appropriate contribution to maintaining Favourable Conservation Status (FCS) for harbour porpoise in UK waters.


Harbour Porpoise SACs video


Site Timeline

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

December 2014
Site submitted as initial advice to Government.
June 2015
Site formally recommended to UK Government as draft Special Area of Conservation (SAC).
Formal public consultation. Site becomes 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 formally designated by the UK as a Special Area of Conservation (SAC).


Relevant Documentation

Some documents below, relating to the North Anglesey Marine 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 2016.

Site documents:


Identification and selection process:

Further documents relating to the evidence and analysis can be found in the Evidence section, whilst documents published during the public consultation in 2016 can be found on the archived consultation page. Information about the SAC site selection process is available on JNCC's SAC webpages.



Last updated: October 2017

The information for this site summary was adapted from documents listed in the Relevant Documentation section and incorporates any further information gathered since these documents were produced.

Site overview

The North Anglesey Marine SAC has been designated for the protection of the harbour porpoise Phocoena phocoena, and is estimated to support 2.4% of the UK Celtic and Irish Seas Management Unit (MU) population. Situated off the northwest corner of Wales, this site extends from the Anglesey coast into the offshore waters (> 12 nm) between Ireland and the Isle of Man, and it is therefore the joint responsibility of both Natural Resources Wales (NRW) and JNCC to provide statutory advice.

Covering an area of 3,249 km2, this sites spans water depths which range from the Mean Low Water (MLW) level down to 100 m along the western boundary, though much of the site is 50 m or shallower. The site covers a mix of habitats, including areas of rock, coarse and sandy sediments, and mud.

Survey data collated through the Joint Cetacean Protocol (JCP) were analysed to identify areas with persistently high harbour porpoise occurrence. The modelled outputs of this analysis demonstrate that the North Anglesey Marine 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 North Anglesey Marine SAC was based on data collected during the SCANS-II survey, which took place in July 2005. Further detail on the evidence for this SAC can be found in the Evidence section.

Site location: The boundary of this SAC are available to view and download via JNCC's MPA Mapper. Co-ordinates for this SAC are available from the Selection Assessment Document listed in the Relevant Documentation section.

Site area: This site has an area of 3,249 km2.

Site depth range: The site ranges from Mean Low Water to 100 m below sea-level.

Charting Progress 2 Biogeographic Region: Irish Sea region.

Site boundary description: The North Anglesey Marine 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.



Last updated: October 2017

Data gathering and analysis

A range of data underpin this SAC, as described below. 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 (collect from coastal locations).

  • Sea-based data were collated through the Joint Cetacean Protocol (JCP), created in 2004, which is amongst the largest collation 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. DHI (UK) Ltd (DHI) were contracted by JNCC to undertake an analysis of these data in order to identify persistent areas of higher harbour porpoise density around the UK.
  • Land-based survey data were compiled from a wide range of UK sources; this was part of a contract with a consortium led by Sea Watch Foundation to analyse these data as an aid to identifying coastal areas of importance to harbour porpoises. Data for the analyses came from 678 locations and amounted to over 75,000 hours of survey effort and around 50,000 sightings over a 20-year period (1994–2014).

The survey data analyses underpinned the identification of the North Anglesey Marine SAC as an area with persistently higher density of porpoises in relation to other areas (IAMMWG, 2015). 

For further information on the data used and the process applied to identify the SAC, please consult the North Anglesey Marine 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). Further documents are also listed below in support of the identification of the North Anglesey Marine SAC:


Additional relevant literature

References for further supporting scientific literature consulted during the identification of this site can be found in the North Anglesey Marine SAC Selection Assessment Document. lease be aware that although these sources contain information in relation to this MPA, they do not necessarily represent the views of JNCC.

  • Management Units for cetaceans in UK waters (JNCC Report No. 547, 2015) – Description of the Management Units (MUs) for the seven most common cetacean species in UK waters, including harbour porpoise. The Management Unit is the spatial scale defined as the most appropriate scale to apply management for a species considering abundance and distribution.


Knowledge gaps

If you are aware of any additional data or relevant scientific papers for this site made available since 2011 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.


Conservation Advice

Last updated: March 2019

Conservation objectives

Conservation objectives set out the desired state for the protected feature(s) of an MPA. The conservation objectives for the protected feature of the North Anglesey Marine Special Area of Conservation (SAC) are available within the Conservation Objectives and Advice on Operations document.

This information is useful 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.

The conservation objectives for the North Anglesey Marine 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:

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

JNCC is working to provide more detailed advice on the interpretation of the conservation objectives listed above. Supplementary advice is available in the Conservation Objectives and Advice on Operations document, and updates will be provided here when available.


Advice on Operations

In line with Regulation 21 of The Conservation of Offshore Marine Habitats and Species Regulations 2017which apply to the UK’s offshore marine area, and Regulation 37(3) of The Conservation of Habitats and Species Regulations 2017, which apply to Welsh inshore waters, the advice on operations for the protected feature of the North Anglesey Marine 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 the scientific knowledge of harbour porpoise of JNCC and Natural Resources Wales 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 Evidence section.

The advice on operations summarises ongoing activities occurring within or close to the site, with an assessment as to whether they pose a risk to harbour porpoise. This information is useful 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.  

The information contained within the Conservation Objectives and Advice on Operations document and Evidence section are useful 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 of the site, its integrity and its qualifying feature and how activities can affect it may change over time. The conservation advice provided by JNCC and Natural Resources Wales will be kept under review and will be periodically updated to reflect this and surveillance required under Article 17 of the Habitats Directive. Conservation advice for sites which straddle the 12 nm boundary will continue to be developed jointly with the relevant country nature conservation body. Further information can be found on the Natural Resources Wales website.


Activities and Management

Last updated: June 2020

To ensure the site contributes in the best possible way to achieving Favourable Conservation Status, the Relevant and Competent Authorities should consider the need for managing human activities within their remit which might affect (directly or indirectly) the integrity of the site, with regards to its Conservation Objectives. JNCC, along with other statutory nature conservation bodies (SNCBs), advises those authorities on the need for managing activities.

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 was provided on a noise management approach to keep underwater noise 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.   

Natural Resources Wales will provide separate advice for sites which are their joint responsibility with JNCC and/or Natural England.

Harbour porpoise SACs noise guidance and supporting documents


Further information on conservation advice in relation to this MPA can be found in the Conservation Advice section.



Last updated: October 2017

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.



Last updated: October 2017

Every six years, Member States are required under Article 17 of the EU Habitats Directive to report on the conservation status of habitats and species listed under Annex I and II. For harbour porpoise, the Article 17 assessments consider conservation status both within the Natura 2000 network and in the wider sea with particular emphasis placed on status and trends in terms of population size, range and habitat quality. These assessments will also feed into six-yearly reports on the state of the marine environment under the Marine Strategy Framework Directive (MSFD).


Published: .

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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