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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, especially in the summer.


Map displaying the North Anglesey Marine MPA boundary. Visit JNCC's MPA Mapper to view and download the 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

North Anglesey Marine 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  Natural Resource Wales and JNCC


Harbour Porpoise SACs video



Last updated: March 2023

Key features of North Anglesey Marine SAC
Size 3,249 km2 
Latitude, Longitude (centre) 53.5663, -4.8279
Depth Range Mean Low Water to 100m below sea-level
Habitat type(s) Mix of hard substrate, course sediment and mud
Biogeographic Region(s) Irish Sea region


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 (Phocoena phocoena) in the summer months. The site 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.

The North Anglesey Marine SAC fully encompasses the Croker Carbonate Slabs SAC which was designated for submarine structures made by leaking gases. It also encompasses the Irish Sea Front Special Protection Area (SPA), designated for Manx shearwater and partially overlaps the Anglesey Terns SPA.

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 Monitoring and Evidence section.


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


Site Boundary  

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.


Conservation objectives

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.

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 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. Supplementary advice 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 and proposed activity which may significantly harm a sites designated features is subject to a Habitats Regulation Assessment (HRA). Retained EU Regulation 2019/1241 prohibits most net fishing practices across part of the site between February and April. Fishing restrictions can be viewed in full using the Kingfisher Fishing Restriction Map.


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).


Activities and Management

Last updated: March 2023

Summary of the medium to high pressures towards Harbour porpoise in the North Anglesey Marine 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.

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 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.

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


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. 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. 

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 information contained within the Conservation Objectives and Advice on Operations document and Monitoring and Evidence section 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 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 Habitats and Species Regulations 2017 (as amended). 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.


Monitoring and Evidence

Last updated: March 2023

Site Identification and Selection

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).

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 survey data analyses and subsequent modelling underpinned the identification of the North Anglesey Marine SAC as an area with persistently higher density of porpoises in relation to other areas.



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 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.

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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