Mayo to Shelf Edge Area of Interest for Marine Protected Area Designation

Size of the area: 7,210km²

The west coast of Ireland was identified as a high biodiversity ‘Area of Interest’ for potential Marine Protected Area designation, in our recent report ‘Revitalising Our Seas’. 

For the full site synopsis and references please find the relevant pages of the report PDF here. 


Why was this area identified as a potential Marine Protected Area?

This area has high densities of bottlenose dolphins that are present here year-round. Clew Bay is one of a few Irish bays in which the critically endangered angel shark (Squatina squatina) and flapper skate are still found. This area is the only breeding site in Ireland for the rare breeding Leach’s storm petrel (Hydrobates leucorhous).

Here’s an infographic summarising the key elements of this Area of Interest.

You can download this as a printable poster here.



Reefs of the native oyster (Ostrea edulis) occur in Clew Bay. These have become extremely rare in Irish waters and only occur in a few bays on the west coast. Blacksod Bay, which is already a Special Area of Conservation (SAC), once had a large, 855 ha, calcareous tube worm (Serpula vermicularis) reef, which has been completely destroyed by benthic dredging. Many species lived within this reef, either between or on the reef structures. The tube-forming worm reef was described as being encrusted with coralline algae and sponges, with red algae and anemones also growing on the reef. The reef was considered to be a keystone community that was of considerable importance to the overall ecology and biodiversity of the habitat by virtue of its physical complexity. Creating a Marine Protected Area (MPA) here may allow this reef to recover and the community of marine organisms that depended on it. Large seagrass and maerl beds also occur in Blacksod Bay, as well as the horse mussel (Modiolus modiolus). The area has a high variation in seabed substrate, from fine sand to rock, however, large parts of seabed substrate have not yet been classified. 


As the closest land point to the drop-off of the continental shelf, this area is a hive of seabird activity. Sightings of 27 species of seabirds are represented in this area, including 19 of the 24 species that breed in Ireland annually. The coastline of this area has a number of highly significant colonies. It is the only part of the country where Leach’s storm-petrel breeds each year, one of Ireland’s five ‘Birds of Conservation Concern’ red-listed seabird species. Important sites are Stags of Broadhaven and Bills Rocks. Numerous other inhabited and uninhabited islands and islets are attractive breeding sites for terns, auks, and fulmar. 

Leach’s storm petrel (Hydrobates leucorhous)

Elasmobranchs (sharks, skates, rays and chimaeras)

Clew Bay has been identified as a hotspot for the critically endangered angel shark (Squatina squatina) and a refuge for the flapper skate (Dipturus intermedius). Analysis of the Irish Whale and Dolphin Group (IWDG) database and ObSERVE survey data indicate high basking shark (Cetorhinus maximus) densities around Achill Island. While the area is not the highest in terms of sightings (6% of total basking shark sightings reported from this area), there are three sightings of between 10 and 20 individuals from the south coast of Achill Island and one sighting of 30 individuals in Broadhaven Bay. 

Cetaceans (whales, dolphins and porpoises) 

Proximity to the shelf edge results in high species diversity. Historically this was the site of Ireland’s most recent whaling stations, which hunted fin (Balaenoptera physalus), blue (Balaenoptera musculus), sei (Balaenoptera borealis) and sperm whales (Physeter macrocephalus) along the shelf edge. Compared with other sites, densities for bottlenose dolphins are relatively high here, distributed close to the coast and within the West Connacht Coast SAC (for which this species is the sole qualifying interest), and further south around Achill Island (3.87/100km2). Bottlenose dolphins spend the whole year in this area with higher sightings of the species recorded during the summer months. Lower densities of harbour porpoises exist within the site, however, sightings were recorded year-round with higher recordings during the summer months. Small numbers of long-finned pilot whales (Globicephala melas) were recorded within the site, with higher densities (0.71/100km2) observed closer to the shelf edge and further offshore. SCANS II surveys demonstrated that Atlantic-white sided dolphins (Lagenorhynchus acutus) also occur and use the AOI. Occasional sightings of killer whales were recorded close to the coast with higher counts during the summer months. White-beaked dolphins (Lagenorhynchus albirostris) occurred on occasion within the site, with one encounter of 35 animals off Clare Island. There were a small number of sightings of Risso’s dolphin, and small numbers of humpback whale sightings close to the coast. Common dolphins were distributed throughout the site and occurred year-round. Juveniles and calves were also recorded within this site between 2005 and 2021. 

Bottlenose Dolpins by Sibéal Regan

Commercially exploited species 

The area features herring spawning and nursery grounds and part of a whiting spawning ground on the north Mayo coastline. Recently, Fair Seas visited Tommy Flaherty, a fisherman from Inis Mór, Co. Galway. Tommy said that there was once a strong spawning ground for herring and fishing ground around the Bills at Achil. However, he says that today “the fish aren’t coming into the bay as they used to long ago”. 

With a properly managed network of Marine Protected Areas, these fish stocks and incredible species can be given the chance to recover. Allowing these species the chance to recover is essential if we are to support our small-scale artisanal fisheries and create new employment opportunities in rural areas such as through eco-tourism. To reverse biodiversity loss and tackle the climate crisis we need to allow nature and our wild ecosystems to recover which comes with added socioeconomic benefits to our communities. 

Fair Seas published the report Revitalising Our Seas in June 2022 and identified sixteen areas of interest for potential Marine Protected Area designation in Irish waters. The report aims to help kickstart the conversation around MPAs within the government and among stakeholders. MPAs can help to restore life in our seas to what they once were and can benefit coastal fisheries and local economies. 



Keep up to date with Fairseas and MPA news and developments, by subscribing up to our newsletter here. Make sure to follow us on Instagram, Twitter and Facebook.

We also welcome you to join us in Cork on 8th June, where we are hosting our inaugural World Ocean Day conference. We are bringing ocean advocates, government, industry and key stakeholders together to map out the next steps for Marine Protected Areas (MPAs) in Irish waters.

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