true

ISRA FACTSHEETS

EUROPEAN ATLANTIC

ISRA FACTSHEETS

EUROPEAN ATLANTIC

Porcupine Bank ISRA

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Porcupine Bank ISRA

Porcupine Bank

Summary

Porcupine Bank is located on the Irish continental shelf, ~200 kilometres west of Ireland. The area is characterised by seamounts and two large canyons and a diverse benthos. It is influenced by current circulation patterns, causing the accumulation of nutrient rich waters. The north of the area is dominated by hard ground, with small areas of soft sediment, while the southern part has soft sediment with occasional boulders and pebbles. Within this area there are: threatened species (e.g., Rabbitfish Chimaera monstrosa), reproductive areas (Bluntnose Sixgill Shark Hexanchus griseus), and the area sustains a high diversity of sharks (13 species).

Porcupine Bank

Porcupine Bank

DESCRIPTION OF HABITAT

Porcupine Bank is a raised area on the Irish continental shelf, ~200 km west of Ireland. It lies at the continental margin of the Northeast Atlantic and it slopes into the Rockall Trough to the west and Porcupine Seabight to the east. A large canyon runs through the area in a northeast-southwest direction, with depth ranging from ~500 m to >2,500 m. A second canyon occurs in the south of the area with depths >2,000 m. The area is characterised by seamounts midway along the main channel (NPWS 2024a).

Current circulation patterns around the Irish margin cause the accumulation of nutrient rich waters on the tops of banks, providing enriched food sources to the canyons and carbonate mounds occurring at the bank. The benthos is characterised by black, soft, and gorgonian corals, as well as sponges (including encrusting forms), desmospongia, and glass sponges (NPWS 2024b). The substrate in the north of the Porcupine Bank is dominated by hard ground, with small areas of soft sediment. The southern part of the area has soft sediment with occasional boulders and pebbles. Throughout the bank there are terraces, cliffs, overhangs, and boulders (NPWS 2024a).

This Important Shark and Ray Area is benthic, pelagic, and subsurface and is delineated from 200–1,500 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

Eight Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occur in the area. An additional three Qualifying Species considered threatened with extinction according to the Ireland Red List No. 11: Cartilaginous Fish regularly occur in the area. Threatened sharks comprise one Critically Endangered species and four Vulnerable species; threatened rays comprise two Critically Endangered species, two Endangered species, and one Vulnerable species; threatened chimaeras comprise one Vulnerable species (IUCN 2025).

CRITERION C

SUB-CRITERION C1 – REPRODUCTIVE AREAS

Porcupine Bank is an important reproductive area for two shark species.

Data were obtained from the Database of Trawl Surveys (DATRAS; ICES 2025). These surveys are conducted annually as part of an internationally coordinated bottom trawl survey programme.

Between 2010–2024, 583 neonate Blackmouth Catsharks were recorded from trawl surveys (ICES 2025). The size-at-birth for Blackmouth Catsharks is unknown, but these individuals measured <17 cm total length (TL), which is similar to the size-at-birth for congeners (Broadfin Sawtail Catshark Galeus nipponensis, 13 cm TL; Gecko Catshark G. eastmani, <17 cm TL; Atlantic Sawtail Catshark G. atlanticus, 15 cm TL; Ebert et al. 2021). These neonates were found in the area every year from 2010–2024 (2010: n = 23; 2011: n = 27; 2012: n = 30; 2013: n = 56; 2014: n = 87; 2015: n = 91; 2016: n = 72; 2017: n = 32; 2018: n = 48; 2019: n = 23; 2020: n = 7; 2021: n = 30; 2022: n = 21; 2023: n = 20; and 2024: n = 16).  These data were collected from standardised surveys which are conducted annually in September and October. Additional temporal data are required to confirm seasonality of the reproductive use of this area by this species. Further, in July 2021, the Marine Institute of Ireland’s SeaRover survey deployed a remotely operated vehicle (ROV) and captured footage of thousands of live Blackmouth Catshark egg cases within the area (Marine Institute 2022) highlighting the use of this area by pregnant females.

Overall, 175 Bluntnose Sixgill Sharks were recorded within the area. The vast majority (90%; n = 156) of them were estimated to be neonate/young-of-the-year (YOY) measuring <130 cm TL (size-at-birth of this species is estimated 61–74 cm TL; size-at-maturity is estimated at 310–330 cm TL for males and 400 cm TL for females; Ebert et al. 2021). Of these, 45 (28.8%) could be classed as neonates measuring <74 cm TL. Neonate/YOY Bluntnose Sixgill Sharks were recorded within this area every year from 2010–2024 (ICES 2025). In 8 of the 15 years in which Bluntnose Sixgill Sharks were captured in this area, all individuals were YOY/neonate (2010: n = 7; 2012: n = 13; 2013: n = 21; 2015: n = 6; 2018: n = 5; 2019: n = 13; 2020: n = 8; and 2021: n = 1). In the remaining 7 years in which Bluntnose Sixgill Sharks were captured in this area, the large majority of individuals captured were either YOY or neonate (2011: n = 9 out of 10; 2014: n = 8 out of 11; 2016 n = 14 out of 17; 2017 n = 6 out of 7; 2022 n = 4 out of 8; 2023 n = 8 out of 12; and 2024 n = 9 out of 15).

CRITERION D

SUB-CRITERION D2 – DIVERSITY

Porcupine Bank sustains a high diversity of Qualifying Species (13 species). This meets the regional diversity threshold (13 species) for the European Atlantic region.

Data between 2010–2025 from the Database of Trawl Surveys (DATRAS; ICES 2025) confirm the regular and predictable presence of these species in the area. These surveys are conducted annually as part of an internationally coordinated bottom trawl survey programme. Further data from Irish commercial fisheries collected between 2003–2021 also support the regular occurrence of these species.

Two threatened species are very common (i.e., averaging more than 100 occurrences per year in the 15 years analysed) in this area: Velvet Belly Lanternshark (n = 2,603 in 15 of 15 years) and Rabbitfish (n = 3,334 in 12 of 15 years). Two threatened species were found every year but in lower numbers due to lower population sizes: Sandy Skate (n = 170) and Cuckoo Skate (n = 366). An additional two threatened species occurred in nearly all of the years analysed: Kitefin Shark (n = 181 in 11 of 15 years) and Norwegian Skate (n = 79 in 12 of 15 years). The remaining six threatened species occur regularly and predictably but over fewer years or in lower numbers: Portuguese Dogfish (n = 74 in 6 of 15 years), Longnose Velvet Dogfish (n = 29 in 7 of 15 years), Common Blue Skate (n = 101 in 7 of 15 years), Flapper Skate (n = 68 in 8 of 15 years), and Spiny Dogfish (n = 93 in 8 of 15 years). Two non-threatened species are regularly and predictably found in the area: the Bluntnose Sixgill Shark (n = 175 in 15 of 15 years) and the Blackmouth Catshark (n = 28,680 in 15 of 15 years).

Porcupine Bank

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