Rockall Trough Seamounts and Banks IMMA

Size in Square Kilometres

106,464 km2

Qualifying Species and Criteria

Sperm whale – Physeter macrocephalus

Criterion A

Sei Whale – Balaenoptera borealis

Criterion A

Blue whale – Balaenoptera musculus

Criterion A

 Fin whale – Balaenoptera physalus

Criterion A

Marine Mammal Diversity 

Criterion D (2)

Physeter macrocephalus, Hyperoodon ampullatus, Ziphius cavirostris, Mesoplodon bidens, Globicephala melas, Balaenoptera borealis, Balaenoptera musculus, Balaenoptera physalus, Megaptera novaeangliae



This IMMA encompasses the waters around the seamount complex of the Rockall Trough, which has depths extending down to around 2000m.  The area includes the Anton Dohrn and Hebrides Terrace seamounts which rise steeply to depths of approx. 500m as well as Rosemary Bank, Bill Bailey’s Bank, Lousy Bank and the Wyville-Thompson ridge (at depths of 400m). These deep seamounts and ridges are known high-use habitats for deep-diving beaked whales and sperm whales (Physeter macrocephalus) that are considered Vulnerable on the IUCN Red List. The bathymetry and water currents within this area also encourage upwelling which can drive productivity that attracts baleen whales.  The area experienced heavy whaling in the early 20th century, and today this habitat supports recovering populations of Endangered blue (Balaenoptera musculus) and sei whales (Balaenoptera borealis) and Vulnerable fin whales (Balaenoptera physalus).

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The area is identified on the basis of important habitat for several species.  These include sperm whales (Physeter macrocephalus), which are listed as vulnerable by the IUCN Red List of Threatened Species (Taylor et al. 2019).

The area also supports several baleen whale species.  The fin whale (Balaenoptera physalus) is listed as vulnerable by the IUCN Red List of Threatened Species (Cooke, 2018a). The sei whale (Balaenoptera glacialis) and blue whale (Balaenoptera musculus) are currently listed as endangered on the IUCN Red List of Threatened Species (Cooke, 2018b, 2018c).

Whaling data from Scottish whaling stations (1903-1951) have demonstrated the importance of this region for these baleen whale species as well as for sperm and northern bottlenose whales (Thompson, 1928; Brown, 1976; Ryan et al. 2022), and recent surveys confirm their continued presence in the area (Weir et al., 2001; Pollock et al., 2000; Rogan et al., 2018; Berrow et al., 2018; Evans and Waggitt, 2020; Lacey et al., 2022). There is also acoustic data showing the regular presence of blue, fin, and humpback whales in this area (Charif et al., 2001; Charif & Clark, 2009).

Although not assessed as threatened on the IUCN Red List, beaked whales in this area are of particular concern due to large mortality events potentially associated with sonar exposure.  An unexplained mortality event of beaked whales: Cuvier’s (Ziphius cavirostris), Sowerby’s (Mesoplodon bidens) and northern bottlenose whales (Hyperoodon ampullatus) occurred adjacent to this region with 118 beaked whales stranded along the western UK seaboard in 2018 (SMASS 2018), compared to a mean annual record of 5 beaked whales stranding for the four preceding years.

Criterion D: Special Attributes

Sub-criterion D2: Diversity

The area hosts deep-diving sperm whales, northern bottlenose whales, Cuvier’s beaked whale, Sowerby’s beaked whale, long-finned pilot whales (Globicephala melas), which are often found along the continental slope in association with topographic singularities such as canyons, banks and seamounts that are within reach of their diving ability.  Various studies have documented high numbers of sightings and relative abundance for these species in the IMMA (Weir et al. 2001; Boisseau et al. 2011; Rogan et al. 2017; Berrow et al. 2018; Evans and Waggitt, 2020; Lacey et al. 2022).  All of these species dive to over 650m and use echolocation to locate their prey, generally deep-water cephalopods.  Pilot whales undertake deep dives just after sunset as the deep-scattering layer ascends, whereas beaked and sperm whales dive throughout the day.  Beaked whales are thought to forage benthically and leave marks observed at seamounts (Woodside et al. 2006).   Within the Ziphiidae and Physeteridae, the highest predicted densities based on habitat modelling in the eastern North Atlantic are also along the Trough and Shelf edge of this IMMA (Virgili et al. 2018).

The topographic features and currents around the seamounts and banks in the Rockall Trough create dynamic frontal zones and eddies which support densities of copepods that are also of interest for Sei whales, blue whales, fin whales and humpback whales (Ryan et al. 2022), which are frequently documented in visual surveys (Rogan et al., 2017; Berrow et al., 2018; Evans and Waggitt, 2020; Lacey et al., 2022) as well as by acoustic data (Charif et al., 2001; Charif & Clark, 2009).

There are even some reports of critically endangered North Atlantic right whales (Eubalaena glacialis) in the area (O’Cadhla et al., 2004; Evans & Waggitt, 2020).

Supporting Information

Berrow, S.D., O’Brien, J., Meade, R., Delarue, J., Kowarski, K., Martin, B., Moloney, J., Wall, D., Gillespie, D., Leaper, R., Gordon, J., Lee, A. and Porter, L. 2018. Acoustic Surveys of Cetaceans in the Irish Atlantic Margin in 2015–2016: Occurrence, distribution and abundance. Department of Communications, Climate Action & Environment and the National Parks and Wildlife Service (NPWS), Department of Culture, Heritage and the Gaeltacht, Dublin, Ireland, 348pp.

Bett, BJ. 2001. UK Atlantic Margin Environmental Survey: Introduction and overview of bathyal benthic ecology. Continental Shelf Research 21: 917–956

Boisseau, O., Moscrop, A., Cucknell, A., McLanaghan, R., and Wall, D. 2011. An acoustic survey for beaked whales in the Rockall Trough. SC-63-SM2. Available at:

Brown, S.G. 1976. Modern whaling in Britain and the north-east Atlantic Ocean. Mammal Review, 6: 25-36.

Charif, R.A. and Clark, C.W. 2009. Acoustic monitoring of large whales in deep waters north and west of the British Isles, 1996-2005. Cornell Lab of Ornithology Technical Report 08-07. 40pp.

Charif, R.A., Clapham. P.J., and Clark, C.W. 2001. Acoustic detections of signing humpback whales in deep waters off the British Isles. Marine Mammal Science, 17(4): 751-768.

Cooke, J.G. 2018a. Balaenoptera physalus. The IUCN Red List of Threatened Species 2018: e.T2478A50349982. Accessed on 11 April 2023

Cooke, J.G. 2018b. Balaenoptera borealis. The IUCN Red List of Threatened Species 2018: e.T2475A130482064. Accessed on 12 April 2023

Cooke, J.G. 2018c. Balaenoptera musculus (errata version published in 2019). The IUCN Red List of Threatened Species 2018: e.T2477A156923585. Accessed on 25 May 2023.

Ellett D.J., Kruseman, P., Prangsma, G.J., Pollard, R.T., Vanaken, H.M., Edwards, A., Dooley, H.D., Gould, W.J. 1983. Water masses and mesoscale circulation of North Rockall Trough waters during JASIN 1978. Phil Trans R. Soc. Lond A., 308: 231-252.

Evans, P.G.H and Waggitt, J.J. 2020. Impacts of climate change on marine mammals, relevant to the coastal and marine environment around the UK. MCCIP Science Review 2020, 421–455. doi: 10.14465/2020.arc19.mmm

Henry, L-A., Vad, J., Findlay, H.S., Murillo, J., Milligan, R., and Roberts, J.M. 2014. Environmental variability and biodiversity of megabenthos on the Hebrides Terrace Seamount (Northeast Atlantic). Scientific Reports 4, 5589 (2014).

Lacey, C, Hammond, PS, Gilles, A, Börjesson, P, Herr, H, Macleod, K, Ridoux, V, Santos, MB, Scheidat, M, Teilmann, J, Vingada, J, Viquerat, S, & Øien, N (2022). Modelled density surfaces of cetaceans in European Atlantic waters in summer 2016 from the SCANS-III aerial and shipboard surveys. SCANS-III project report 2. Available at:

Mackey, M., Perales i Giménez, D. and Cadhla, O.O.SEA678 Data Report for Offshore Cetacean Populations (Report). Coastal & Marine Resources Centre. Pdf available at:

O’Cadhla, O., Mackey, M., Aguilar de Soto, A., Rogan, E., and Connolly, N. 2004. Cetaceans and Seabirds of Ireland’s Atlantic Margin. Volume II. Cetacean Distribution & Abundance. Report on research carried out under the Irish Infrastructure Programme (PIP) Rockall Studies Group (RSG) projects 98/6 and 00/13, Porcupine Studies Group project P00/15 and Offshore Support Group (OSG) project 99/38. 82pp. Available at:

Paxton, C.G.M., Scott-Hayward, L.A.S. and Rexstad, E. (2014) Statistical Approaches to Aid the Identification of Marine Protected Areas with Regard to Minke Whale, Risso’s Dolphin, White-Beaked Dolphin and Basking Shark.Scottish Natural Heritage Commissioned Report No. 594. 132pp

Pollock, C.M., Mavor, R., Weir, C.R., Reid, A., White, R.W., Tasker, M.L., Webb, A., and Reid, J.B. (2000) The distribution of seabirds and Marine Mammals in the Atlantic Frontier, north and west of Scotland. Joint Nature Conservation Committee, Aberdeen. 92pp.

Rogan, E., Cañadas, A., Macleod, K., Santos, M.B., Mikkelsen, B., Uriarte, A., Van Canneyt, O., Vázquez, J.A., and Hammond, P.S. 2017. Distribution, abundance and habitat use of deep diving cetaceans in the North-East Atlantic.  Deep–Sea Research Part II, 141: 8–19

Rogan, E., Breen, P., Mackey, M., Cañadas, A., Scheidat, M., Geelhoed, S. & Jessopp, M. 2018. Aerial surveys of cetaceans and seabirds in Irish waters: Occurrence, distribution and abundance in 2015-2017. Department of Communications, Climate Action & Environment and National Parks and Wildlife Service (NPWS), Department of Culture, Heritage and the Gaeltacht, Dublin, Ireland. 297pp.

Ryan, C., Calderan, S., Allison, C., Leaper, R. and Risch, D. 2022. Historical occurrence of whales in Scottish Waters inferred from whaling records. Aquatic Conserv: Mar Freshw Ecosyst., 32:1675–1692.

SMASS 2018. Annual Report for Marine Scotland, Scottish Government.

Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. (2019). Physeter macrocephalus (amended version of 2008 assessment). The IUCN Red List of Threatened Species 2019: e.T41755A160983555. Accessed on 11 April 2023

Thompson, D.A. (1928) On whales landed at the Scottish whaling stations during the years 1908-1914 and 1920-1927. Sci Invest Fish Bd Scott 3. 3-40

Virgili, A., Authier, M., Boisseau, O., et al. 2019. Combining multiple visual surveys to model the habitat of deep‐diving cetaceans at the basin scale. Global Ecol Biogeogr., 28:300–314.

Weir, C.R., Pollock, C., Cronin, C. and Taylor, S. 2001. Cetaceans of the Atlantic Frontier, north and west of Scotland. Continental Shelf Research, 21: 1047-1071.

Woodside, J.M., David, L., Frantzis, A., Hooker, S.K. (2006) Gouge marks on deep-sea mud volcanoes in the eastern Mediterranean: Caused by Cuvier’s beaked whales? Deep-Sea Res Part I-Oceanogr Res Pap 53:1762-1771


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