Biscay Abyssal Plain IMMA

Size in Square Kilometres

216,173 km2

Qualifying Species and Criteria

Sperm whale – Physeter macrocephalus

Criterion A, B (2)

Fin whale – Balaenoptera physalus

Criterion A, B (2)

Striped dolphin – Stenella coeruleoalba

Criterion B (2)

Marine Mammal Diversity 

Criterion D (2)

Balaenoptera physalus physalus, Physeter macrocephalus, Stenella coeruleoalba, Delphinus delphis, Tursiops truncatus, Grampus griseus, Globicephala melas, Balaenoptera acutorostrata, Balaenoptera musculus, Balaenoptera borealis, Ziphius cavirostris, Megaptera novaeangliae, Orcinus orca



The abyssal plain of the Bay of Biscay hosts a large number of fin whales (Balaenoptera physalus), which concentrate in the area in the summer. It is estimated that more than 10,000 fin whales, which are considered Vulnerable on the IUCN Red List of Threatened Species, aggregate in this area. For centuries commercial whaling efforts were concentrated in the IMMA and surrounding areas. Since the cessation of whaling, large-scale dedicated scientific surveys and citizen science efforts conducted from platforms of opportunity, have revealed a high density of fin. The area also encompasses the highest densities of sperm whales (Physeter macrocephalus) in the North East-Atlantic. In addition, a dozen of additional species of cetaceans are encountered on this area, including common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), bottlenose dolphins (Tursiops truncatus), Risso’s dolphins (Grampus griseus), Long-finned pilot whales (Globicephala melas), killer whales (Orcinus orca), minke whales (Balaenoptera acutorostrata), Cuvier’s beaked whales (Ziphius cavirostris) and more rarely blue whales (Balaenoptera musculus).

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

This IMMA is identified on the basis of important habitat for North Atlantic fin whales, (Gilles et al., 2023; Hammond et al., 2009; Lacey et al., 2022) which are considered Vulnerable on the IUCN Red List of Threatened Species (Cooke, 2018).  The IMMA also encompasses highly preferential habitat for sperm whale (Physeter macrocephalus) (Rogan et al., 2017; Virgili et al., 2022), which is also considered vulnerable on the IUCN Red List of Threatened Species (Taylor et al. 2019).

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

Fin whales are known to aggregate in the IMMA during summer months, based on evidence from several large scale European ship and aerial surveys (SCANS I in 2005, CODA in 2007, SCANS II in 2016 and SCANS III in 2022(Gilles et al., 2023; Hammond et al., 2009; Lacey et al., 2022)) as well as French surveys, SAMM, of the eastern part of the IMMA (Laran et al., 2022, 2017). f Predicted density from the SCANS III survey included densities of greater than 0.075 individuals/km² within the limit of the IMMA (Lacey et al., 2022), and the species showed the least variation in predicted distribution between surveys of any of the species modelled (Lacey et al., 2022). A compilation of data from a wide range of methods clearly underlines the species’ oceanic distribution (Evans & Wagitt, 2020), which is also highlighted in encounter rates from long-term citizen science platform of opportunity surveys (2007-2022) by ORCA (Matear et al, 2019).

During SCANS III (summer 2016) density was estimated as 0.073 (CV=29%) over the oceanic strata of the Bay of Biscay (Hammond et al, 2021), corresponding to an estimated 10,600 individuals in this area (95% Convidence Interval 5,800-19,200).  It is suspected that these individuals migrate out of the area during winter months, as only a small number of encounters were observed during the SAMM-II winter survey (2021) in the eastern part of the IMMA (Laran et al, 2017; 2020).

Results from large-scale surveys conducted in the North Atlantic have reported a concentration of sperm whales in deep ocean waters off Galicia (western Spain) and in the Bay of Biscay (Rogan et al, 2017; Virgili et al 2022, Evans 2021). The total abundance of sperm whales in the area is estimated to be 3,267 (CV = 0.23) individuals. Adjusting this estimate to include a proportion of sightings of unidentified large whales, the abundance reaches 7,035 (CV = 0.28) sperm whales (Rogan et al., 2017).

Finally, surface modelling conducted by Lacey et al. (2022) indicated that the IMMA also hosts a high density of striped dolphins (Stenella coeruleoalba) (> 0.15 ind.km²).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

This candidate IMMA contains habitat that supports an important diversity of cetacean species. In addition to fin whales, sperm whales and striped dolphins, the Bay of Biscay abyssal plain hosts at least a dozen species of cetaceans, including Cuvier’s beaked whales (Ziphius cavirostris), common dolphins (Delphinus delphis), bottlenose dolphins (Tursiops truncatus, listed in the Annexe II of European Habitat directive), long-finned pilot whales (Globicephala melas), Risso’s dolphins (Grampus griseus), minke whales (Balaenoptera acutorostrata), Endangered Sei whales (Balaenoptera borealis) (Hammond et al., 2017, 2009, 2007; Laran et al., 2017; Rogan et al., 2017) and more rarely blue whales (Balaenoptera musculus) (Gilles et al., 2023; Laran et al., 2017).  Killer whales (Orcinus orca) and humpback whales (Megaptera novaeangliae) are also encountered in the area (

Supporting Information

Caballero, A., Ferrer, L., Rubio, A., Charria, G., Taylor, B.H., Grima, N., 2014. Monitoring of a quasi-stationary eddy in the Bay of Biscay by means of satellite, in situ and model results. Deep-Sea Res. II 106, 23–37.

Cooke, J.G. 2018. Balaenoptera physalus. The IUCN Red List of Threatened Species 2018: e.T2478A50349982. Accessed on 18 December 2023.

Evans, P.G.H., Carrington, C., and Waggitt, J. (2021) Risk Assessment of Bycatch of Protected Species in Fishing Activities. European Commission, Brussels. 213pp. MAPPING REPORT.pdf

Gilles, A., Authier, M., Ramirez-Martinez, N., Araújo, H., Blanchard, A., Carlström, J., Eira, C., Dorémus, G., Fernández-Maldonado, C., Geelhoed, S., Kyhn, L., Laran, S., Nachtsheim, D., Panigada, S., Pigeault, R., Sequeira, M., Sveegaard, S., Taylor, N., Owen, K., Saavedra, C., Vázquez-Bonales, J., Unger, B., Hammond, P., 2023. Estimates of cetacean abundance in European Atlantic waters in summer 2022 from the SCANS-IV aerial and shipboard surveys (Final report). University of Hannover.

Hammond, P. S., Lacey, C., Gilles, A., Viquerat, S., Borjesson, P., Herr, H., Macleod, K., Ridoux, V., Santos, M.B., Scheidat, M., Teilmann, J., Vingada, J., Øien, N., (2021). Estimates of cetacean abundance in European Atlantic waters in summer 2016 from the SCANS-III aerial and shipboard surveys. Available at:

Hammond, P.S., Berggren, P., Borchers, D., Burt, L., Cañadas, A., Desportes, G., Donovan, G., Gilles, A., Gillespie, D., Gordon, J., Hedley, S., Hiby, A.J., Kuklik, I., Leaper, R., Lehnert, K., Leopold, M., Lovell, P., Macleod, K., Øien, N., Paxton, C., Ridoux, V., Rogan, E., Samarra, F., Scheidat, M., Sequeira, M., Siebert, U., Skov, H., Swift, R., Tasker, M., Teilmann, J., Van Canneyt, O., Vásquez, J.A., 2007. Abundance of harbour porpoise and other small cetaceans in the European Atlantic and North Sea.

Hammond, P.S., Macleod, K., Gillespie, D., Swift, R., Winship, A., Burt, M.L., Cañadas, A., Vázquez, J.A., Ridoux, V., Certain, G., Van Canneyt, O., Lens, S., Santos, B., Rogan, E., Uriarte, A., Hernandez, C., Castro, R., 2009. Cetacean Offshore Distribution and Abundance in the European Atlantic (CODA)., Final report.

Lacey, C., Hammond, P., Gilles, A., Börjesson, P., Herr, H., MacLeod, K., Ridoux, V., Santos, B.M., 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).

Laran, S., Authier, M., Blanck, A., Doremus, G., Falchetto, H., Monestiez, P., Pettex, E., Stephan, E., Van Canneyt, O., and Ridoux, V. (2017) Seasonal distribution and abundance of cetaceans within French waters- Part II: The Bay of Biscay and the English Channel. Deep Sea Research Part II: Topical Studies in Oceanography 141, 31-40.

Laran, S., Genu, M., Authier, M., Blanchard, A., Dorémus, G., Sanchez, T., Spitz, J., Van Canneyt, O., 2022. Distribution et abondance de la mégafaune marine en France métropolitaine. Rapport final de la campagne SAMM II Atlantique-Manche – Hiver 2021. Observatoire Pelagis (UAR 3462, La Rochelle Univ-CNRS) pour la Direction de l’Eau et de la Biodiversité et OFB.

Lens, S. (2007). The Bay of Biscay: from whaling to whalewatching. In -. Centro Oceanográfico de Vigo.

Matear, L, James R. R., Michelle H., and Potts J. 2019. Cetacean Biodiversity in the Bay of Biscay: Suggestions for Environmental Protection Derived from Citizen Science Data. Marine Policy 109 (): 103672.

Pelagis (2021). Visual sightings of scientific surveys. Accessed 25th May 2023.

Pingree, R.D., Garcia-Soto, C., 2014. Plankton blooms, ocean circulation and the European slope current: response to weather and climate in the Bay of Biscay and W English Channel (NE Atlantic). Deep Sea Res. Part II: Top. Stud. Oceanogr. 106 (0), 5–22.

Rogan, E., Cañadas, A., Macleod, K., Begoña Santos, M., Meikkelsen, B., Uriarte, A., Van Canneyt, O., Antonio Vasquez, J., Hammond, P.S., 2017. Distribution abundance and habitat use of deep diving cetaceans in the North-East Atlantic. Deep-Sea Res. II Top. Stud. Oceanogr. 141, 8–19.

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 18 December 2023.

Virgili, A., Teillard, V., Dorémus, G., Dunn, T.E., Laran, S., Lewis, M., Louzao, M., Martínez-Cedeira, J., Pettex, E., Ruiz, L., Saavedra, C., Santos, M.B., Van Canneyt, O., Vázquez Bonales, J.A., Ridoux, V., 2022. Deep ocean drivers better explain habitat preferences of sperm whales Physeter macrocephalus than beaked whales in the Bay of Biscay. Sci. Rep. 12.

Waggitt, J.J., Evans, P.G., Andrade, J., Banks, A.N., Boisseau, O., Bolton, M., Bradbury, G., Brereton, T., Camphuysen, C.J., Durinck, J. and Felce, T., (2020). Distribution maps of cetacean and seabird populations in the North‐East Atlantic. Journal of Applied Ecology 57(2):253-269


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