Northern Continental Shelf of the Bay of Biscay IMMA
Size in Square Kilometres
123,155 km2
Qualifying Species and Criteria
Common dolphin – Delphinus delphis
Criterion B (2)
Harbour porpoise – Phocoena phocoena
Criterion B (2)
Marine Mammal Diversity
Criterion D (2)
Delphinus delphis, Phocoena phocoena, Tursiops truncatus, Grampus griseus, Globicephala melas, Balaenoptera acutorostrata, Balaenoptera physalus, Stenella coeruleoalba, Halichoerus grypus, Ziphius cavirostris, Megaptera novaeangliae, Kogia sp.
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Summary
This IMMA includes waters from the coast to the edge of the continental shelf, connecting the Bay of Biscay, the English channel and the South of Celtic Sea. More than ten species of marine mammals are observed regularly in the area and have been extensively documented through a series of standardised surveys since 2005. The northwestern portion of the area contains high densities of common dolphins (Delphinus delphis), whilst the eastern part of the English Channel hosts high concentrations of harbour porpoises (Phocoena Phocoena) in winter. The broad continental shelf of the Bay of Biscay shows particularly well-marked seasonality in its oceanographic conditions, with a strong phytoplankton bloom in spring driving high productivity throughout the summer.
Description of Qualifying Criteria
Criterion B: Distribution and Abundance
Sub-criterion B2: Aggregations
Several large-scale surveys have documented the distribution and abundance of marine mammals in the IMMA, particularly in summer. European surveys include CODA-2016 (Hammond et al., 2009), SCANS II summer 2005 (Hammond et al, 2013), SCANS III summer 2016 (Hammond et al., 2017; Lacey et al., 2022)), and SCANS IV summer 2022 (Gilles et al, 2023) as well as the French aerial surveys, SAMM, in the Bay of Biscay and English Channel in winter 2011–2012, summer 2012 (Lambert et al, 2017; Laran et al, 2017) and winter 2021 (Laran et al, 2022a).
Aerial surveys in 2016 yielded an abundance estimate for common dolphins in European continental shelf and offshore waters of 467,000 dolphins (CV=0.26) with the majority of sightings in the Bay of Biscay and coastal waters of France and Spain (Hammond et al. 2017). Several large scale surveys indicate that common dolphins aggregate in the IMMA in summer (Gilles et al., 2023; Hammond et al., 2017; Lacey et al., 2022; Laran et al., 2017, 2022b), which is also confirmed by relatively high encounter rates from long-term citizen science platform of opportunity surveys (ORCA, 2007-2022, Robbins, Babey & Embling, 2020).
Common dolphins are also found in important concentrations in this IMMA in winter months. Results from aerial surveys in winter 2011-12 and a dramatic increase in bycatch from fisheries in winter 2021 (Peltier et al., 2021) suggest a change in common dolphin distribution in the area, with groups spread over the entire shelf area in winter (Laran et al, 2022). The relative density estimated for common and/or striped dolphins in winter 2021 throughout the neritic shelf survey blocks of the Bay of Biscay is 0.92 individuals/km² (CV <21%; Laran et al, 2022). Digitally collected video footage during aerial surveys, which supplemented visual observations in the winter 2021, was used to confirm that common dolphins represent 96% of individual dolphins on those survey blocks. In the south of the IMMA the maximum density of common dolphins was encountered along the French coast during the autumn and winter (Authier et al., 2021; Laran et al., 2022a) and winter (Van Canneyt et al., 2023, 2020) with values of more than 1 ind/km² in winter. The fine-scale distribution of common dolphins and their overall densities increase over the winter period and peak in March–April. This trend was recently studied in relation to changes in oceanographic conditions to better understand the dolphins’ movements within coastal waters, and a strong preference for the coastal-shelf front was evident (Lambert et al, 2022a).
While in summer the distribution of the Atlantic harbour porpoise (Phocoena phocoena) peaked in Greater North Sea, a marked southward shift in summer distribution was observed between 1994 and 2005 (Geelhoed et al., 2022). Their uncorrected relative density was estimated to 0.042 ind.km² (CV=20%) in summer for the neritic portions of the IMMA in the summer of 2012 (Laran et al, 2017).
Harbour porpoises in the Irish and Celtic Seas and those in the Greater North Sea form separate populations from harbour porpoises on the Iberian Peninsula (NAMMCO, 2019). Winter density of harbour porpoises along the French coast (south of 48°North) was estimated to 0.031 ind.km² (CV=20%) in winter 2021 for the shelf block of the Bay of Biscay and 0.146 (CV=14%) for the English channel bock, with patches in west- and eastern part of the channel (relative densities uncorrected for bias, Laran et al, 2022a). Aerial surveys denote a high concentration of large groups of harbour porpoise aggregating in the south of the IMMA (Van Canneyt et al, 2023) with densities of more than 0.4 individuals/km², which was not visible from the previous wintering surveys in the area.
Criterion D: Special Attributes
Sub-criterion D2: Diversity
This IMMA contains habitat that supports an important diversity of cetacean species with 12 marine mammal species regularly occurring in the northern continental shelf of the Bay of Biscay. In addition to common dolphins and harbour porpoises, the Vulnerable North Atlantic fin whale (Balaenoptera physalus physalus) is regularly encountered during ship surveys in the area (Pelagis, 2021). Bottlenose dolphins (Tursiops truncatus, listed in annex II of the European Habitat directive), minke whales (Balaenoptera acutorostrata), Risso’s dolphins (Grampus griseus), Long-Finned pilot whales (Globicephala melas), Striped dolphins (Stenella coeruleoalba), Atlantic grey seals (Halichoerus grypus atlantica), Cuvier’s beaked whales (Ziphius cavirostris), Humpback whales (Megaptera novaeangliae) and pygmy and/or dwarf sperm whales (Kogia sp.) are regularly encountered (Gilles et al, 2023, Waggitt et al. 2020, Evans et al. 2021, Van Canneyt et al, 2020, 2023, ORCA, 2021).
Supporting Information
Authier, M., Blanchard, A., Dorémus, G., Genu, M., Laran, S., Nivière, M., Spitz, J., Van Canneyt, O., 2021. Suivi de la mégafaune marine au large des Pertuis charentais, de l’Estuaire de la Gironde et de Rochebonne par observation aérienne : Campagne SPEE-Rapport de campagne 2019-2020 – Rapport final. Observatoire Pelagis (UMS 3462, La Rochelle Université / CNRS) & Parc naturel marin de l’Estuaire de la Gironde et de la mer des Pertuis (Office Français de la Biodiversité).
Blanchard, A., Dorémus, G., Laran, S., Nivière, M., Sanchez, T., Spitz, J., and Van Canneyt, O. (2021) Distribution et abondance de la mégafaune marine en France métropolitaine. Rapport de campagne SAMM II Atlantique-Manche – Hiver 2021. https://www.observatoire-pelagis.cnrs.fr/wp-content/uploads/2021/10/SAMM_II_ATL-MAN_RapportCampagne_20210831.pdf
Borja, A., Amouroux, D., Anschutz, P., Gomez-Gesteira, M. , Uyarra, M.C. and Valdes, L. (2018). The Bay of Biscay. In: Sheppard, C., ed. World Seas: An Environmental Evaluation: 113-145
Evans, P.G.H., Carrington, C., and Waggitt, J. (2021) Risk Assessment of Bycatch of Protected Species in Fishing Activities. European Commission, Brussels. 213pp. https://ec.europa.eu/environment/nature/natura2000/marine/docs/RISK MAPPING REPORT.pdf
Geelhoed, S., Authier, M., Pigeault, R., Gilles, A., 2022. Abundance and Distribution of Cetaceans. In: OSPAR, 2023, OSPAR, 2023: The 2023 Quality Status Report for the Northeast Atlantic. OSPAR Commission, London (UK).
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Hammond, P.S., Lacey, C., Gilles, A., Viquerat, S., Börjesson, P., Herr, H., Macleod, K., Ridoux, V., Santos,M.B., Scheidat, M., Teilmann, J., Vingada, J. and Øien, N. 2017. Estimates of cetacean abundance in European Atlantic waters in summer 2016 from the SCANS-III aerial and shipboard surveys. WageningenMarine Research. https://library.wur.nl/WebQuery/wurpubs/fulltext/414756.
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Lambert, C., Pettex, E., Dorémus, G., Laran, S., Stéphan, E., Canneyt, O.V., and Ridoux, V. (2017) How does ocean seasonality drive habitat preferences of highly mobile top predators? Part II: The eastern North-Atlantic. Deep Sea Research Part II: Topical Studies in Oceanography 141, 133-154.
Lambert, C., Authier, M., Blanchard, A., Dorémus, G., Laran, S., Van Canneyt, O., and Spitz, J. (2022) Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution. Royal Society Open Science 9(11), 220379.
Laran, S., Genu, M., Authier, M., Blanchard, A., Dorémus, G., Sanchez, T., Spitz, J., Van Canneyt, O. (2022a) 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. https://www.observatoire-pelagis.cnrs.fr/wp-content/uploads/2022/09/RapportFinal_SAMM_20220719.pdf
Laran S., Blanchard A., Genu M., T. Sanchez, Dorémus G, Van Canneyt O. and Spitz J. (2022b). Suivi de la mégafaune marine au large des Pertuis charentais, de l’Estuaire de la Gironde et de Rochebonne par observation aérienne, Campagne SPEE 2019-2022. Rapport final. Observatoire Pelagis (UAR 3462, La Rochelle Université / CNRS) & Parc naturel marin de l’Estuaire de la Gironde et de la mer des Pertuis (Office Français de la Biodiversité). 146 pp. https://www.observatoire-pelagis.cnrs.fr/pelagis-2/les-programmes/spee/
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NAMCO (2019). North Atlantic Marine Mammal Commission and the Norwegian Institute of Marine Research.Report of Joint IMR/NAMMCO International Workshop on the Status of Harbour Porpoises in the North Atlantic. Tromsø, Norway. https://nammco.no/wp-content/uploads/2020/03/final-report_hpws_2018_rev2020.pdf
ORCA (2021). State of European Cetaceans. ORCA: Portsmouth. Available at: https://cdn2.assets-servd.host/orca-web/production/images/Our%20work/The%20State%20of%20Cetaceans/ORCA_The_State_of_European_Cetaceans_2021_Report.pdf
Pelagis (2021). Visual sightings of scientific surveys. https://pelabox.univ-lr.fr/pelagis/PelaObs/ Accessed 25th May 2023.
Peltier, H., Authier, M., Caurant, F., Dabin, W., Daniel, P., Dars, C., Demaret, F., Meheust, E., van Canneyt, O., Spitz, J., Ridoux, V., 2021. In the Wrong Place at the Wrong Time: Identifying Spatiotemporal Co-occurrence of Bycaught Common Dolphins and Fisheries in the Bay of Biscay (NE Atlantic) From 2010 to 2019. Front. Mar. Sci. 8. https://doi.org/10.3389/fmars.2021.617342
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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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