Biscay Shelf Edge and Slope IMMA
Size in Square Kilometres
70,042 km2
Qualifying Species and Criteria
Sperm whale – Physeter macrocephalus
Criterion A, B (2)
Fin whale – Balaenoptera physalus
Criterion A, B (2)
Blue whale – Balaenoptera musculus
Criterion A
Sei whale – Balaenoptera borealis
Criterion A
Common bottlenose dolphin – Tursiops truncatus
Criterion B (2)
Striped dolphin – Stenella coeruleoalba
Criterion B (2)
Long-finned pilot whale – Globicephala melas
Criterion B (2)
Common dolphin – Delphinus delphis
Criterion B (2)
Marine Mammal Diversity
Criterion D (2)
Stenella coeruleoalba, Delphinus delphis, Tursiops truncatus, Physeter macrocephalus, Balaenoptera musculus, Balaenoptera physalus, Balaenoptera borealis, Phocoena phocoena, Grampus griseus, Globicephala melas, Globicephala macrorhynchus, Orcinus orca, Ziphius cavirostris, Balaenoptera acutorostrata
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Summary
The Biscay shelf edge and slope is characterised by a continental slope where the seafloor descends from 200m to over 4,000m depth over a short distance, and is punctuated by many submarine canyons and other topographic features, that then give way to the abyssal plain. The oceanic processes and bathymetry in this area drive productivity and create diverse habitats for at least 14 regularly occurring cetacean species, each with distinct habitat preferences. Of particular interest are the large aggregations of common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), common bottlenose dolphins (Tursiops truncatus), long-finned pilot whales (Globicephala melas), fin whales (Balaenoptera physalus) and sperm whales (Physeter macrocephalus).
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
This candidate IMMA provides habitat for fin whales (Balaenoptera physalus), which are listed as Vulnerable on the IUCN Red List of Threatened Species (Cooke, 2018a).
The area also provides habitat for sperm whales (Physeter macrocephalus), which are listed as Vulnerable on the IUCN Red List (Taylor et al. 2019).
Sei whales (Balaenoptera borealis) are regularly observed in this area, and they are listed as Endangered on the IUCN Red List (Cooke, 2018b).
Blue whales (Balaenoptera musculus) have also been recorded in this area (James Cook survey in August and September 2015). The blue whale is listed as endangered on the IUCN Red List (Cooke 2018c), and population estimates for the species in the North Atlantic range from 250 adults (DFO, no date) to 1000 individuals (Pike et al. 2009).
Criterion B: Distribution and Abundance
Sub-criterion B2: Aggregations
The continental shelf edge and slope in the Bay of Biscay has underlying qualities that support concentrations of a variety of cetacean species well described by various large scale dedicated surveys, such as SCANS II,III, IV (Hammond et al. 2021, Lacey et al. 2022, Gilles et al, 2023) and the large aerial survey SAMM (Suivi Aérien de la Mégafaune Marine, Aerial Census of Marine Megafauna) (Laran et al, 2017, 2022).
A recent OSPAR assessment (Geelhoed et al, 2023) and the compilation of a complex data set (Waggitt et al. 2020) including aerial/vessel platforms, revealed high densities of common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), common bottlenose dolphins (Tursiops truncatus), long-finned pilot whales (Globicephala melas), sperm whales and fin whales in this IMMA.
The SAMM over the Bay of Biscay and English Channel conducted in winter 2011–2012 and summer 2012, detected high densities of common dolphins on the shelf during winter months and a movement to the shelf edge, slope and oceanic areas during the summer (Laran et al. 2017, Blanchard et al. 2021, Laran et al. 2022).
High densities of striped dolphins have also been recorded in this area (Certain et al. 2008). Long-term citizen science surveys from platforms of opportunity in the Bay of Biscay (2006-2022) have also recorded consistent sightings and higher encounter rates along the shelf edge and slope in all months surveyed (March to October, with 0.003 sightings/km within the proposed area vs 0.002 sightings/km in the neighbouring areas) (ORCA, unpublished data).
Griffiths (2015) analysed ten years of survey data, collected from platforms of opportunity crossing both the English Channel and Bay of Biscay, and predicted greater abundance of common bottlenose dolphins along and over the continental shelf edge (Geelhoed et al, 2022). Certain et al. (2008) linked the high density of common bottlenose dolphins at the shelf edge to the availability of fish prey. Long-term citizen science surveys from platforms of opportunity in the Bay of Biscay (2006-2022) recorded encounter rates of 0.001 sightings/km within the IMMA vs 0.0008 sightings/km outside the proposed area along the shelf edge and slope for common bottlenose dolphins (ORCA, unpublished data).
Dedicated aerial and boat-based surveys have also shown that long-finned pilot whales have a strong preference for the continental shelf edge and slope (as is typical for the species) with evidence for both summer (Geelhoed et al. 2023, Waggitt et al. 2020, Pelagis, 2021) and winter presence in the area (Blanchard et al. 202, Laran et al 2017). Data analysed from citizen science surveys from platforms of opportunity yield a long-finned pilot whale encounter rate of 0.002 sightings/km within the IMMA compared to 0.0006 sightings/km outside the IMMA (ORCA, unpublished data).
Fin whales have also been consistently observed along the continental shelf edge and on the slope in Biscay (Waggitt et al. 2020, Pelagis, 2021; Hammond et al. 2021, Lacey et al. 2022, ORCA unpublished data). Habitat modelling studies suggest that the slope supports high densities of fin whales, with habitat suitability peaking around the 2,000m isobath (Garcia-Baron et al. 2018). SAMM surveys conducted in winter 2011–2012 and summer 2012 also reported that fin whales were frequently sighted in waters 2,000m deep with an oceanic distribution in the summer. Fin whale density on the slope was estimated as 0.002 individual/km² (CV=65%; corrected for availability bias) in summer and decreased in winter (Laran et al. 2017).
Sperm whales are distributed throughout the deep waters of the Bay of Biscay with high densities along the slope from April to December (Waggitt et al. 2020). SAMM surveys estimated sperm whale densities as 0.005 individual/km² (CV=69%; corrected for availability bias) in summer along the Biscay slope strata and decreased in winter (Laran et al. 2017).
Criterion D: Special Attributes
Sub-criterion D2: Diversity
The continental shelf edge and slope in the Bay of Biscay offers varied topography and a wide range of habitats that supports multiple cetacean species with distinct habitat preferences (Kiszka et al. 2007, Borja et al. 2018). At least 14 different species of cetacean regularly occur in this area, ranging from small dolphin species to large baleen whales and deep divers (Pelagis, 2021, Matear et al. 2019, Waggitt et al. 2020, ORCA unpublished data).
Of particular interest are the large aggregations of several dolphin species, specifically common dolphins, striped dolphins, common bottlenose dolphins and long-finned pilot whales, as well as sperm whales, beaked whales and fin whales. Bathymetry has been identified as a key factor influencing species distribution and habitat preferences of toothed cetaceans within the Bay of Biscay (Kiszka et al. 2007). Sperm whales are sighted on the shelf edge and slope area (Waggitt et al. 2020, Pelagis, 2021), along with beaked whales, particularly Cuvier’s beaked whales (Ziphius cavirostris) (Pelagis, 2021). Baleen whales are also sighted regularly on the slope, but in particular, fin whales are sighted frequently in waters 2,000m deep. Common minke whales are seen in the winter (Blanchard et al. 2021, Pelagis, 2021, Laran et al. 2017).
Supporting Information
Amaro, T., Huvenne, V.A.I., Allcock, A.L., Aslam, T., Davies, J.S., Danovaro, R., De Stigter, H.C., Duineveld, G.C.A., Gambi, C., Gooday, A.J., Gunton, L.M., Hall, R., Howell, K.L., Ingels, J., Kiriakoulakis, K., Kershaw, C.E., Lavaleye, M.S.S., Robert, K., Stewart, H., Van Rooij, D., White, M., Wilson, A.M. (2016). The Whittard Canyon – A case study of submarine canyon processes, Progress in Oceanography, 146: 38-57
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
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Certain, G., Ridoux, V., van Canneyt, O. and Bretagnolle, V. (2008). Delphinid spatial distribution and abundance estimates over the shelf of the Bay of Biscay. ICES Journal of Marine Science 65(4): 656-666
Cooke, J.G. (2018a). Balaenoptera physalus. The IUCN Red List of Threatened Species 2018: e.T2478A50349982. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T2478A50349982.en. Accessed on 11 April 2023
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Geelhoed, S., M. Authier, R. Pigeault, et A. Gilles. 2023. Abundance and Distribution of Cetaceans. In: OSPAR, 2023. OSPAR, 2023: The 2023 Quality Status Report for the Northeast Atlantic. London (UK): OSPAR Commission, 2022. https://oap.ospar.org/en/ospar-assessments/quality-status-reports/qsr-2023/indicator-assessments/abundance-distribution-cetaceans/.
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