true

ISRA FACTSHEETS

EUROPEAN ATLANTIC

ISRA FACTSHEETS

EUROPEAN ATLANTIC

Inner Hebrides ISRA

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Inner Hebrides ISRA

Inner Hebrides

Summary

Inner Hebrides is located in the northern Sea of Hebrides on the west coast of Scotland, United Kingdom of Great Britain and Northern Ireland. It is situated west of the Isle of Mull and south of the Isle of Skye. The area encompasses the surrounding waters of the Isles of Coll, Tiree, Rum, Eigg, Muck, Canna, and Hyskeir. The habitat is characterised by sandy and rocky substrates. It is influenced by the Scottish Coastal Current. Within this area there are: threatened species (e.g., Tope Galeorhinus galeus); and undefined aggregations (e.g., Basking Shark Cetorhinus maximus).

Inner Hebrides

Inner Hebrides

DESCRIPTION OF HABITAT

Inner Hebrides is located in the northern Sea of Hebrides on the west coast of Scotland in the United Kingdom of Great Britain and Northern Ireland. It is situated west of the Isle of Mull and south of the Isle of Skye. The area encompasses the waters around the Isles of Coll, Tiree, Rum, Eigg, Muck, Canna, and Hyskeir. The habitat is characterised by sandy and rocky substrates (Moore & Wilson 2002). It is influenced by the Scottish Coastal Current (Inall et al. 2009), with the variation in phytoplankton being a driver of productivity in the area (Fehling et al. 2012).

This Important Shark and Ray Area is benthic and pelagic and is delineated from inshore and surface waters (0 m) to 114 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

Two Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occur in the area. These are the Critically Endangered Tope (Walker et. al. 2020) and the Endangered Basking Shark (Rigby et al. 2021).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Inner Hebrides is an important area for undefined aggregations of two shark species.

Opportunistic land-based and vessel-based sightings reported by citizen scientists to the Shark Trust’s Basking Shark Project are collated into a dedicated database, with records since 1987 (Shark Trust unpubl. data 2025). Observations of three or more individuals reported at one time were extracted, and duplicate records were removed. Between 2010–2019, a total of 5,210Basking Sharks were observed from 392 aggregations (Shark Trust unpubl. data 2025). The mean number of aggregations per year in this period was 25 (maximum of 301 individuals in one aggregation), with 326 individuals sighted per year on average. Aggregations have been reported from this area in 2010 (n = 99 aggregations; 1,445 individuals), 2011 (n = 53 aggregations; 742 individuals), 2012 (n = 70 aggregations; 1,452 individuals), 2013 (n = 83 aggregations; 962 individuals), 2014 (n = 11 aggregations; 82 individuals), 2015 (n = 49 aggregations; 322 individuals), 2016 (n = 17 aggregations; 136 individuals), 2017 (n = 3 aggregations; 11 individuals), 2018 (n = 5 aggregations; 40 individuals), 2019 (n = 1 aggregation; 9 individuals), and 2025 (n = 1 aggregation; 9 individuals). Additional aggregations in this area are indicated through tagging and tracking data, and underwater footage (Witt et al. 2019). This is one of the locations in the United Kingdom of Great Britain and Northern Ireland with the highest number of contemporary known citizen science reports of Basking Shark aggregations. This species may be aggregating in this area for feeding purposes based on direct observations by citizen scientists of animals feeding at the surface (Shark Trust unpubl. data 2025). Further information is required to understand the nature and function of these aggregations.

Tope aggregate in groups of more than one thousand individuals in Vaul Bay off Tiree Island in this area. A citizen scientist visits the island for two weeks per year (P Stewart & J Thorburn unpubl. data 2025). Annual citizen science drone footage (~20 minutes per flight) has observed large aggregations in 2018, 2019, 2021, 2022, 2023, and 2024. Higher resolution data are available for recent survey years when Tope aggregations were observed on four days in each of 2021, 2022, and 2023. A dedicated research trip in 2024, where Tope were caught via rod-and-line, confirmed species presence (J Thorburn unpubl. data 2025). These aggregations represent the largest demonstrated aggregation of this species within the United Kingdom of Great Britain of Northern Ireland, and adjacent jurisdictions including Ireland. Further information is required to understand the nature and function of these aggregations.

Inner Hebrides

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