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ISRA FACTSHEETS

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ISRA FACTSHEETS

EUROPEAN ATLANTIC

Calf of Man – Orrisdale ISRA

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Calf of Man – Orrisdale ISRA

Calf of Man – Orrisdale

Summary

Calf of Man – Orrisdale is located on the west coast of the Isle of Man, a self-governing British Crown Dependency. The area is situated within the Irish Sea, between Ireland and the United Kingdom of Great Britain and Northern Ireland. The area is characterised by sandy and muddy substrates. It is influenced by frontal systems and eddies. Within this area there are: threatened species and undefined aggregations (Basking Shark Cetorhinus maximus).

Calf of Man - Orrisdale

Calf of Man – Orrisdale

DESCRIPTION OF HABITAT

Calf of Man – Orrisdale is located on the west coast of the Isle of Man, a self-governing British Crown Dependency. It is situated within the Irish Sea, between Ireland and the United Kingdom of Great Britain and Northern Ireland. The area is characterised by fine sediments, including muddy and sandy substrates.

The area is influenced by a range of oceanographic features, including frontal systems and eddies, that result in it being an area of relatively high productivity (Holt et al. 2004; Gowen & Stewart 2005). The main currents move northwards from the Celtic Sea through St George’s Channel, through this area, and then to the North Channel.

This Important Shark and Ray Area is pelagic and is delineated from inshore and surface waters (0 m) to 110 m based on the bathymetry of the area.

CRITERION A

VULNERABILITY

One Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occurs in the area. This is the Endangered Basking Shark (Rigby et al. 2021).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Calf of Man – Orrisdale is an important area for undefined aggregations of one shark species.

Opportunistic land-based and vessel-based Basking Shark sightings reported by citizen scientists are collated into a dedicated database (Shark Trust unpubl. data 2025). Observations of three or more Basking Sharks reported at one time were extracted, and duplicate records were removed. Between 2010–2023, a total of 1,161 Basking Sharks were observed from 213 aggregations in the area (Shark Trust unpubl. data 2025). The average number of aggregations per year in this period was 13, with an average of 6 individuals (maximum = 20 individuals) per aggregation. Aggregations have been reported from this area in 2010 (n = 100 aggregations; 535 individuals), 2011 (n = 46 aggregations; 270 individuals), 2012 (n = 30 aggregations; 140 individuals), 2013 (n = 12 aggregations; 67 individuals), 2015 (n = 17 aggregations; 107 individuals), 2016 (n = 6 aggregations; 36 individuals), and 2023 (n = 2 aggregation; 6 individuals). This area has the highest number of contemporary known citizen science reports of Basking Shark aggregations within the Isle of Man territorial waters, and some of the largest numbers compared to adjacent areas. Basking Sharks may be aggregating in this area for feeding purposes based on direct observations of feeding behaviour from citizen scientists (Shark Trust unpubl. data 2025). Between 2010–2023, feeding behaviour was recorded for 24 aggregations (n = 98 individuals). Further information is required to determine the nature and function of these aggregations.

Calf of Man - Orrisdale

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