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ISRA FACTSHEETS

EUROPEAN ATLANTIC

ISRA FACTSHEETS

EUROPEAN ATLANTIC

João Valente Shelf ISRA

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João Valente Shelf ISRA

João Valente Shelf

Summary

João Valente Shelf is located between Maio and Boa Vista islands, Cabo Verde. The area encompasses a mixture of hard and sandy substrates on a wide shelf. The large-scale surface circulation in the area is characterised by the presence of cyclonic and anticyclonic eddies Within this area there are: range-restricted species (Cape Verde Skate Raja herwigi).

João Valente Shelf

João Valente Shelf

DESCRIPTION OF HABITAT

João Valente Shelf is located between Maio and Boa Vista islands, Cabo Verde. The area encompasses a mixture of hard and sandy substrates on a wide shelf of ~100 m depth that rises from 1,000 m, with the peak 10 m below the surface, known as João Valente Bank. The shelf is relatively flat and sandy, and unobstructed to a depth of 100 m. Deeper than this it becomes very steep and rough (Krakstad et al. 2011).

This region lies within the transition zone where South Atlantic Central Water and North Atlantic Central Water mix, occupying the upper layers of the water column (Michalsen 2022). The large-scale surface circulation in the area is influenced by seasonal wind variability and the movement of the Intertropical Convergence Zone. These factors drive seasonal changes in the flow field, which is characterised by the presence of cyclonic and anticyclonic eddies (Michalsen 2022).

This Important Shark and Ray Area is benthic and subsurface and is delineated from 55–380 m based on the depth range of Qualifying Species globally.

CRITERION B

RANGE RESTRICTED

This area holds the regular presence of the Cape Verde Skate as a resident range-restricted species.

Scientific surveys using benthic trawls were carried out in 2011 and 2021 across Cabo Verdean waters. Of the 59 Cape Verde Skate captured during these surveys, 33 (55.9%) were from within this area at a depth of 61–208 m. In 2011, 30 surveys were conducted at depths of 31–909 m, with eight of them (26.7%) occurring within this area (51–208 m depth) (Krakstad et al. 2011). A total of 35 Cape Verde Skates were captured in 2011, with 13 (37.1%) from this area (70–82 m depth; Michalsen 2022). In 2021, 27 surveys were conducted, six of which (22.2%) were in this area (Michalsen et al. 2022). A total of 24 Cape Verde Skates were captured, with 20 (83%) coming from this area (70–176 m depth; Michalsen 2022). In addition to these 59 individuals captured during the 2011 and 2021 surveys, only eight other specimens have been historically documented (Krefft 1965; Stehmann 1971). Cape Verde Skates captured within this area represent 49.3% of the total number of individuals known to be captured for this species (n = 67), despite sampling efforts in adjacent areas over the years, highlighting the importance of this area. The Cape Verde Skate is endemic to Cabo Verde and its distribution falls outside Large Marine Ecosystems.

João Valente Shelf

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