Site details

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2 stars - De facto protected because of geographical conditions and location
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Type diagram of Les Ridens. Photo: D Menu in Davoult & Richard, 1988

Synoptic description of site:

Rocky shallow of the center of the Eastern Channel. Mixing of hard substrata and clean sand and gravel community. Occurrence of several species reaching their northern limit in the Channel. 270 species recorded.

Extensive description of site:

Les Ridens is a large rocky shallow area in the center of the Eastern Channel, characterized by a mixing of hard substrata and clean heterogeneous sands and gravel. It is located in an area of low difference between summer and winter water temperatures (<10°C).

Habitats present:
Sublittoral XX
Seagrass beds 

Description of fauna and flora:

The fauna is exceptional for the region, several species reach their Northern limit here in the Channel. 270 species have been recorded. There is an important border effect between the fauna of circalittoral rocks (up to 15 m depth) and of heterogeneous sands and gravel (down to 30 m depth).

Pristiness: High


The presence of rocks avoid the pressure by fishing. The "Ridens" are located in an area caracterized by a small difference between summer and winter temperatures (dt = 10°C)

Human impact:

The area is subjected to low level of pollution owing to its offshore location. The presence of rocks prevents the pressure by fishing activities.


All facilities for marine biodiversity research are available: research vessels, scientific divers, fully equipped laboratories and accommodation at the Marine Station of Wimereux.

Available database and website:

The global species inventory ("Faune et Flore du littoral du Pas de Calais et de la Manche Orientale") is currently updated, and is available as hard copy and will be soon available on-line on the website of the Marine Station. The inventory of benthic macrofauna and flora of Les Ridens is only available as hard copy.

Commitment and ongoing research:

The Marine Station, the "Unite Mixte de Recherche ELICO" from CNRS and the Lille 1 University are all based in Wimereux and undertake biodiversity-related research in the area in collaboration with the Biological Station of Roscoff for this project.