Biodiversity & Conservation

Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment.



Image Rohan Holt - Halidrys on flat pebbles and gravel. Image width ca 1 m.
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Distribution map

IR.MIR.SedK.HalXK recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Marine natural heritage importance

Listed under EC Habitats Directive
National importance Not available
Habitat Directive feature (Annex 1) Reefs
Large shallow inlets and bays

Biotope importance

The interstices between understorey macroalgae may act as shelter or refuge for larvae and juveniles of the organisms found in the community (Birkett et al., 1998). Laboratory evidence (Johns & Mann, 1987) suggested that Irish moss (Chondrus crispus) and habitat complexity attract juvenile lobster, presumably as a refuge from predation. However, Vadas & Elner (1992) suggested that field evidence for large invertebrates or fish using macroalgal habitats as refuges or nurseries was conjectural. Nesting fish, such as corkwing wrasse (Crenilabrus melops) construct nests of seaweeds in crevices and between rocks, and may therefore, use the biotope for nesting purposes, although no evidence was found to this effect.


None of the species within the biotope are known to be exploited presently. However, Chondrus crispus, Furcellaria lumbricalis and Ahnfeltia plicata are subject to exploitation in Europe and Canada (see individual species reviews).

Additional information icon Additional information

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This review can be cited as follows:

Tyler-Walters, H. 2002. Halidrys siliquosa and mixed kelps on tide-swept infralittoral rock with coarse sediment.. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>