Biodiversity & Conservation

Overhangs and caves



Image Keith Hiscock - A well developed overhang community with pendulous polyclinid tunicates. Image width ca 1 m.
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Distribution map

LR.FLR.CvOv recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland Present on rocky coasts all around Britain and Ireland.
National importance Scarce

Text page icon Description of biotope

For a full description of this biotope including characterizing species, distribution, survey information and references visit JNCC

Where overhangs occur on rocky shores there is a reduction in desiccation which allows certain species to proliferate, in particular, crusts of bryozoans (for example, Umbonula littoralis), sponges (such as Halichondria panicea and Hymeniacidon perleve), ascidians (such as Botryllus schlosseri), barnacles (Balanus perforatus in the south-west) and spirorbid tubeworms (SLR.SByAs). Erect bryozoans may occur such as species of Scrupocellaria and Bugula sp. Pendulous species such as the ascidian Morchellium argus and the fleshy bryozoan Alcyonidium diaphanum may also occur. Shade-tolerant red seaweeds can also grow in such conditions (SLR.SR). Mobile species that occur include the painted top shell Calliostoma zizyphinum, the cowrie, Trivia spp., the sting winkle Ocenebra erinacea and the cushion star Asterina gibbosa. On shady overhangs on the lowest shore, branching sponges such as Stelligera stuposa and corals (Caryophyllia smithii and sometimes Balanophyllia regia) may be found together with a range of sea anemone species. Adapted from Connor et al. (1997a).

Additional information icon Additional information


This review can be cited as follows:

Hiscock, K. 2002. Overhangs and caves. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/11/2015]. Available from: <>