A large sponge, dwelling in relatively deep water, known only from two general locations in Northern Ireland, and thought to have suffered a decline.

In brief

• Found off Rathlin Island and off the Maidens
• Rock in depths of 40m or deeper
• Can be found throughout the year
• Northern Ireland holds an important proportion of this species
• Main threats / cause of decline are not known.

Species description: Clathria barleei is a large sponge, up to 20cm in height and across base, coloured a dull beige, yellow or green. It has a relatively flat profile, and a porous, rather pitted appearance. There is a variety of spicules, or skeletal structures, in the body structure; some are pin-shaped, curved or straight, some have flanges, others straight but with a notable kink midway along the length.

Life cycle: Sponges have either separate sexes or are hermaphrodite. In the case of the latter, self-fertilisation is avoided by eggs and sperms maturing at different rates within the same individual, so when spawning takes place and sperms are released through exhalent openings, it is unlikely that the eggs will be fertilised. Alternatively, the eggs are retained within the sponge, and sperms drawn in from surrounding water. Fertilised eggs are released and develop into planktonic larvae. Asexual reproduction may also be achieved by budding, whereby a small unit of the sponge separates and develops as an independent entity.

Similar species: There are four synonyms, largely as a result of confusion caused by the variety of spicule types - detailed confirmation of identity can only be achieved by examination of these.

How to see this species: This sponge can be found in Northern Ireland at the south-east end of Rathlin Island and at five sites in the vicinity of the Maidens; however, it is often beyond the range of most divers, generally occurring from 40m to depths in excess of 100m, on rocks, boulders and stones. In Ireland it has been recorded from south Donegal Bay, Achill Island, the Aran Islands, and the outer Kenmare River. Further afield, its distribution extends from the Arctic through to western coast of France and includes Rockall and Mull.

Current status: Known from only six sites in Northern Ireland. The species has no legal protection.

Why is this species a priority in Northern Ireland? The species is rare, and is regarded as being in decline. It is also considered scarce in Britain and Ireland. Northern Ireland holds over 50 per cent of the locations in Ireland.

Threats: No threats or issues causing the suspected decline have been identified.

Action:

• Maintain the number of viable populations
• Maintain the range
• Establish appropriate management on appropriate historical sites
• Consider protective measures for the Maidens locations.

Objectives: Records of new sites for this species, with details of habitat and population are always valuable. Send these to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257 or e-mail cedar.info [at] nmni.com. If you are a diver, and interested in becoming involved in recording marine life in Northern Ireland through the Seasearch project, contact Claire Goodwin at claire.goodwin [at] gmail.com or look at the web site www.seasearch.org.uk (Northern Ireland web pages).

Conservation: Survey work is being conducted throughout Northern Ireland waters (including the north coast) by Northern Ireland Environment Agency for this and other species and habitats generally.

Rathlin Island has been designated a Special Area for Conservation under the EU Habitats Directive.

There is no Species Action Plan for Clathria barleei; however, the UK Habitat Action Plan for Inshore Sublittoral Rock contains the following provision:

• maintain the extent and quality of inshore sublittoral rock habitats in the UK, including the full diversity of communities.

Measures to be considered further include:

• protecting sites of conservation importance from damage through contamination and physical disturbance (for example, turbidity and towed fishing gear)
• requiring EIAs for coastal developments to examine potential effects on intertidal and nearshore areas
• monitoring any impact of dump sites on inshore sublittoral rock habitats, communities and wildlife, and taking action as appropriate
• implementing strategies for managing the coastal zone at local, regional and national levels.

Distribution Map from NBN: Clathria barleei at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Clathria barleei at iNaturalist World Species Observations database.

WoRMS: Clathria barleei at World Register of Marine Species. Accepted name: Clathria (Clathria) barleei (Bowerbank, 1866). AphiaID: 167498.

Literature:

Picton, B.E., Morrow, C.C. and van Soest, R.W.B. (2007). [In] Sponges of Britain and Ireland. http://www.habitas.org.uk/marinelife/sponges.asp?item=C7920.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Poecilosclerida; Microcionidae; Microcioninae; Clathria

Previous species

Next species

Allen & Mellon Environmental Ltd. (2026). Clathria barleei. (Bowerbank, 1866). [In] Priority species, Marine Biodiversity Portal NI. https://www2.habitas.org.uk/marbiop-ni/priorityaccounts.php?item=C7920. Accessed on 2026-07-28