A rare, rather small soft coral that occurs in small colonies in rocky clefts, gullies and wrecks. Only one location is recorded in Northern Ireland.

In brief

• Only known Northern Ireland site is the west end of Rathlin Island
• Habitat — rocky overhangs, caves, gullies and wrecks
• Can be seen throughout the year
• This is a species of conservation concern because of its rarity, and localised nature of its colonies
• Rarity is the main concern, but the very localised nature of its larval dispersal means colonies are unlikely to recover from any disruption.

Species description: Alcyonium hibernicum is a small soft coral occurring in very localised situations. Its ‘fingers’ are up to 40mm tall, pink with whitish flecks on the tentacles, giving a somewhat spangled appearance. The species has undergone a number of taxonomic reviews and synonyms include Parerythropodium coralloides, Alcyonium coralloides, and Alcyonium pusillum, and readers should investigate these as well when researching distribution and other data.

Life cycle: The species only has female colonies, and through July the ova develop parthenogenically, that is, without fertilisation, and are brooded in the gastric cavity. The larvae are released in August and settle on the benthos, very close to the parental colony. As a result distribution is very localised, and colonies within a small area are likely to be genetically very similar, and there is reduced chance of dispersal and colonisation of new areas of sea bed compared with its close relative A. digitatum.

Similar species: Alcyonium digitatum — dead man’s fingers. This is a larger and much more common species, widely occurring in more open subtidal rock and boulder situations dominated by tidal currents. It ranges from white through yellow to orange, and lacks the spangled effect seen in hibernicum.

How to see this species: The species has only been recorded in Northern Ireland at Farganlack Point on the west end of Rathlin Island, and in Ireland in south-west of Campbell’s Bed in Mulroy Bay and in Lough Hyne. Elsewhere, it has been recorded off western Scotland, the Calf of Man, the Pembrokeshire and Cornish coasts. Most likely locations are rocky sites down to about 35m depth, with little algal growth, under overhangs, in caves, gullies and crevices, and on wrecks. It has been recorded in enclosed locations like sea loughs where salinity is slightly reduced.

Current status: Only one location recorded in Northern Ireland. The species has no legal protection.

Why is this species a priority in Northern Ireland? Alcyonium hibernicum is extremely scarce, and Northern Ireland probably holds 50 per cent of the Irish population. Its method of reproduction and especially the localised nature of its colonies mean that they would be unlikely to recover following any significant damage or disruption.

Threats: No immediate threats known.

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

iNaturalist: Alcyonium hibernicum at iNaturalist World Species Observations database.

WoRMS: Alcyonium hibernicum at World Register of Marine Species. Accepted name: Alcyonium hibernicum (Renouf, 1931). AphiaID: 178914.

Classification: Biota; Animalia; Cnidaria; Anthozoa; Octocorallia; Malacalcyonacea; Alcyoniidae; Alcyonium