BIOTIC

BIOTIC Species Information for Semibalanus balanoides
All Taxonomy Biology Distribution Reproduction

Researched by	Nicola White	Data supplied by	MarLIN
Refereed by	Prof. Alan J. Southward
Distribution and Habitat
Distribution in Britain & Ireland	All coasts of Britain & Ireland, but sometimes is absent or rare in south-west Cornwall, the Isles of Scilly and south west Ireland.
Global distribution	Recorded in the north-east Atlantic from Spitsbergen to north-west Spain, on the Pacific coast of north America as far south as British Columbia and on the Atlantic coast as far south as Cape Hatteras; but missing from the Biscay coast of France.
Biogeographic range	Not researched	Depth range	Not relevant
Migratory	Non-migratory / Resident
Distribution Additional Information	In the 1950s the species was extremely rare in south-west Cornwall, and the far west of south County Cork (Crisp & Southward, 1958; Southward & Crisp, 1954; Southward, 1967). Since 1962, as sea temperatures decreased, its range spread westwards apparently from Lyme Bay (Southward, 1967). In 1998 it was found at Porthleven, although the population has declined recently (Southward, pers. comm.). Southward (1998) found that the record for the Azores by Nilsson-Cantell, in the Fauna of Scandinavia, was an error. Semibalanus balanoides is a boreo-arctic (i.e. northern) species. Its northern limits are closely paralleled by the summer limits of pack ice while its southern limits are controlled by high temperatures which prevent final maturation of gametes. The mean monthly sea temperature must fall below 7.2 °C in order for the barnacles to breed. Semibalanus balanoides is dominant in the eastern and northern regions of the British Isles. In the south west it gives way to chthamalid barnacles and it is sometimes absent or rare in south west Cornwall, south west Ireland and the Isles of Scilly. Semibalanus balanoides is less abundant on shores occupied by fucoid algae, because seaweeds prevent establishment of barnacle larvae or remove settled larvae by 'sweeping' across the rock (see reproduction). On shores exposed to strong wave action the upper limit of the barnacles distribution is raised because the shore is kept moist by spray. Semibalanus balanoides has a lower tolerance to desiccation than the chthamalid species due to a greater permeability of the shell plates. It is sometimes found sublittorally.

Substratum preferences	Bedrock Large to very large boulders Small boulders Cobbles Pebbles Artificial (e.g. metal/wood/concrete)	Physiographic preferences	Strait / sound Sealoch Ria / Voe Estuary Open coast
Biological zone	Upper Eulittoral Mid Eulittoral Lower Eulittoral	Wave exposure	Extremely Exposed Very Exposed Exposed Moderately Exposed Sheltered Very Sheltered Extremely Sheltered Ultra Sheltered
Tidal stream strength/Water flow	Very Strong (>6 kn) Strong (3-6 kn) Moderately Strong (1-3 kn) Weak (<1 kn)	Salinity	Reduced (18-30 psu) Full (30-40 psu) Variable (18-40 psu)
Habitat Preferences Additional Information
Distribution References	Rainbow, 1984, Bennell, 1981, Barnes, 1953, King et al., 1993, Stubbings, 1975, Barnes, 1958, Barnes et al., 1963, Lewis, 1964, Bassindale, 1964, Jenkins et al., 2000, Southward et al., 1995, Hawkins & Hartnoll, 1982, Crisp & Southward, 1958, Southward & Crisp, 1954, Southward, 1967, Southward, 1998,