BIOTIC

BIOTIC Species Information for Chthamalus stellatus
All Taxonomy Biology Distribution Reproduction

Researched by	Karen Riley	Data supplied by	MarLIN
Refereed by	Prof. Alan J. Southward
Distribution and Habitat
Distribution in Britain & Ireland	A southern, warm-water species recorded on the south and west coasts of the British Isles as far north as the Shetland Isles. The species is less abundant along the channel towards The Isle of Wight, its eastern limit.
Global distribution	Occurs in The Black Sea, along most of the Mediterranean coast, and further south in Tunisia, Madeira, the Azores, and Cape Verde Islands. No recorded exist further south of this point.
Biogeographic range	Not researched	Depth range	Mid to lower eulittoral
Migratory	Non-migratory / Resident
Distribution Additional Information	Geographical distribution Crisp et al. (1981) described the distribution of Chthamalus stellatus and Chthamalus montagui. Chthamalus stellatus is abundant along western coasts of Britain and Ireland. It does not occur in the central Irish Sea. It occurs in northern and north-eastern Scotland including at exposed locations in Shetland.. In France it is abundant westwards from Roscoff, is absent from the Bay of St. Malo, and is less common east of Roscoff. Chthamalus stellatus occurs along Irish coasts from Antrim around to Wexford, although it only occurs in abundance along the west coast. The species is less abundant along the channel towards the Isle of Wight, its eastern limit. Individuals recorded as Chthamalus stellatus in the Indian and Pacific Ocean are, in fact, other species of the stellatus group. Vertical zonation Chthamalus stellatus is dominant over Chthamalus montagui at exposed sites (Southward, 1976; Crisp et al., 1981). Where the species overlap, Chthamalus montagui has a greater vertical distribution, extending above and below that of Chthamalus stellatus (Burrows et al., 1992) and, while Chthamalus montagui is more common between MHWS & MHWN, Chthamalus stellatus is abundant lower down at MTL and below (Pannacciulli & Relini, 2000). Chthamalus stellatus inhabits the lower half of the intertidal, but in wave-exposed or wet and shady places they occur higher up on shore (Crisp et al., 1981; Pannacciulli & Relini, 2000). Physical factors such as exposure to seawater, desiccation and poor food supply limit the distribution of barnacles on the upper shore, whereas competition for space, predation and strong wave action limit the distribution at low and mid shore levels (Pannacciulli & Relini, 2000). The higher the species occurs up on the shore, the more resistant to desiccation influences they tend to be (Southward, 1955). The distribution of Chthamalus spp. is not affected by small increases in algal cover. Hawkins & Hartnoll (1982) found that the lower shore level limit was controlled by the presence of algal turf. However, rapid increases to 100 % algal cover can lead to a massive decline in barnacle populations to almost zero in a year or two (Southward, 1991). Substratum preference Barnacles attach themselves to hard, rough surfaces and are rarely found on chalk cliffs (Moore & Kitching, 1939). Moore & Kitching (1939) also suggested that this may be because the surface is smooth, washed away easily, or too porous (making it possible to be dried out from below). Temperature dependence / competition Chthamalus spp. prefer warm temperatures, whereas Semibalanus balanoides prefers low temperatures. This is reflected by the changes in their distribution with changes in climate. For example, in the severe winter of 1962-63 Chthamalus populations declined (Southward, 1967) while Semibalanus balanoides increased, and in the temperature rise of 1988-89 the trend was reversed (Southward, 1991). Long term trends are also evident. A decline in Chthamalus populations and an increase in Semibalanus balanoides occurred between 1962 and 1980, corresponding with a decrease in sea temperatures (Southward, 1991). Since 1980 there has been a general increase in Chthamalus spp. (Southward, 1991), maybe corresponding with gradual climate warming. Southward & Crisp (1954) noted that in 1948-51, during high temperatures in the British Isles Chthamalus spp. dominated over Semibalanus balanoides, and from 1952, during lower temperatures there was a resurgence of Semibalanus balanoides. Southward (1991) noted a two year phase lag between temperature trends and changes in barnacle abundance in Plymouth. Chthamalus spp. are more abundant in waters where the mean temperatures are above 10 °C for several months of the year (Southward, 1955).

Substratum preferences	Bedrock Large to very large boulders Artificial (e.g. metal/wood/concrete)	Physiographic preferences	Open coast
Biological zone	Mid Eulittoral Lower Eulittoral	Wave exposure	Exposed
Tidal stream strength/Water flow	Very Strong (>6 kn) Strong (3-6 kn) Moderately Strong (1-3 kn)	Salinity	Full (30-40 psu)
Habitat Preferences Additional Information
Distribution References	Burrows et al., 1992, Hayward & Ryland, 1995b, Hayward et al., 1996, Moore & Kitching, 1939, Southward, 1976, Pannacciulli & Relini, 2000, Southward, 1955, Southward, 1991, Southward, 1967, Crisp et al., 1981, Southward & Crisp, 1954, Barnes, 1953, Barnes et al., 1963, Bassindale, 1964, Hawkins & Hartnoll, 1982, Bassindale, 1964,