BIOTIC

BIOTIC Species Information for Chthamalus montagui
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 warm-water species recorded on the south and west coasts of Britain as far north as Orkney and along the Scottish east coast south to Aberdeen. The Isle of Wight is its eastern limit in the English Channel. It is relatively abundant on Irish coasts.
Global distribution	Crisp et al. (1981) noted that its distribution extends through the western and eastern Mediterranean and down the north African coast to Mauritania.
Biogeographic range	Not researched	Depth range	Not relevant
Migratory	Non-migratory / Resident
Distribution Additional Information	Geographical distribution Crisp et al. (1981) have described the distribution of Chthamalus stellatus and Chthamalus montagui. Chthamalus montagui occurs all around the western seaboard of Britain and all around Ireland. It is absent from part of Liverpool Bay. It occurs in Orkney but not Shetland and extends south down the east coast of Scotland to Aberdeen. On the east coast is more or less continuous, extending from the north of Scotland, along the west coasts of Britain and along all coasts of the Irish Sea. Records detailing its worldwide distribution are limited, but it is probably that their range extends further south to Mauritania, through western and eastern parts of the Mediterranean Sea. It is rare or absent from offshore islands. It is common in the northern Adriatic and occurs at locations in the Aegean and Black Seas. Vertical distribution Chthamalus montagui is dominant over Chthamalus stellatus in more sheltered sites (Southward, 1976; Crisp et al., 1981; Burrows et al., 1992). Where their distributions overlap Chthamalus montagui has a greater vertical distribution above 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). Near its northern limit in Scotland Chthamalus montagui is limited to a narrow band at the top of the shore due to competition with Semibalanus balanoides (Kendall & Bedford, 1987), and the influence of lower temperatures. Poor settlement of Chthamalus spp. also usually occurs. The higher the species occurs up on the shore, the more resistant to desiccation influences they tend to be (Southward, 1955b). 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 distribution of Chthamalus spp. is not affected by small increases in algal cover. However, rapid increases to 100 % can lead to a massive decline in barnacle populations, declining to almost zero in a year or two (Southward, 1991). Hawkins & Hartnoll (1982) found that the lower shore level limit was controlled by the presence of algal turf. 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. are warm water species, with their northern limit of distribution in Britain. They tend to be more tolerant to temperature increases and desiccation than Semibalanus balanoides. Southward (1976) found that in Cornwall and Devon, where the barnacle is common, it dominates the upper half of the barnacle zone. 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 temporary decrease in sea temperatures (Southward, 1991). Since 1981 there has been a general increase in Chthamalus (Southward, 1991), maybe corresponding with gradual climate warming. Southward & Crisp (1954) noted that in 1948-51, during high temperatures in the British Isles Chthamalus dominated over Semibalanus balanoides, and during 1951-52, 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, 1955b).

Substratum preferences	Artificial (e.g. metal/wood/concrete) Large to very large boulders Bedrock	Physiographic preferences	Open coast Enclosed coast / Embayment
Biological zone	Upper Eulittoral Mid Eulittoral	Wave exposure	Very Exposed Exposed Moderately Exposed Sheltered
Tidal stream strength/Water flow	Very Strong (>6 kn) Strong (3-6 kn) Moderately Strong (1-3 kn) Weak (<1 kn)	Salinity	Full (30-40 psu)
Habitat Preferences Additional Information
Distribution References	Burrows et al., 1992, Rainbow, 1984, Hayward & Ryland, 1995b, Moore & Kitching, 1939, Bassindale, 1964, Kendall & Bedford, 1987, Crisp et al., 1981, Pannacciulli & Relini, 2000, Hawkins & Hartnoll, 1982, Southward, 1991, Southward, 1976, Southward & Crisp, 1954, Southward, 1955(b), Barnes, 1953, Barnes et al., 1963,