Elminius modestus

Phylum: Crustacea
Class: Maxillopoda
Order: Thoracica
Species name: Elminius modestus Darwin 1854
Synonyms: None
Common name: None
Date of introduction and origin
Elminius modestus was first found in Chichester Harbour, Hampshire, in 1945 where it is believed to have arrived sometime between 1940 and 1943 (Bishop 1947; Crisp 1958). This species naturally occurs in Australasia and was introduced from Australia or New Zealand (Crisp 1958).
Method of introduction
It is transported on ships' hulls or possibly on flying boats (M. Barnes pers. comm.). There is also possible transport of pelagic larvae in ballast water.
Reasons for success
Elminius modestus grows rapidly and it withstands reduced salinity, turbid waters, lower temperatures than the native barnacles Chthamalus spp. and higher temperatures than the native barnacles Balanus spp. Its initial growth rate can be 6 mm in 40 days and it reaches maturity in its first season. It produces several broods per year (Semibalanus balanoides only produces one brood per year and earlier in the season). It can grow both high up the shore and in the sublittoral.
Rate of spread and methods involved
It has a fairly rapid rate of spread (Crisp, 1958). This involves marginal transport through pelagic larval dispersal and remote dispersal through adult transport on ships' hulls Crisp (1958). See Crisp (1958) for patterns of spread around Britain between 1940 and 1960, in which time it spread from Southampton Water to the borders of Scotland. This species spread from Chichester Harbour to Shetland in 38 years. It arrived in Shetland by remote dispersal (Hiscock, Hiscock & Baker 1978) but by 1986 it could not be found there.
This barnacle is distributed all around the British mainland coast (Crisp 1958, Collins 1959). It has also recently been reported from the Outer Hebrides (Howson, Connor & Holt 1994). It is found on the Atlantic coasts of Europe from Germany to Gibraltar (Barnes & Barnes 1966).
Factors likely to influence spread and distribution
Shipping is very likely to effect remote dispersal. Low water temperature is likely to restrict northwards spread of this species. Barnes & Barnes (1960) described how Elminius increased considerably in abundance in the Clyde only following the warm summer of 1959.
Effects on the environment
In northern areas, such s the British Isles, Elminius modestus competes with Semibalanus balanoides (Crisp 1958), whereas in southern Europe it competes with Chthamalus species as well. E. modestus is, however, also found in low or variable salinity habitats where native S. balanoides does not survive. Balanus improvisus seems to be retreating where it is in competition with E. modestus (Crisp 1958; Hayward & Ryland 1990). Balanus improvisus may have been displaced from the Tamar estuary, Devon and Cornwall, and become extremely rare in the Dart, Devon, as a result of competition from E. modestus (A. Southward pers. comm.). It has been suggested that since it produces a larger number of larval stages in the summer than S. balanoides, it may be in direct competition with other components of the zooplankton, notably the larval stages of other benthic species (Crisp 1958; Farnham 1980).
Effects on commercial interests
It is a fouling organism in favourable conditions.
Control methods used and effectiveness
Ships' hulls and buoys are scraped to remove barnacles.
Beneficial effects
None known.
Barnes, H., & Barnes, M. 1960. Recent spread and present distribution of the barnacle Elminius modestus Darwin in north-west Europe. Proceedings of the Zoological Society of London, 135: 137-145.
Barnes, H., & Barnes, M. 1966. Ecological and zoogeographical observations on some of the common intertidal cirripedes of the coasts of the western European mainland in June-September, 1963. In: Some contemporary studies in Marine Science, ed. by H. Barnes, 83-105,
Bishop, M.W.H. 1947. Establishment of an immigrant barnacle in British coastal waters. Nature, 159: 501.
Collins, J. 1959. Elminius modestus in the Stour Estuary. Transactions of the Suffolk Naturalists' Society, 11: 240-241.
Crisp, D.J. 1958. The spread of Elminius modestus Darwin in north-west Europe. Journal of the Marine Biological Association of the United Kingdom, 37: 483-520.
Farnham, W.F. 1980. Studies on aliens in the marine flora of southern England. In: The shore environment, volume 2: ecosystems, ed. by J.H. Price, D.E.G. Irvine & W.F. Farnham, 875-914. London, Academic Press. (Systematics Association Special Volume, No. 17B.)
Hayward, P.J., & Ryland, J.S., eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.
Hiscock, K., Hiscock, S., & Baker, J.M. 1978. The occurrence of the barnacle Elminius modestus in Shetland. Journal of the Marine Biological Association of the United Kingdom, 58: 627-629.
Howson, C.M., Connor, D.W., & Holt, R.H.F. 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. (Contractor: University Marine Biological Station, Millport). JNCC Report No. 164. (Marine Nature Conservation Review Report MNCR/SR/27.)
Acknowledgements (contributions from questionnaire)
Dr M. Barnes, Dunstaffnage Marine Laboratory.