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.
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,
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.