Date of introduction and origin
The first known occurrence of Crepidula fornicata in
Europe was in 1872 in Liverpool Bay, but populations in this area
have since died out. Crepidula fornicata is known to have
been introduced to Essex between 1887 and 1890 from North America
(Loosanoff 1955; Crouch 1894, 1895; Orton 1912; Fretter &
Method of introduction
The individuals in Essex from which the spread of
Crepidula started were introduced in association with
imported American oysters Crassostrea virginica. This
species may also be transported on ships' hulls (Franklin &
Pickett 1974), and in ballast water in the pelagic larval phase.
Historic populations (now extinct) have also been introduced in
association with the American hard shelled clam Mercenaria
mercenaria (McMillan 1938; Minchin McGrath & Duggan
Reasons for success
Its success is probably due to a lack of predators and the
unusual method of reproduction (which relies upon individuals
settling upon each other and reproduction thus being assited
through their close proximity); and a pelagic larval stage aids the
spread once introduced.
Rate of spread and methods involved
It showed fairly rapid spread (Franklin & Pickett 1974),
from Essex to Weymouth, Dorset by 1945 (Seaward 1987), and by the
early 1950s its range had extended to Northumberland (see Minchin,
McGrath & Duggan 1995).
This species is found in southwest, south and southeast
Britain and as far north as Pembrokeshire on the west coast and
Yorkshire on the east coast (Hancock 1969; Utting & Spencer
1992; Spencer 1990; Smith 1995; Chipperfield 1951). It does not
occur in any abundance deeper than 30 metres (Barnes, Coughlan
& Holmes 1973). It also occurs off mainland Europe, as far
north as southern Norway on the Skagerak coast.
Factors likely to influence spread and distribution
Minimum winter temperatures may be important in limiting the
ability to develop extensive populations in the north of Britain
(Minchin, McGrath & Duggan 1995).
Effects on the environment
It competes with other filter-feeding invertebrates for food
and space, and in waters of high concentrations of suspended
material it encourages deposition of mud owing to the accumulation
of faeces and pseudofaeces (Barnes, Coughlan & Holmes
Effects on commercial interests
It is considered a pest on commercial oyster beds, competing
for space and food, while depositing mud on them (Utting &
Spencer 1992) and the mud rendering the substratum unsuitable for
the settlement of spat (Barnes, Coughlan & Holmes 1973). In
parts of Essex slipper limpets were said to far exceed oysters in
abundance (Walne 1956).
Control methods used and effectiveness
Dipping infested culch and oysters in saturated solutions of
brine for a short period (Hancock 1969; Franklin 1974) is the
cheapest, safest and most effective method of control. For
clearance of large beds, dredging and disposal above high water
mark has been applied (Hancock 1969).
It has been suggested that the shells may be used as oyster
culch for spatfalls in the Solent (Barnes, Coughlan & Holmes
It is thought to have been introduced to France with oysters
from England. It has attained dense concentrations of up to 1750
m-2 and in some areas has been the dominant member of the
macrofauna (Seaward 1987).
Barnes, R.S.K., Coughlan, J., & Holmes, N.J. 1973. A
preliminary survey of the macroscopic bottom fauna of the Solent,
with particular reference to Crepidula fornicata and
Ostrea edulis. Proceedings of the Malacological
Society, 40: 253-275.
Chipperfield, P.N.J. 1951. The breeding of Crepidula
fornicata in the River Blackwater, Essex. Journal of the
Marine Biological Association of the United Kingdom,
Crouch, W. 1894. On the occurrence of Crepidula
fornicata (L.) off the coast of Essex. Essex
Naturalist, 8: 36-38.
Crouch, W. 1895. On the occurrence of Crepidula
fornicata in Essex. Proceedings of the Malacological
Society, 1: 19.
Franklin, A. 1974. The destruction of the oyster pest
Crepidula fornicata by brine-dipping. Fisheries
Laboratory, Ministry of Agriculture Fisheries and Food, Lowestoft.
(Technical Report No 8).
Franklin, A., & Pickett, G.D. 1974. Recent research on
introduced oyster pests in England and Wales. Unpublished,
International Council for the Exploration of the Sea. (Paper, No.
Fretter, V., & Graham, A. 1981. The prosobranch molluscs
of Britain and Denmark, part 6. Journal of Molluscan Studies,
supplement 9, 285-363.
Hancock, D.A. 1969. Oyster pests and their control.
Burnham on Crouch, Ministry of Agriculture Fisheries and Food.
(Laboratory Leaflet (New Series), No. 19.)
Hayward, P.J., & Ryland, J.S. eds. 1990. The
marine fauna of the British Isles and north-west Europe. 2
vols. Oxford, Clarendon Press.
Loosanoff, V.L. 1955. The European oyster in American waters.
Science,121 (3135): 110-121.
McMillan, N.F. 1938. Early records of Crepidula in
English waters. Proceedings of the Malacological Society,
Minchin, D., McGrath, D., & Duggan, C.B. 1995. The slipper
limpet, Crepidula fornicata (L.), in Irish waters, with a
review of its occurrence in the north-eastern Atlantic. Journal
of Conchology, 35: 247-254.
Orton, J.H. 1912. An account of the natural history of the
slipper-limpet (Crepidula fornicata), with some
remarks on its occurrence on the oyster grounds of the Essex coast.
Journal of the Marine Biological Association of the United
Kingdom, 9: 437-443.
Seaward, D.R. 1987. The marine molluscs of Portland Harbour,
Dorset. Proceedings of the Dorset Natural History and
Archaeological Society, 108: 159-167.
Smith, S. 1995. Crepidula fornicata (L., 1758)
(Mollusca: Gastropoda) at Tenby, south west Wales. Porcupine
Newsletter, 6: 82.
Spencer, B.E. 1990. Cultivation of Pacific oysters.
Lowestoft, Ministry of Agriculture, Fisheries and Food. (Laboratory
Leaflet No. 63).
Utting, S.D., & Spencer, B.E. 1992. Introductions of
marine bivalve molluscs into the United Kingdom for commercial
culture - case histories. ICES Marine Science Symposium,
Walne, P.R. 1956. The biology and distribution of
Crepidula fornicata in Essex rivers. Ministry of
Agriculture, Fisheries and Food, Fisheries Investigations II,
Series XX, No. 6: 1-50.