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Mediterranean invasive species factsheet

Similar species Mediterranean it was first reported in southern
The native species Crepidula moulinsii and France (Thau Lagoon) in 1982. Since then it has
Crepidula unguiformis could be confused with C. followed the same path as the Pacific oyster
fornicata. C. moulinsii has a more rounded and (Crassostrea gigas), having been reported also in
convex shell shape that shows a wrinkled surface Malta, Italy and Greece.
and light brown stripes whereas C. unguiformis
has a white shell of elongated shape and flatter Ecological impacts
surface. Its high-density colonies (up to several thousand
individuals per square metre) have major effects on
the macro-benthic fauna and flora, as they compete
for food with other filter-feeding invertebrates and
increase carbon release. Moreover, the production of
large amounts of faeces and pseudo-faeces,
increasing the deposition of mud, can have a
considerable impact on sediment composition and the
associated biota (such as free-living coralline algae).
An unexpected positive impact is that its feeding
activities may prevent blooms of harmful algae.

Economic impacts

The slipper limpet can become a pest on
Crepidula moulinsi. Photo: A. Pierluigi
commercial oyster and mussel farms, reducing the
productivity of aquaculture and natural harvesting
grounds. Additional costs are associated with
sorting and cleaning shells fouled by C. fornicata
before marketing. It is also known to foul man-
made structures and equipment.

Management options
Suggested prevention actions to avoid slipper
limpet settlement should include education and
public awareness-raising combined with
monitoring, particularly close to and inside
aquaculture farms. Early detection is possible by
monitoring shellfish grounds and mollusc culture
sites in the proximity of MPAs on a periodic basis.
Oyster spat, juvenile mussels or clams with
Crepidula unguiformis. Photo: Guido and P. Poppe
attached slipper limpets should be removed.
Control action in the case of this species is
feasible as its presence is sporadic in the
Brief history of its introduction and Mediterranean.
pathways
Originally from the western Atlantic, from the St Further reading
Lawrence estuary to northern Mexico, the species http://www.ciesm.org/atlas/CrepidulForni.html
was first observed in Europe on the west coast of http://www.europe-aliens.org/pdf/Crepidula_fornicata.pdf
Britain in 1872, probably introduced in association http://www.nobanis.org/speciesInfo.asp?taxaID=229
with culture oyster spat, and it then spread along
Global Invasive Species Database:
other European coasts. The slipper limpet may Drawings: Juan Varela
also potentially spread via boat fouling (in the http://www.issg.org/database/species/ecology.asp?si=60
communities encrusting a ship’s hull) or attached 0&fr=1&sts=
to floating objects and marine litter. In the

70 Monitoring Marine Invasive Species in Mediterranean MPAs: A strategy and practical guide for managers