Slipper limpet

Crepidula fornicata


Photo credit: ©Paul Brazier - CCW
Crepidula fornicata
Common names:
  • Slipper limpet, American slipper limpet, Common Atlantic slippershell

  • Marine. Found in the area around the low water mark and into the shallow subtidal

  • This species has an oval shell, up to 5 cm in length, with a much reduced spire. The large aperture has a shelf, or septum, extending half its length. The shell is smooth with irregular growth lines and white, cream, yellow or pinkish in colour with streaks or blotches of red or brown. Slipper limpets are commonly found in curved chains of up to 12 animals. Large shells are found at the bottom of the chain, with the shells becoming progressively smaller towards the top.
  • Download N.I.E.A. ID guide

Origin and Distribution:
  • Originally found on the east coast of the Americas between Canada and Mexico. Now introduced to British-Columbia, Washington state, Japan and Europe, where it is found on the Atlantic coast between Denmark and Spain, in Sicily and the Adriatic Sea.

  • In shallow bays where the slipper limpet has been introduced in France, it can completely smother the sediment creating beds with several thousand individuals per m2. Dense aggregations of slipper limpet trap suspended silt, faeces and pseudofaeces altering the benthic habitat. Where slipper limpet stacks are abundant, few other bivalves can live amongst them. The slipper limpet is a serious threat to oyster beds because of this.
  • It has also been observed that live maerl thalli, which are a protected species and form an important protected habitat, become covered in slipper limpets and the spaces between the thalli of the bed become clogged with silt; this kills the maerl thalli and dramatically alters associated communities.
  • No management measures have proven effective for this species in this habitat.

Is it found in Ireland?
  • It is found in both Ireland and Northern Ireland.
  • The only recorded viable population in Northern Ireland was documented in 2009 in Belfast Lough. Other records exist from around Ireland over the last century including: Ballinakill Bay, Carlingford Lough, Dungarven Bay, Kenmare Bay and Clew Bay. However, none of these sites are currently thought to be supporting C. fornicata.
  • More information can be found at NBDC and NBN Atlas NI.

You can help by reporting any sightings:

Static Distribution Map as of December 2019 - Courtesy of CEDaR

How did it get here?
  • C. fornicata most likely arrived in Ireland with consignments of mussels. Other possible pathways include; with consignments of oysters, on drifting materials or due to dispersal of larvae.

Further Resources: 
Prevent Spread
  • Aquaculture managers and owners should avoid getting spat material from areas that are known to have slipper limpet present or nearby.
  • Report all sightings.
  • Ensure that water equipment (e.g. kayaks, fishing rods, Wellington boots) are clean and dry before using in another water body. See Check Clean Dry for further information. 

Species Related Files:

Invasive Species Ireland

Invasive Species Ireland