Crepidula fornicata is a limpet-like marine snail known as the Common Atlantic Slippersnail. It grows in curved stacks of four or five individuals, but sometimes as many as 12 snails can be stacked on top of one another. In parts of its introduced range, it can affect the survival, growth, and harvesting of commercially important shellfish.
Crepidula fornicata is a sedentary, limpet-like mollusk native to the Northwest Atlantic from Newfoundland to the Gulf of Mexico. It is often extremely abundant in lower intertidal and shallow subtidal waters. Within Europe, spread has occurred through various means, including Pacific Oyster C. Crepidula fornicata was first reported from the West Coast in Puget Sound, Washington WA in Sherwood , Galtsoff , cited by Carlton , although it may have been introduced earlier.
Some early collections, such as those in Tomales and Humboldt Bays in California Bonnet ; Bonnet , cited by Carlton , and possibly some museum specimens collected in San Francisco Bay in California Academy of Sciences , probably represent dead shells introduced with plantings of Eastern Oysters Crassostrea virginica. Crepidula fornicata is reportedly abundant in southern areas of Puget Sound Boersma et al.
In European waters, Crepidula fornicata was first reported in Liverpool Bay, England in , but did not persist there. In the late 19th century, it appeared in many English estuaries where Eastern Oysters were planted, including the Thames and many small estuaries in Essex, Suffolk and Lincolnshire , Blanchard ; Eno et al. The oysters did not become established, but C. The spread eastward was rapid, probably due to multiple vectors, including oyster transplants, hull fouling, ballast water, and larval dispersal.
The slipper limpet was found in Belgium in , the Netherlands in , and the island of Sylt, Germany and the west coast of Denmark by Blanchard ; Wolff ; Gollasch and Nehring ; Kerckhof et al. By , C. Slipper limpets are now very abundant in aquaculture and fishing grounds for Pacific Oysters Crassostrea gigas and King Scallops Pecten maximus. They occur further south in Arcachon Bay, France where it first appeared in , but never attained the high abundances seen elsewhere de Montaudouin et al.
