Mya arenaria

Phylum: Mollusca
Class: Pelecypoda
Order: Myoida
Species name: Mya arenaria (Linnaeus 1758)
Synonyms: None
Common name: Soft-shelled clam, soft clam, long-necked clam.
 
Date of introduction and origin
Mya arenaria is thought to have been introduced from the American coast during the 16th or 17th century. However, there is also evidence that the Vikings transported this species to Europe from America as early as 1245 (Petersen et al. 1992).
 
Method of introduction
It may have been deliberately introduced for food or bait, or larvae may have been transported accidentally in the bilges of ships.
 
Reasons for success
Unknown.
 
Rate of spread and methods involved
This species has spread all around the coast of Britain, apparently by natural dispersal of larvae.
 
Distribution
It is found on all British and Irish coasts, and on European North Sea coasts from northern Scandinavia and the Faeroes to Arcachon in France (Seaward 1990).
 
Factors likely to influence spread and distribution
Unknown.
 
Effects on the environment
Unknown.
 
Effects on commercial interests
Unknown.
 
Control methods used and effectiveness
None used.
 
Beneficial effects
In the USA this species is considered a delicacy and is used for "clam-bakes" at the beach. However, in Britain its use as a food is uncommon.
 
Lessons to be learnt, Comments
Fossils of M. arenaria dating from up to the end of the Pleiocene Epoch which ended 1.6 million years ago show it was previously native to Europe. It is thought to have become extinct during the Pleistocene Epoch, when Europe passed through a series of ice ages (Foster 1946). It was introduced either by the Vikings or during the 16th or 17th century and has become re-established.
 
References
Foster, R.W. 1946. The genus Mya in the western Atlantic. Johnsonia, 2: 20.
 
Hayward, P.J., & Ryland, J.S. eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.
 
Petersen, K.S., Rasmussen, K.L., Heinemeler, J., & Rud, N. 1992. Clams before Columbus? Nature, 359: 679.
 
Seaward, D.R. 1990. Distribution of the marine molluscs of north west Europe. Peterborough, Nature Conservancy Council, for Conchological Society of Great Britain and Ireland.