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Amerikaanse zwaardschede Ensis leei

Foto: Marion Haarsma


Pharidae [familie]
Ensis [genus] (5/5)
leei [soort]

Exotenpaspoort ?

Reële kans op vestiging? Ja
Betrouwbaarheid beoordeling Grote mate van zekerheid (meerdere bronnen)
Vestigingsstatus Gevestigd
Zeldzaamheid Zeer algemeen
Invasiviteit Invasief
Invasiviteit (toelichting) The American razor clam occurs along the east coast of North America from Labrador to South Carolina. It was introduced to Northwestern Europe and first discovered at the German Wadden Sea coast in 1979 (Von Cosel et al. 1982). In the following years it dispersed northwards and southwards. Factors for its invasiveness are its high adaptability to different environments: it can live in sand- and mud on tidal banks as well as intertidal to 15 m or deeper; its tolerance to lower salinity compared to other Ensis-species; its high fertility and the large dispersal capability of the larvae, which remains in the plankton for 10-30 days (Wolff 1985).
Type introductie Niet opzettelijk
Jaar van eerste introductie 1981
Jaar van eerste melding 1983
Natuurlijke verspreiding
  • Noord-Amerika
  • Noordelijke Atlantische Oceaan
  • Verspreiding in Nederland
  • Friesland
  • Groningen
  • Noord-Holland
  • Zuid-Holland
  • Zeeland
  • Verspreiding in Nederland (toelichting) The species reached the Netherlands in 1981 (Essink 1985) the first publication is of 1983 (De Boer & De Bruyne 1983). In 1984 the species had already colonized the larger part of the Netherlands (Essink 1986). Nowadays it is one of the dominant species in the coastal area of the Netherlands. Large numbers are washed up daily on the beaches and the species is also very much present in estuaries and on intertidal mudflats in the Wadden Sea and the province of Zeeland. In the coastal areas of the provinces Noord-Holland and Zuid-Holland, the species reached the highest numbers around 2010. Since then the population appears to be stable (De Bruyne et al. 2013).
  • Mariene habitats
  • Estuaria en brakwatergebieden
  • Wijze van introductie
  • Aquacultuur
  • Ballastwater schip/boot
  • Onderling verbonden waterwegen/bassins/zeeën
  • Impact
  • Nieuwe bron in voedselweb
  • Concurrentie
  • Ecologische impact (toelichting) Although the American razor clam is one of the dominant bivalve species in many places, no direct impacts on native species or the environment have been attributable to it. There are indications the species is responsible for outcompeting several other coastal bivalves. Especially its high filtercapacity is mentioned; the species might be responsible for a decline in larvae of other bivalves (De Bruyne et al. 20143). At localities where it is particular abundant, competing for space and food will most probably play a certain role.
    Economische impact (toelichting) There are no indications of any negative impact in the Netherlands. E. directus is fished commercially, but not on a large scale.


    • Cosel, R. von, J. Dörjes & U. Mühlenhardt-Siegel 1982. Die amerikanische Schwertmuschel Ensis directus (Conrad) in der Deutschen Bucht. I. Zoogeographie und Taxonomie im Vergleich mit den einheimischen Schwertmuschel-Arten. Senckenbergiana Maritima 14: 147-173.
    • Essink, K. 1985. On the occurrence of the American jack-knife clam Ensis directus (Conrad, 1843) (Bivalvia, Cultellidae) in the Dutch Wadden Sea. Basteria 49: 73-80.
    • Essink, K. 1986. Note on the distribution of the American jack-knife clam Ensis directus (Conrad, 1843) in N.W. Europe (Bivalvia, Cultellidae). Basteria 50: 33-34.
    • Jensen, K.R. 2010. NOBANIS – Invasive Alien Species Fact Sheet – Ensis americanus. In: Identification key to marine invasive species in Nordic waters. [link]
    • Boer, Th. W. & R.H. de Bruyne 1983. De Amerikaanse zwaardschede Ensis directus (Conrad, 1843) in Nederland. Basteria 47: 154.
    • Wolff, W.J. 2005. Non-indigenous marine and estuarine species in The Netherlands. Zoölogische Mededelingen 79: 1-116. [link]