{"refrec":{"BRefID":20131,"RR":"<b>Severijns, N.</b> (2001). De verspreiding van <i>Ensis directus</i> (Conrad 1843) in Europa, 23 jaar na de introductie: de opmerkelijke opmars van een immigrant, <b><i>in</i></b>: <i>De Strandvlo 21(4). De Strandvlo: Driemaandelijks Tijdschrift van De Strandwerkgroep België,</i> 21(4): pp. 123-146","BEntID":20131,"PublicFlag":1,"CheckedFlag":0,"wosflag":0,"vabbflag":0,"RefStringPartII":", <b><i>in</i></b>: <i>De Strandvlo 21(4). De Strandvlo: Driemaandelijks Tijdschrift van De Strandwerkgroep België,</i> 21(4): pp. 123-146","DocTypID":8,"DocType":"Journal article","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Severijns, N.","OrigTitleTranslFlag":1,"Authorstringtrunc":"Severijns, N.","Englishabstract":"The distribution of the American jack-knife clam <i>Ensis directus</i> (Conrad, 1843) (photo 1, figure 1,2) in Europe is discussed. The first specimens of this North- American species were found in 1979 in the German Bight, near the mouth of the river Elbe (Von Cosel et al., 1982). Most probably larvae were transported to Europe in 1978 with tanker ballast water. At present, about 23 years later, <i>E. directus</i> has spread considerably along the Western-European coasts. Towards the north (table 2, figure 3) it is found up to Oslo in Norway, has spread all around the Danish coast up to the south-western part of the Ostsea and occurs also along the west coast of Sweden. Southward (table 1, figure 3) it is found on the beaches of The Netherlands and Belgium, in the south-eastern part of England (from the Humber estuary southward along the east coast to Newhaven at the English channel coast (Eno, 1998) and along the French coast as far south as Merville-Franceville (south of Le Havre) in Normandy (Severijns, 2000a, 2000b). Most probably the species will continue to further extend its area of distribution, as in different parts of it suitable habitats are within reach. The possible influence of <i>E. directus</i> on the occurrence of the local European <i>Ensis</i> and <i>Solen</i> species was discussed. Observations indicate that <i>E. arcuatus</i> (Jeffreys, 1865) and E. minor (Chenu, 1843) do not occur any more at the Belgian coast. Indeed, no significant quantities of fresh specimens have been found on Belgian beaches since 1997. Before, both species were very common and until 1997 relatively large amounts (for <i>E. arcuatus</i> even up to several hundred specimens at a time) were regularly washed ashore (e.g. Rappé, 1985, Severijns, 1994, 1996; Vanhaelen, 1997a, 1997b, 1998). <i>Solen marginatus</i>, has never been a common species at the Belgian coast, but from time to time, especially af ter several consecutive soft winters, populations of <i>Solen marginatus</i> do occur. In the past 15 years three strandings occurred: in the period April-September 1985 (several tens of fresh specimens collected; Rappé, 1985; Kerckhof, 1987), from November 1992 to March 1993 (about 50 fresh specimens collected; Vanhaelen, 1993b), and in 1997 (more than 800 fresh specimens collected; Vanhaelen, 1997b, 1999). Since <i>E. directus</i> is present at the Belgian coast since 1985, these strandings, and especially the very large stranding in 1997, indicate that <i>Solen marginatus</i> is not affected by the presence of <i>E. directus</i>. At the French coast <i>E. arcuatus</i> was strongly reduced in numbers or may even have disappeared also at most places between the Belgian-French border and the bay of the Somme. However, near Fort-Mahon significant numbers of fresh specimens of <i>E. arcuatus</i> can still be found, while also <i>Solen marginatus</i> (Pulteney, 1799) and <i>E. ensis</i> (Linnaeus, 1758) are still present there, albeit in smaller amounts (Severijns, 1999). In Villers.sur-Mer in Normandy, where <i>E. directus</i> arrived in 1996, <i>E. arcuatus, E. ensis</i> and <i>Solen marginatus</i> are also still present and their numbers seem not to have decreased (Severijns, 2000a, 2000b). It thus seems that the disappearance of <i>E. minor</i> and <i>E. arcuatus</i> in Belgium and the strong reduction or disappearance of <i>E. arcuatus</i> in the region north of the bay of the Somme in France is not re1ated to the presence of <i>E. directus</i> there. Also in British waters there is, at far as known, no evidence that <i>E. directus</i> is competing with other species of razor clams (Eno, 1998). However, more observations and study about this would be very useful.","AbstractOtherLang":"In deze bijdrage wordt de verspreiding van de Amerikaanse zwaardschede <i>Ensis directus</i> (Conrad, 1843) in Europa toegelicht. Na een eerder trage start in de eerste drie jaar na haar introductie, in 1978, heeft <i>E. directus</i> zich in de daaropvolgende jaren zeer snel langs de Europese kusten verspreid, en dit zowel in noordelijke als in zuidelijke richting. Hoewel de snelheid sinds 1990 iets verminderd is, breidt <i>E. directus</i> momenteel, meer dan 20 jaar na haar aankomst in Europa, haar verspreidingsgebied toch nog steeds verder uit. In het noorden komt ze voor tot Oslo in Noorwegen en heeft ze zich rond gans Denemarken en de westkust van Zweden verspreid tot in het meest zuidwestelijke deel van de Oostzee. In Engeland komt ze voor vanaf het estuarium van de Humber zuidwaarts langs de oostkust, tot bij Newhaven langs de Engelse kanaalkust. In zuidelijke richting is ze reeds gemeld tot aan de monding van de Ome, op het strand van Merville-FranceviUe, ten zuiden van Le Havre. Waarschijnlijk heeft ze zich intussen ook al verder in Normandië gevestigd maarwaarnemingen daarover ontbreken voorlopig nog. Opvallend is dat <i>E. directus</i> in vrij korte tijd zeer grote populaties opbouwt. Onderzoek naar het feit of ze daarbij de locale <i>Ensis</i>- en <i>Solen</i>-soorten verdringt, duidt er op dat dit waarschijnlijk niet het geval is.","BibLvlCode":"AMS","StandardTitle":"De verspreiding van <i>Ensis directus</i> (Conrad 1843) in Europa, 23 jaar na de introductie: de opmerkelijke opmars van een immigrant","OrigTitleLangCode":"nl","OrigTitleLangCodeExtended":"dut","OrigTitleLangID":41,"DateLastModified":{"date":"2025-08-01 01:33:50.237514","timezone_type":1,"timezone":"+02:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":2001,"MonPub":null,"DateUpdate":"2025-07-25","DateCreate":"2001-11-07","SecASFANote":null,"ConfID":null,"PeerRev":0,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":1},"refs":null,"anarec":{"AnaID":20131,"PubliDate":2001,"Pagination":"123-146","XtraPublOfAnaID":null,"ISBN":null,"Volume":"21","Issue":"4","BRefMon":203052,"BRefMonRR":"(2001). 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