Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 397590
Title The role of the invasive bivalve Ensis directus as food source for fish and birds in the Dutch coastal zone.
Author(s) Tulp, I.Y.M.; Craeymeersch, J.A.M.; Leopold, M.F.; Damme, C.J.G. van; Fey-Hofstede, F.E.; Verdaat, J.P.
Source Estuarine Coastal and Shelf Science 90 (2010)3. - ISSN 0272-7714 - p. 116 - 128.
Department(s) Vis
Publication type Refereed Article in a scientific journal
Publication year 2010
Keyword(s) scoter melanitta-nigra - plaice pleuronectes-platessa - eiders somateria-mollissima - southern north-sea - limanda-limanda l - feeding ecology - wadden sea - population-structure - vipera cuvier - lesser weever
Abstract The razor clam Ensis directus was introduced to Europe presumably as larvae in ballast water around 1978. Starting in the German Bight it spread northward and southward along the continental coastline. Currently it is the most common shellfish species in the Dutch coastal zone, where it mainly occurs in the Voordelta and off the Wadden Sea islands. The mean density of E. directus in the Dutch coastal zone increased from around 2–5 individuals m-2 in the late ‘90’s to around 12–19 individuals m-2 from 2002 onwards. Diet studies show that E. directus makes up a significant proportion in the current diet of plaice, sole, dab, flounder and dragonet and in the diet of eider and common scoter. In recent years E. directus contributed 20–100% of the total wet weight in fish stomachs. The proportion E. directus in the diet increases with fish length. Based on stomach contents of oiled and beached birds and of faeces samples the recent frequency of occurrence is 85–90% in eider and 26% in common scoter. Also waders, gulls and corvids prey on E. directus but the contribution to the diet is still unquantified. Because of its great burying depth the species is not easily accessible. Fish either profit from massive die-offs that regularly occur, or they extract (probably only the smaller) individuals from the sediment. Sea ducks can extract E. directus from the sediment, while shorebirds and gulls feed on dying E. directus washing up on the shore. E. directus is possibly an important food item for fish and seabirds when they occur in high densities and in the right size classes. Since the availability depends greatly on massive die-offs, shell size, burying depth and water depth, it is probably not a very reliable food source. Judging from the role E. directus currently plays for the higher trophic levels, its introduction must have caused a major change in the food relations in its distribution area.
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