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Ecosystem sensitivity to invasive species (EnSIS)

Research project SD/NS/09A (Research action SD)

Persons :

  • Dr.  DEGRAER Steven - Universiteit Gent (UGent)
    Coordinator of the project
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011
  • Dhr.  STIENEN Eric - Instituut voor natuur- en bosonderzoek (IN)
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011
  • Mevr.  VAN LANCKER Vera - Royal Belgian Institute of Natural Sciences ()
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011
  • M.  KERCKHOF Francis - Royal Belgian Institute of Natural Sciences ()
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011
  • Prof. dr.  VINCX Magda - Universiteit Gent (UGent)
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011
  • Mevr.  MERCKX Béa - Universiteit Gent (UGent)
    Financed belgian partner
    Duration: 1/3/2009-30/6/2011

Description :


The introduction of invasive species is a major problem to marine ecosystems. The American jack knife clam Ensis directus represents a well-investigated and -documented example of such invasion in North-West European coastal waters. Given its high densities and habitat preferences, a major impact onto the Abra alba community, the biologically highest valuated macrobenthic community along the Belgian coast, was hypothesized. The high densities in combination with its fast growth are expected to impact on the foraging behaviour of larger predators at sea (e.g. sea birds) and further feed the discussion on a possible future commercial exploitation of the species. However, before being able to tackle both issues, still many ecological baseline questions remain unanswered.


Several ecological aspects, regarding E. directus in the Belgian part of the North Sea (BPNS), are considered highly important both from an ecological and socio-economic perspective, but reliable data on these aspects is currently lacking. This study aims at filling this gap in knowledge, focusing on three overarching objectives:
1. To describe the ecological features of E. directus in Belgian waters
2. To evaluate the ecological impacts of E. directus’ introduction into Belgian waters
3. To assess the impact of possible E. directus’ fisheries in Belgian waters

Within each of these main objectives, several more specific issues are targeted.


As no reliable data on Ensis spp. Populations are available from the BPNS, a first necessary step is to collect baseline field information on E. directus, using the most appropriate and reliable sampling techniques. This newly collected data on E. directus’ distribution as well as population size and structure, in relation to habitat features and accompanying macrobenthic fauna, will then feed the ecological features issue: its habitat and spatial distribution will be directly characterized or assessed as well as mapped through habitat suitability modeling and its accompanying macrobenthic species assemblage will be qualified and quantified. Based on this knowledge the impact of E. directus on the spatial distribution of wintering seaducks (common scoter Melanitta nigra) in the BPNS will be assessed. The potential impact of E. directus on the indigenous macrobenthic fauna will be evaluated through a comparison of existing macrobenthic data obtained prior to and after its introduction in 1987. We will finally address the impact of a possible future targeted fishery on its accompanying macrofauna (habitat suitability modeling, biological trait analysis) and on its population structure and dynamics.

Interaction between the different partners

Given the need for a wide expertise regarding E. directus and, by extension, macrobenthos and its habitat in general, a research team with a diverse expertise was set up. Each partner brings in a specific expertise, needed to comply with the objectives of this project. Having a rich background in (1) invasive species’ field biology and macrobenthos research in general, (2) the provision of (full-coverage) environmental information on the BPNS, and (3) the application of acoustic techniques in the marine environment, the RBINS-MUMM team is selected as project coordinator. This macrobenthos expertise is completed with the macrobenthos expertise from UGENT-MBS, more specifically its experiences with habitat suitability modeling and grain size analysis, and from IMARES, our foreign partner (the Netherlands) with a unique expertise in Ensis spp. Stock assessment. The ILVO-Fisheries brings its data on the spatial distribution of E. directus in the BPNS. Supplementary expertise for seaducks was retrieved from INBO.

Expected results and/or products

1. Newly collected data, partim E. directus sampling, delivered to BMDC-IDOD database.
2. Newly collected data, partim acoustic habitat characterization, delivered to BMDC-IDOD database.
3. Habitat suitability model for E. directus established.
4. Ensis directus distribution maps for the BPNS available.
5. Trophic relationship between common scoter M. nigra and E. directus assessed.
6. Effect of E. directus invasion on indigenous macrobenthos quantified.
7. Feasibility of E. directus fisheries in Belgian waters evaluated: ecological and sustainability implications




General project coordination, field data acquisition and sample processing, integration of partners activities: population structure, predation, impact on local macrobenthic communities, habitat preferences, spatial distribution, potential for exploitation.

Development of habitat suitability models and maps for E. directus, macrobenthos database “MacroDat” put at disposal of the project, distribution maps, impact of E. directus on indigenous macrobenthos.


Expertise and equipment for benthic data acquisition and processing put at disposal of the project, data acquisition in Dutch waters, database to merge Dutch and newly acquired Belgian data, evaluation of potential impacts by Ensis targeted fisheries.


Quantification of the relationship between E. directus and the common scoter Melanitta nigra.


Data on spatial distribution of E. directus put at disposal of project

Contact Information

Steven Degraer / Jean-Sébastien Houziaux / Francis Kerckhof / Vera Van Lancker
Royal Belgian Institute of Natural Sciences, Management Unit of the North Sea Mathematical Models
Gulledelle 100, B-1200 Brussels
Tel: 02 7732103, Fax: 02 7732112

Magda Vincx / Bea Merckx
Ghent University, Biology Department, Marine Biology Section
Krijgslaan 281 – S8, 9000 Gent
Tel: 09 2648529, Fax: 09 2648598

Eric Stienen / Wouter Courtens
Research Institute for Nature and Forest
Kliniekstraat 25, B-1070 Brussels
Tel: 02 5581828, Fax: 02 5581805
E-mail :

Johan Craeymeersch
Wageningen IMARES
Institute for Marine Resources and Ecosystem Studies
P.O Box 77, 4400 AB Yerseke, the Netherlands
visitor's address: Korringaweg 5, Yerseke, the Netherlands
Tel: +31 317 487075, Fax: +31 317 487359

Kris Hostens / Gert Van Hoey
ILVO - Fisheries
Ankerstraat 1, 8400 Oostende
Tel. + 32 (0) 59 56 98 38
Fax. + 32 (0) 59 33 06 29

Follow-up Committee

Nathalie De Snijder, Natuurpunt vzw
Marcel Rozemeijer, Senior Policy Advisor, Rijkswaterstat Waterdienst (NL)
Willy Versluys, Reder ter Zeevisserij
Danny Huyghebaert, Project coordinator, Stichting Duurzame Visserijontwikkeling vzw (SDVO)
Marc De Zutter, Voorzitter, Vlaamse Schelpdier – en viscoöperatie cvba (VSVC)
Marie-Celine Godin. Institut Bruxellois pour la Gestion de l'Environnement, Service Stratégie biodiversité
Elke Van den Broeke, Adjunct van de Directeur, Vlaamse Overheid, Departement Leefmilieu, Natuur en Energie - 3G29, Afdeling Milieu-, Natuur- en Energiebeleid, Dienst Beleidsvoorbereiding en -evaluatie

Documentation :

Ecosystem sensitivity to invasive species : final report  Degraer, Steven - Merckx, Béa - Stienen, Eric ... et al  Brussels : Federal Science Policy, 2012 (SP2469)
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