Does Manila Clam cultivation affect the Lanice conchilega (Pallas) bioherms of the Chausey archipelago ? - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2006

Does Manila Clam cultivation affect the Lanice conchilega (Pallas) bioherms of the Chausey archipelago ?

Résumé

Located within the Normand-Britain Gulf, the Chausey archipelago (total surface of 5000 ha) is submitted to an extreme megatidal regime (tidal range of 14 m), revealing at low spring tide 1900 ha of tidal flats. Since the last decade, shellfish farming of the Chausey islands has greatly increased and diversified whereas no studies were conducted to assess the impact of these activities on the benthic environment. Chausey is the major national site of Manila clam R. philippinarum (Adams & Reeves) cultivation with an annual production of 120 tons. Practices related to this cultivation are very original because they are highly mechanized: seeding, net production during the early stages and harvesting of marketable individuals are made with tractor-driven machineries. The concessions are concentrated on Lanice conchilega (Pallas) bioherms. At high density, this engineer polychaete species is known to increase the diversity and to modify the sediment dynamics. The aim of this study was thus to assess the impact of manila clam cultivation on a) the natural populations of L. conchilega and b) the structure of benthic assemblages associated to these bioherms. a) In April 2005, we determined the population structures and the spatial patterns of the L. conchilega populations at three different manila clam production stages (post-harvesting, one year and two year later) and compared them to a natural site; b) Macrofauna sampling was conducted within the natural bioherms and in two 2-years concessions (just before harvestin) and one where manila clams have been just harvested. The main results are: 1) the L. conchilega populations are significantly affected within the manila clam concessions where total abundance is reduced, mean individual weight is increased and spatial pattern are highly modified; 2) the associated benthic assemblages are significantly altered with a general decrease of total abundance, species richness and thus of diversity index; however, the resulting habitat belongs to the same benthic community of the pristing one. Our results will be discussed in a view to manage the manila clam cultivation wihtin the context of the sustainable development of the littoral environment.
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Dates et versions

hal-00101809 , version 1 (28-09-2006)

Identifiants

  • HAL Id : hal-00101809 , version 1

Citer

Nicolas Toupoint, Laurent Godet, Frédéric Olivier, Jérôme Fournier, Christian Retière. Does Manila Clam cultivation affect the Lanice conchilega (Pallas) bioherms of the Chausey archipelago ?. 35th Benthic Ecology Meeting, 2006, Québec City, Canada. pp.54-55. ⟨hal-00101809⟩
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