Proceedings/Recueil Des Communications Année : 2025

Multidisciplinary Study of the Population Dynamics of the Non-indigenous Manila Clam Ruditapes philippinarum Along the Western Coast of Cotentin, France

Résumé

Since its introduction to France in the 1970s, and to the Chausey Islands (western English Channel) at the end of the 1980s, the Manila clam Ruditapes philippinarum has increased greatly in population along the western coast of Cotentin. Distribution mapping in 2015 highlighted the presence of four main oyster reefs covering 10% of the intertidal zone. Annual censuses estimate that 6000 recreational fishers per day utilize this resource the during spring tide, harvesting approximately 120 t annually in addition to 8 t harvested commercially. We tested several hypotheses as to the larval source of the Cotentin population with a hydrodynamic MARS 3D model simulating the hydrodynamics of the region. The particulate transport model, Ichthyop, was used to simulate the dispersion of clam larvae after a month of planktonic life, with varying wind conditions and varying points of larval injection during the June-July period. This model showed that some of the larvae is transported offshore, while the majority is recruited to the western coast of Cotentin, with larvae from Chausey Islands clam farms supplying clam populations throughout the Normano-Breton Gulf. This explains the maintenance of clam stocks in spite of heavy annual harvest and supports a sustainable fishery despite the low abundance of breeding individuals.

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Dates et versions

hal-05319434 , version 1 (17-10-2025)

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O. Basuyaux, Anne-Claire Bennis, Souha Ajmi, G. Croguennec, Martial Boutet, et al.. Multidisciplinary Study of the Population Dynamics of the Non-indigenous Manila Clam Ruditapes philippinarum Along the Western Coast of Cotentin, France. COAST 2023, Oct 2023, Caen, France. Springer Nature Switzerland, pp.59-74, 2025, ⟨10.1007/978-3-031-90050-1_5⟩. ⟨hal-05319434⟩
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