The English Channel: Becoming like the Seas Around Japan

The European seas are known to be the recipient of several hundreds of Non-Native Species (NNS). Two main origins have been identified: from shipping, including discharge of ballast waters and biofouling, and through voluntary introduction in aquaculture. There are more than one hundred NNS recorded in the English Channel, which remains low in comparison with the number of marine invertebrate species known in the EC (>3000). The main sites of introduction are the harbours, especially Le Havre. Among these NNS, 54 species come from the seas off Japan, and are now present in 48 established populations. In this study, we provide comments on the taxonomic groups, introduction pathways, distributions and population dynamics of listed NNS in the EC. Three specific examples of invasive species are described in detail, the oyster Magallena gigas and the two crabs Hemigrapsus sanguineus and H. takanoi. These species have changed the dynamics and functioning of the foreshore and coastal ecosystems, where they make up abundant populations. In fact, the oyster is now a key species for the French economy, while the rapid expansion of both crabs could be a problem for the development of oyster and mussel aquaculture since they are predators of young bivalves.