Introduction of non-indigenous benthic marine species in the Normand-Breton Gulf (France) over the two last centuries

Abstract

The introduction of non-indigenous species (NIS) is considered as one of the main threats to indigenous biodiversity, and because their eradication after introduction remains highly challenging and debatable, the prevention of their introduction and dispersion is crucial. Exploring the spatio-temporal patterns of introduction of NIS may allow identifying the vectors of introduction and dispersion, and thus may avoid future introductions. However, historical data are often lacking, especially in the marine realm, and many marine NIS are detected when already well-established in an area. Here we built a database gathering all the data of the macro-zoobenthos recorded since the beginning of the 18th century in the Normand-Breton Gulf (Western English Channel, France). We collected 97,000 data on 7,400 stations, corresponding to more than 2,100 species, among which at least 60 were NIS. These NIS were mainly introduced during the last decades and are mainly distributed within and around shellfish farms, and, to a lesser extent, around the ports. The natural isolation of the Gulf, due to strong gyres, as well the absence of large ports, and the massive development of shellfish farming explains the strong influence of this human activity in the introduction of NIS. The constant exchanges between different areas of the cultivated species and the associated material should be strongly controlled to avoid any additional introduction in the future.