How was France invaded? 170 years of colonisation of metropolitan France by freshwater mussels

The introduction of freshwater mussels in France was unintentional and relatively recent. Two species were introduced in the second half of the nineteenth century, and a further eight after World War II. This note summarises the available information on introduced freshwater bivalves in France, focusing on the main pathways and vectors of dispersal, based on the data provided by the French National Database (INPN) and environmental DNA data. The introductions were either by sea (mainly for brackish water species, but also for Asiatic Clams), or by the European river system and its canals connecting the Danube to the Rhine (Dreissenidae, Sphaeriidae). A third mean of introduction was the transport of fish, for the Chinese pound mussel, which first established in southern France. Canals connect the major French basins (Rhine, Rhone, Seine, Loire and Garonne) and the route of dispersal of introduced species through natural hydrosystems and canals can be traced by looking at their progression, decade by decade. Fish transport within France is probably an important dispersal vector for the Chinese pound mussel, as occasional introductions appear to have contributed to its spread in the north-east and west of France. The use of the eDNA was an effective tool in completing the species distribution maps.

Automated summary

The introduction of freshwater mussels in France was unintentional and relatively recent. The available information on introduced freshwater bivalves in France, based on the data provided by the French National Database (INPN) and environmental DNA data, shows that the introductions were mainly by sea or through the European river system and canals. Fish transport within France is also an important dispersal vector. The use of eDNA was effective in completing the species distribution maps.