Spatiotemporal trends for exotic species in French freshwater ecosystems: where are we now?

We compiled a list of 148 exotic species in French inland freshwaters, comprising 36 plant species and 112 animals, including 50 invertebrates, 7 amphibians, 1 reptile, 25 fish, 22 birds and 7 mammals. Spatial distribution maps and cumulative analyses for most species indicate that exotic plants are distributed more along the west coast of France and, to a lesser extent, the Rhone basin, whereas exotic animals are clearly clumped in the north-east (Rhine Basin). The rate of introductions has increased exponentially over time. The most recent introductions (since 1992) have occurred in the Rhine Basin, from where they have then spread. Twenty-five species on our list are among the '100 worst invasive species of Europe' (DAISIE) and 11 among the worst in the world (IUCN), with six species included on both lists. The potential cumulative impact of exotic species tends to be heterogeneous across France, though the north-east appears to be more disturbed, especially by animal species. Additional research is needed on criteria for prioritising intervention measures that will help stakeholders make objective choices in the management of exotic species in aquatic ecosystems.