Evidence of an established population of Poecilia reticulata and Neocaridina davidi in metropolitan France

An established population of Trinidadian guppies (Poecilia reticulata) and Cherry shrimp (­Neocaridina davidi) has been observed in thermal waters in the Parc des Thermes of Juvignac, near Montpellier (Southern France). This is the first record of these two species in metropolitan France. Their identity has been morphologically and molecularly confirmed. According to locals, individuals of P. reticulata have been thriving in the study site at least since 2019, and those of N. davidi since 2021. The relatively long presence of both species, the high proportion of ovigerous females, and the presence of juveniles suggest favourable conditions for the reproduction of both species. Morphological trait heterogeneity in P. reticulata and N. davidi individuals indicates either a single release of different pools of individuals or multiple releases via aquarium dumping. The thermal water body may be temporarily connected to the nearby Mosson River, favouring the spread of both species. P. reticulata may only survive in the Mosson River during the summer months, while the more thermally adaptable N. davidi may survive throughout the year. These species are known to have multidimensional impacts on ecosystems and are vectors for pathogens that might impact native biota; therefore, close monitoring of the site is urged.