First records of the dwarf surf clam Mulinia lateralis (Say, 1822) in Europe

This paper reports the first records of the dwarf surf clam Mulinia lateralis (Say, 1822) outside its native area, which is the western Atlantic Ocean, ranging from the Gulf of St Lawrence to the Gulf of Mexico. In 2017 and 2018 specimens were found in the Dutch coastal waters (North Sea), in the Wadden Sea and in the Westerschelde estuary, in densities of up to almost 6000 individuals per square meter. In view of its ecology and distributional range in the native area M. lateralis has the potential to become an invasive species. Its ability to quickly colonize defaunated areas, its high fecundity and short generation time, its tolerance for anoxia and temperature extremes and its efficient exploitation of the high concentrations of phytoplankton and natural seston at the sediment-water interface may bring it into competition with native species for food and space.