International audience Since its first sighting in 2008 on the central part of the western coast of northern Cotentin, the marbled crab Pachygrapsus marmoratus has been regularly sampled in the sites where it was first reported. The presence of ovigerous females and juveniles confirmed the presence of a reproductive population in the English Channel. However, the absence of this species in other sites around the Cotentin, prospected for the survey of the progression of two invasive Hemigrapsus decapods is questionable. It is suggested that the species may have good abilities to colonize new areas, considering the larval dispersal with a long planktonic larval phase, but failed in this particular case, probably due to on-favourable conditions.