First records of alien crayfish of the Procambarus acutus species complex in Belgium

We present the first Belgian records of potentially invasive alien crayfish of the Procambarus acutus species complex, including the first confirmed record of P. acutus acutus. The species complex was observed at four different sites in three provinces in the north of the country. Only at one site the presence of a form I male specimen made identification to species level possible, based on gonopod morphology. The other three observations are considered as belonging to the P. acutus species complex. Procambarus acutus acutus is the fifth alien crayfish species known to Belgium. In Europe, it was previously only known as an established alien species from the Netherlands and Great Britain.