Revisiting the Invasion: A Success Story of Crayfish Species in Piedmont Plain Lakes (NW Italy)

Crayfish often become invasive when introduced to new waters. The mid-20th-century commercial import of North American species (e.g., Faxonius limosus, Pacifastacus leniusculus, Procambarus clarkii) into Europe for food, pets, and restocking after crayfish plague, succeeded due to their adaptability, high reproductive rates, and resilience. Extensive baited-trap monitoring of Piedmont lakes allowed us to confirm the occurrence of the Old Non-Indigenous Crayfish Species (F. limosus, P. leniusculus, and P. clarkii), and to record P. clarkii first-ever in three additional lakes (Pistono, San Michele, and Sirio), thereby expanding our knowledge of their distribution in Piedmont freshwaters. Since all detected species are listed as Invasive Alien Species of Union Concern, protecting the ecological integrity of Piedmont’s freshwaters requires coordinated action by member states, regional authorities, policymakers, and water managers to prevent and control their spread, and to improve information sharing. Non-native crayfish occurrence is influenced not only by hydrological and habitat connectivity, and predator–prey interactions, but also by illegal activities that supply the food market.