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

Crayfish often become invasive when introduced to new waters. From the late 19th to the late 20th century, the commercial import of North American species (e.g., Faxonius limosus, Pacifastacus leniusculus, Procambarus clarkii) into Europe for food, ornamental aquaculture, and restocking native crayfish populations after crayfish plague succeeded due to their adaptability, high reproductive rates, and resilience. Extensive baited-trap monitoring of Piedmont lakes carried in 2025 confirmed the occurrence of two invasive crayfish species (F. limosus, and P. clarkii) in 10 of 17 lakes and recorded P. clarkii for the first time ever in lakes Pistono, San Michele, and Sirio, 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.