How an American blue crab took over Italian lagoons | CNN

The story of an American blue crab taking over Italian lagoons describes how invasive species upended the clam fishery in northeastern Italy. In the Scardovari lagoon in the Po River Delta, two fisherwomen, Oscarina Soncin and Giovanna Pizzo, had hauled in more than 4 pounds of clams each morning for over two decades, operating one of Europe’s largest clam-harvesting sites. Their work gained international attention, including a National Geographic profile in 2021. But in 2023, they began finding broken shells without clams inside, and the problem worsened until the family gave up its fishing license in 2024 after invasive blue crabs destroyed local clam beds. The Manila clam (Ruditapes philippinarum), introduced to Italy in the early 1980s, once sustained production up to 55,000 metric tons annually. Scientists attribute the crab surge to nutrient-rich waters and warming temperatures that have produced milder winters, helping crabs multiply rapidly and devastate harvests, with Scardovari’s annual clam harvests falling by 93% within three years.