An American blue crab took over Italian lagoons. Now fishers are looking for new careers
An American Blue Crab Took Over Italian Lagoons, Upending Local Fisheries
A Historic Catch Faces New Challenges
An American blue crab took over the waters of northeastern Italy, fundamentally changing how local fishers earn their living. Dawn broke over the Scardovari lagoon as Oscarina Soncin and Giovanna Pizzo maneuvered their vessel through shimmering waters. These two women positioned themselves within one of Europe’s most significant clam-harvesting zones, where icy currents brushed against their legs while they worked metal rakes across the ocean floor. This rhythmic movement stirred up sediment, sand, and the area’s renowned Manila clams into their waiting collection net. Together, they had spent over twenty years gathering more than four pounds of clams daily from the Po River Delta waters.
Their remarkable enterprise captured worldwide attention, earning a feature story from National Geographic magazine in 2021. The pair appreciated both their steady earnings and the independence that life on the water provided. However, everything changed beginning in 2023 when they noticed an increasing number of empty shells among their catch. Extended hours on the water failed to guarantee meeting their daily targets. An unexpected rival had appeared, silently dominating the lagoon: the Atlantic blue crab.
The Unwelcome Visitor Spreads Rapidly
An American blue crab took residence in the Po Delta ecosystem, consuming the cultural food staple that sustained generations of clam harvesters. Manila clams remain integral to Italian cooking, appearing in pasta dishes and served simply steamed. Italy ranks as the world’s second-largest producer of these clams following China, with numerous Po Delta lagoons serving as the industry’s central hub. This crustacean, highly valued as seafood in Maryland, along America’s eastern coast, and throughout the Gulf of Mexico, had completely overwhelmed the local waters.
Within just three years, the Atlantic crabs revolutionized the local fishery. Annual clam production in the Scardovari lagoon, where Soncin and Pizzo operated, plummeted by ninety-three percent. Certain clam beds now contain virtually no living specimens. Researchers explain that the delta’s naturally nutrient-dense waters create an ideal feeding ground for crabs and other aquatic creatures. However, rising global temperatures have elevated ocean warmth and produced gentler winters, enabling the crabs to multiply quickly and consume clams voraciously.
My experience has taught me that anything can happen in nature. The sea can give a lot, but it can also take everything away, and that is exactly what happened to me.
Similar to Soncin and Pizzo, over six hundred fishermen—representing forty percent of the local consortium’s membership—have abandoned their licenses and transitioned to different professions. Several others declined to surrender their trade and are trying to adjust to this enormous ecological transformation.
Climate Change Accelerates the Invasion
An American blue crab took decades to establish itself within the Po Delta lagoons before causing major disruption. Scientists remain uncertain about all elements contributing to the recent population surge, though experts highlight extreme weather patterns and climate change, possibly intensified by increased maritime traffic over recent decades. Massimiliano Costa, who directs the Po Delta Park responsible for environmental conservation, described the region as a sanctuary for marine organisms.
As Italy’s longest river, the Po transports abundant nutrients to the lagoons from both natural origins and human activities such as agriculture, creating a food surplus for sea creatures including blue crabs. Adriatic Sea tides continuously supply oxygen and deliver saltwater essential for female reproduction. The crabs also dig into muddy bottoms to conceal themselves from predators and endure colder winter months.
The introduction of eggs and larvae through maritime transport has likely occurred continuously over several decades. What seems to have changed were the environmental conditions, which became much more favorable for the species, allowing the population to increase dramatically.
Viviana Carli, a technician on the Po Delta Park field team, provided this insight. In 2022, northern Italy experienced its worst drought in two hundred years, enabling salty seawater to travel upstream into the Po River. This created optimal conditions for female blue crabs to reproduce and for their eggs to mature, according to Costa. Heavy rainfall and flooding the following year scattered larvae and young crabs across the entire delta region.
Wider climate patterns also shifted advantageously for the crabs. Mediterranean waters have warmed considerably over recent decades, creating additional habitat expansion opportunities. An American blue crab took full advantage of these changing conditions, transforming what was once a thriving clam fishery into a challenging new reality for Italian water workers seeking sustainable livelihoods.