An American blue crab took over Italian lagoons. Now fishers are looking for new careers
Blue Crab Invasion Transforms Italian Lagoon Fisheries
A New Challenger in Ancient Waters
An American blue crab took over the Scardovari lagoon, fundamentally changing life for local fisherwomen Oscarina Soncin and Giovanna Pizzo. As dawn broke over the northeastern Italian coastline, the two experienced women maneuvered their vessel through one of Europe’s most significant clam-harvesting zones. Icy waters reached their knees as they dragged metal rakes across the ocean floor, stirring up sediment, sand, and the area’s renowned Manila clams into collection nets. Together, these women had spent over twenty years gathering more than four pounds of clams daily from the Po River Delta waters. Their remarkable success attracted worldwide recognition, including a feature by National Geographic magazine in 2021. The pair enjoyed financial stability and the liberating sensation of working on open water.
Everything changed beginning in 2023 when they started retrieving empty shells without any meat inside. An American blue crab took their livelihood by consuming the Manila clams that sustained generations of local harvesters. Extended hours on the water became necessary to meet their daily targets, yet success remained uncertain. This crustacean, highly valued as seafood in Maryland, along America’s eastern coast and the Gulf of Mexico, had completely dominated the Po Delta ecosystem. The invasive species was devouring the Manila clam, a cultural cornerstone that features prominently in Italian cooking. Italy ranks as the world’s second-largest Manila clam producer following China, with numerous Po Delta lagoons serving as the industry’s central hub.
Climate Change Fuels Ecological Transformation
Within just three years, Atlantic crabs revolutionized the entire fishery. An American blue crab took center stage as annual clam production in the Scardovari lagoon 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 various marine organisms. However, rising global temperatures have elevated ocean warmth and produced gentler winter seasons, enabling crab populations to multiply quickly while consuming clams at unprecedented rates.
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 local fishers—representing forty percent of consortium membership—have abandoned their licenses and transitioned to different professions. Some refused to surrender their traditional trade and are attempting to adjust to this enormous environmental transformation. An American blue crab took more than just clams; it took entire careers and forced communities to adapt to a new reality.
Multiple Factors Drive Population Boom
Blue crabs circulated quietly around Po Delta lagoons for many decades without causing major disruption. Scientists remain uncertain about all contributing factors behind the recent population explosion, though researchers emphasize 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 biodiversity. As Italy’s longest river, the Po transports abundant nutrients to the lagoons from both natural origins and human activities such as agriculture, creating food surpluses for aquatic creatures including blue crabs.
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 additional insight into the situation. The crabs also dig into muddy seabeds to conceal themselves from predators and endure colder winter months more effectively. An American blue crab took advantage of these conditions, thriving where once it remained a rare visitor. In 2022, northern Italy experienced its most devastating 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 subsequent flooding the following year scattered larvae and young crabs throughout the entire delta region. Mediterranean water currents helped distribute the expanding population even further across the lagoon system.
