Scardovari, Italy — As the sun was rising, two fisherwomen dragged their boat through the Scardovari lagoon in northeastern Italy. Oscarina Soncin stood in one of the largest clam-harvesting sites in Europe — the frigid water lapping against her knees as she scraped the seafloor with a metal rake. The motion kicked mud, sand and the region’s famous delectable Manila clams into her net. Her fishing partner Giovanna Pizzo sorted the clams from the debris. For more than two decades, the duo hauled in more than 4 pounds of clams each morning from the lagoon in the Po River Delta — upending the notion that women were unsuited for such a rigorous job. Their enterprise drew international attention, inspiring a profile by National Geographic in 2021. The two enjoyed a reliable income and the feeling of freedom on the water. Then, in 2023, they started picking up broken shells with no clams inside. They had to stay on the water longer to collect their quota but weren’t always successful. A competitor had emerged and was lurking nearby: the Atlantic blue crab. The crustacean — a prized seafood in Maryland, elsewhere along the US eastern seaboard and the Gulf of Mexico — had overrun the Po Delta, devouring the cultural staple that once provided a livelihood for generations of clammers. Manila clams are woven into Italian cuisine, tossed in pasta or served steamed. Italy is the second-largest producer of the Manila clams after China — with many Po Delta lagoons at the heart of the country’s industry. Yet within three years, the Atlantic crabs have transformed the fishery. Annual clam harvests in the Scardovari lagoon, where Soncin and Pizzo worked, fell by 93 per cent. Some clam beds have no survivors. Scientists say the delta’s naturally nutrient-rich waters provide a great buffet for the crabs and other marine life. But a warming planet has increased ocean temperatures and created milder winters — allowing the crabs to multiply rapidly and feast on the clams. “My experience has taught me that anything can happen in nature,” Soncin said. “The sea can give a lot, but it can also take everything away, and that is exactly what happened to me.” Like Soncin and Pizzo, more than 600 fishers — 40 per cent of the members in the local consortium — have quit, according to the group. Many turned in their licenses and pivoted to new careers. Others refused to let go of the trade and are attempting to adapt to the massive ecological shift. The predator that found paradise Blue crabs swarmed quietly for decades around the Po Delta lagoons. No one knows all the factors behind the population’s recent boom, although researchers point to recent extreme weather events and climate change, perhaps compounded with a rise in shipping traffic over recent decades. The Po Delta is a haven for marine life, said Massimiliano Costa, director of the Po Delta Park that helps conserve and manage the local environment. As Italy’s longest river, the Po delivers plenty of nutrients to the lagoons — both from natural sources and from human activities like farming — that provide a surplus of food for sea critters, including blue crabs. Incoming tides from the Adriatic Sea continually replenish oxygen and bring in saltwater that the females need to reproduce. The crabs also burrow in the muddy seafloor to hide from predators and better withstand winter temperatures. “The introduction of eggs and larvae through maritime transport has likely occurred continuously over several decades,” Viviana Carli, a technician with the Po Delta Park field team, said. “What seems to have changed were the environmental conditions, which became much more favorable for the species, allowing the population to increase dramatically.” In 2022, northern Italy’s most severe drought in two centuries allowed salty seawater to push upstream into the Po River, creating a favorable environment for female blue crabs to reproduce and for their eggs to develop, Costa said. The following year, heavy rains and flooding dispersed larvae and juveniles throughout the delta. The broader climate conditions also shifted in the crabs’ favor. In recent decades, the Mediterranean waters have warmed to temperatures that allow the blue crabs to reproduce more successfully — sometimes multiple times within a single breeding season. Studies show warmer winters have also extended their reproduction period and reduced cold fatalities. “I never imagined … the blue crab could establish itself in the Po Delta, given our climate,” said Pizzo, who started harvesting clams because it offered good earnings from the very beginning. “This makes me think that the seasons are no longer what they used to be.” Given one female blue crab can produce millions of eggs, a population explosion in the lagoons may have been inevitable in the new environment. No matter how they were introduced to the region, the blue crabs found a paradise in the delta’s lagoons. A fruitless battle From 2022 to 2024, the number of blue crab catches has increased by 900 per cent in the Po Delta — from around 200 tons to 2,000 tons — according to the Aquaculture Advisory Council. “They completely destroy clam farms. They completely eat all the seeds, even larger Manila clams,” said Mattias Gaglio, an ecologist at the University of Ferrara. “They completely disrupt the ecological network.” The two most affected sites are the Scardovari and Goro lagoons, which often comprise most of the country’s clam production in a year, Gaglio said. In the Goro region, he and his colleagues showed clam production fell to an average of 4,000 tons in 2024 — a 70 per cent decline compared to the previous decade. The Scardovari lagoon reported annual harvests down from 4,800 tons to 340 tons since 2023. But scientists say it will be difficult, if not impossible, to rid the Italian lagoons of the blue crabs. The Italian government has invested at least 10 million Euros to catch and dispose of the crabs. The funds also support the construction of stronger fences and nets to protect the Manila clams. Officials even encouraged eating the crabs. In the US, the crustacean’s sweet meat is a delicacy. But Italians, multiple researchers said, seem to be reluctant to eat them because they associate it with damage to the local economy. It also takes much more effort to clean and cook the crabs compared to clams, which can steamed or boiled easily. In Italy, blue crab is used mostly in pet food and occasionally served in restaurants. “Any effort done to control the population has been more or less useless,” said Giuseppe Castaldelli, professor of ecology at the University of Ferrara. “Still, we don’t know what to do with the with the crab.” Because the crabs are plentiful, the local market price is low and makes it hard to turn a profit. But recently, a Sri Lankan company named Taprobane Seafoods has partnered with the fishers through the local consortium to create a new supply chain for global exports. Italian fishers catch the crabs, while the company provides expertise in processing and commercializing the food to international markets, including the US. Some locals are also employed at the processing facility. “Within months, the (blue crab) species had escalated from a minor presence to a major threat,” said Paolo Mancin, the president of the Consorzio Cooperative Pescatori del Polesine, which helps manage stocks and maintenance of the lagoons. “The partnership aims to transform an invasive species that severely impacted clam farming into a new economic opportunity for local fishermen and workers.” But none of those tactics have fully contained the invasive pinchers. Finding a future in unfamiliar waters Before the blue crab surge, Angela Franceschetti’s workday felt approachable and routine. Franceschetti is part of the Scardovari consortium, which is down to 860 members compared to 1,470 before the boom of the blue crabs. The consortium provided a quota to guide how many clams she needed to catch — along with the departure and delivery times for her boat. She could finish her daily tasks within thirty minutes to three hours. But when clam fishing stopped turning a profit for her in October 2023, she and her partner, Marco Finotti, expanded their catch to include blue crabs. Now, when she sets her wake-up alarm for the next day, the 28-year-old Franceschetti must look up the times for high and low tides. This homework helps gauge the best time to visit her 80 crab traps. Unlike clamming, a crab harvest depends entirely on the traps, which take about three to four hours to check. She sells her catch to the consortium, which delivers the crabs to Taprobane Seafoods. After lunch, she and Marco return to the lagoon to work on their clam farm for another four or five hours. Along with other members of their cooperative, they remove excess algae with rakes so it can be pushed out to sea and not suffocate the clams. They clean nets and reinforce poles before storms come in. At sunset, they catch additional bait for the crab traps or tend to their offshore mussel farms. “Through my work as a fisher, I have come to understand that climate change is not only something that affects the environment; it also directly affects my livelihood,” Franceschetti said. “Changes in temperature, weather patterns and marine conditions influence the way the ecosystem functions, and those changes inevitably impact the work of those who depend on it every day.” For Soncin, adapting to the crabs meant leaving the water altogether. After retiring from clam fishing in 2024, she began cleaning houses. The pay is similar, but the work doesn’t carry the same meaning as the decades she spent in nature. Pizzo also abandoned clam fishing after a run of 34 years and now works in a fish processing factory that is nothing like being on the water. “What I miss most is … working closely with nature and enjoying the freedom that came with our work on the water,” Soncin said.
