While clam production has plummeted in the Po Delta, scientists in the Balearic Islands are analyzing the crab's adaptability. The combination of climate change and high ecological plasticity is allowing this species to colonize a wide variety of habitats, from coastal lagoons to wetlands. This situation has led governments and fishing communities to reconsider their relationship with this predator.
The devastating impact on the Po Delta
In the Scardovari lagoon, in northeastern Italy, harvesting Manila clams was the livelihood of hundreds of families. However, since 2023, the annual clam catch has plummeted by 93% , from 4.800 tons to a mere 340. In the neighboring Goro lagoon, production has fallen by 70% compared to the previous decade, according to data from the Aquaculture Advisory Council. The culprit: the blue crab, which devours both seed clams and adult clams.
The crab population has exploded. Between 2022 and 2024, catches of this species in the delta increased tenfold, from 200 to 2.000 tons. More than 600 fishermen, 40% of the local fishing community, have abandoned the activity , according to the organization. Some, like Oscarina Soncin, have had to find work cleaning houses, while others, like Angela Franceschetti, have turned to crab fishing to try to survive.
The Italian government has allocated at least €10 million to the capture and disposal of these crustaceans, as well as to the installation of protective nets. Their consumption has also been promoted, but Italians remain hesitant. A Sri Lankan company, Taprobane Seafoods, has partnered with fishermen to create an export supply chain, particularly to the United States, where blue crab meat is a delicacy.
The trophic plasticity of the blue crab in the Balearic Islands
Meanwhile, a team from the Interdisciplinary Ecology Group at the University of the Balearic Islands (UIB) has published a study in the journal Estuarine, Coastal and Shelf Science that sheds light on the invasive success of this species. Analyzing 298 specimens captured in eight locations across Mallorca, Menorca, Ibiza, and Formentera , the researchers discovered that the blue crab has an extremely variable diet depending on the habitat.
In heterogeneous environments like s'Albufera de Mallorca, its diet is highly diverse and flexible, while in areas like Canyamel or the na Borges stream, it exhibits a more specialized diet. This trophic plasticity allows it to colonize everything from oligotrophic coastal lagoons to wetlands with significant continental runoff , an advantage over native species with more rigid requirements. The study also detected differences between sexes, although smaller than those observed between ecosystems.
The authors emphasize that understanding this variability is crucial for designing more effective management strategies. The research, part of the Iberostar–UIB Chair of the Sea and Biodibal projects , establishes a scientific basis for assessing how the blue crab interacts with coastal ecosystems and how its ecological impacts may evolve.
Control and adaptation strategies
Faced with the difficulty of eradicating the blue crab, both Italy and Spain are seeking ways to adapt. In the Po Delta, the fishermen who still persevere combine crab fishing with maintaining their clam and mussel farms. Their collaboration with Taprobane Seafoods aims to transform a threat into an economic opportunity , although the local price of crab remains low and domestic consumption is limited.
In the Balearic Islands, scientists are stressing the need to monitor the species' expansion and its impact on native communities. The warming of the Mediterranean and milder winters are lengthening the crab's reproductive period , which could worsen the situation in the coming years. Meanwhile, local authorities and research centers are maintaining constant vigilance to anticipate new outbreaks.
The story of fisherwomen like Giovanna Pizzo, who after 34 years of harvesting clams now works in a fish processing plant, reflects the human drama behind this ecological crisis. The blue crab is here to stay , and the only way out seems to be learning to coexist with it, whether by catching it, exporting it, or studying its behavior to minimize the damage.
