In the battle against an invasive species that has devastated Italy's Adriatic fisheries, scientists have turned to an unlikely ally: the common octopus. From a fishing trawler off the coast of Cesenatico, researchers are releasing thousands of tiny octopuses into the sea, hoping they will prey on the blue crabs that have wreaked havoc on local shellfish.
"We chose the octopus because, in the wild, it is a formidable predator of crustaceans," Antonio Casalini, an aquaculture technician at the University of Bologna, told AFP.
The blue crab, native to the North American Atlantic coast, arrived in the Mediterranean decades ago, likely via ship ballast water. But in 2023, its population exploded, obliterating the mussels, clams, and oysters that the Po Delta is famous for. The surge is attributed to climate change: warmer waters have made the crabs more active and voracious.
"With warming waters, the crabs have become more active and voracious," fisherman Bellan told the Associated Press in 2023. Enrica Franchi, a marine biologist at the University of Siena, explained that the crabs previously struggled when water temperatures dropped below 10°C, but now find ideal conditions year-round.
The damage has been staggering. Authorities in Emilia-Romagna reported nearly €17 million in losses since 2022, while farming and fishing group Coldiretti estimates the total for Italy at around €200 million. The northern Veneto region has also been badly affected.
"It eats everything including young clams lying on the seabed," said Davide Sanulli, a fisherman and mussel farmer who has been assisting the research team.
Octo-Blu project
Launched last year with funding from the Emilia-Romagna region, the 'Octo-Blu' project aims to boost octopus numbers as a natural counterweight to the crabs. The team breeds octopus hatchlings in tanks at a lab in Cesenatico, then releases them near underwater reefs where artificial dens made of cement and clay have been placed to help them thrive.
Since June, some 80,000 hatchlings have been released, with the team hoping to double that number by the end of August. "The idea is to establish a small community close to shore so that it can better combat the spread of the blue crab," Casalini said.
However, the project has its limitations. The common octopus prefers rocky habitats, not the sandy, warm waters of the lagoons where blue crabs are most destructive. Researchers acknowledge this, and some experts suggest seabass might be more effective. The team is also studying eels, which feed on crustacean eggs, as a complementary measure.
Despite these challenges, the pilot could still help limit blue crab numbers and reduce their impact on the Adriatic's marine environment. Pietro Emmanuele, another University of Bologna researcher, noted the crabs' incredible reproductive potential: a single female can lay millions of eggs. "Were an octopus to catch even a single female, it would make a difference," he said.
The initiative is part of broader efforts to manage the blue crab invasion, which have included exporting the crabs to the US, where they are considered a delicacy. The Italian government has previously been urged to declare a state of emergency over the crisis.
As the octopus hatchlings grow, the researchers hope they will establish a breeding population that can keep the crabs in check. Whether this strategy will succeed remains uncertain, but for the fishermen of the Adriatic, it offers a glimmer of hope.
