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Blue Crabs Have Taken Over the Adriatic Sea. To Fight Them Off, Italian Researchers Just Released Thousands of Baby Octopuses

Although prized in the United States, the crustaceans have been decimating ecosystems and the fishing industry in Italy. Experts hope that an army of natural predators—common octopuses—can help contain the invasive species’ spread

Margherita Bassi
people carrying a bag with an octopus inside it
Researchers have spent the past two years studying the interactions between common octopuses and blue crabs and perfecting breeding techniques. Regione Emilia-Romagna

Blue crabs have invaded the Adriatic Sea, wrecking Italy’s ecosystems and fishing economy. To fight the non-native species, government officials and researchers have recruited an eight-armed ally. This summer, they’ve released into the sea tens of thousands of lab-hatched baby octopuses, which will grow up to be natural predators of the pesky crustaceans, according to a statement, per a translation by Smithsonian magazine.

Blue crabs are native to the Atlantic Coast of the Americas. They likely hitched a ride to the Mediterranean Sea—and its northernmost arm, the Adriatic—via ships’ ballast water, carried for stability purposes. The crustaceans were first spotted in the Mediterranean in the early 1900s, but their numbers and range have surged in the past decade.

Blue crabs
Blue crabs are native to the eastern coast of the Americas. wpopp via Wikimedia Commons under CC BY-SA 3.0

Now, the cerulean-colored crabs are decimating populations of local mussels, clams, crustaceans and fish. They’re also destroying fishing equipment with their strong claws. In 2024, experts estimated that the species had caused approximately $116 million in economic damage in Italy.

“The blue crab isn’t just an invasive species; it’s one of the most serious emergencies to hit our sea in recent years,” says Alessio Mammi, the Emilia-Romagna region’s councilor for agriculture, agri-food, hunting and fishing, in the statement.

To address this emergency, the local government is funding an experimental project conducted by the University of Bologna called Octo-Blu. The project started in 2024 to understand whether the common octopus could slow the spread of blue crabs.

Octo-Blu researchers picked the common octopus because of its hardy and quick-reproducing nature, and because the project can contribute to the existing population, Antonio Casalini, an aquaculture researcher at the University of Bologna, tells Scientific American’s Gennaro Tomma.

Quick fact: What are Italians doing with all those blue crabs?

Few Italians will eat the crustaceans, which are prized in the U.S. Fishers in the European country had been incinerating any pests they unintentionally hauled up, but recently, many have turned to exporting their unwanted blue crabs, reports the Associated Press’ Colleen Barry.

After roughly two years of studying the crab species, developing octopus breeding techniques and investigating the dynamic between the two animals, the Octo-Blue team released the first octopus hatchlings on June 11 and 17, according to the statement. Last month, researchers released even more of the young creatures, in their paralarval stage, along with a female octopus. So far, they’ve put at least 130,000 octopuses into the Adriatic, per Scientific American.

“The project is appropriate as a carefully controlled pilot experiment, but it is not yet a proven effective control strategy,” Rom Lipcius, a marine ecologist at the Virginia Institute of Marine Science who isn’t involved in the project, tells New Scientist’s Alessio Cozzolino.

The approach has some shortcomings. The common octopus doesn’t usually inhabit sandy, warm marine habitats of Italy’s lagoon areas most impacted by the blue crab, reports the Agence-France Presse’s Umberto Bacchi, although the researchers are taking this into account. Additionally, only 1 percent of the millimeters-long hatchlings are expected to survive into adulthood, reports New Scientist. But those that do mature could eventually each munch on up to four blue crabs per day.

The team started the field trials after witnessing young octopuses in the lab hunting blue crabs, including fairly large ones weighing around one pound, Laura Gentile, a marine biologist at the University of Bologna, tells the Independent’s Frankie Lister-Fell. “That’s an encouraging sign biologically.”

Over the next few months, the researchers will monitor the octopuses by conducting surveys during scuba dives and by working with local fishers, who will contact the team if they spot the creatures, Gentile tells Ayesha Rascoe on NPR’s “Weekend Edition Sunday.” They hope to know whether the army of cephalopods made a dent in the blue crab population by the end of the year, reports New Scientist.

Margherita Bassi

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