‘A formidable predator’: Italian scientists relying on octopuses to get blue crab populations in check
A Formidable Predator: Italy's Octopus vs Crab Plan
Poinews.com – From the deck of a fishing trawler in the Adriatic, Italian researchers are tipping thousands of juvenile octopuses back into the sea — a bold biological countermeasure against the invasive blue crab that has torn through local shellfish stocks. The common octopus, long regarded as a formidable predator of crustaceans, is now being bred in laboratory tanks and deployed as a living weapon to protect one of Europe's most productive fishing grounds.
The Blue Crab Invasion and Its Economic Toll
Native to the Atlantic coast of North America, the blue crab slipped into the Mediterranean decades ago, most likely riding in the ballast water of cargo ships. For years it remained a minor nuisance, but in 2023 its population surged to catastrophic levels, wiping out the mussels, vongole veraci clams, and pink oysters that made Italy's Po Delta famous on restaurant menus across the continent.
Warming sea temperatures are widely blamed for the explosion. Fisherman Bellan told AP in 2023 that the crabs have grown "more active and voracious" as waters heat up. Enrica Franchi, a marine biologist at the University of Siena, explained that the species historically struggled when water fell below 10 °C, yet now encounters conditions close to its thermal optimum all year round.
The financial damage is staggering. Coldiretti, Italy's major farming and fishing lobby, pegs the total cost at roughly €200 million nationwide, with the northern Veneto region hit as hard as the Po Delta. Authorities in Bologna's Emilia-Romagna region reported almost €17 million in losses there since 2022 alone. Davide Sanulli, a mussel farmer and fisherman, described the crab's appetite bluntly: "It eats everything including young clams lying on the seabed." Weighing up to a kilogram and swimming with surprising agility, the crab has virtually no natural predators in its adopted waters.
The Octo-Blu Project: Breeding a Natural Countermeasure
A team at the University of Bologna launched the "Octo-Blu" project last year, funded by the Emilia-Romagna regional government, to raise common-octopus hatchlings in white water tanks at a laboratory in the port town of Cesenatico. Once large enough, the juveniles are scooped into large plastic bags and transported out to sea — sometimes aboard Sanulli's own rugged blue fishing boat — and released near underwater reefs where the team has installed cement-and-clay artificial dens to give the octopuses shelter.
Some 80,000 hatchlings have been set free since June, and the researchers aim to double that figure by the end of August, hoping a handful will mature into fully grown adults. Antonio Casalini, an aquaculture technician on the project, framed the goal plainly: "The idea is to establish a small community close to shore so that it can better combat the spread of the blue crab."
"A formidable predator of crustaceans" is exactly what the Adriatic needs right now, Casalini told AFP, underscoring why the octopus was selected over other candidate species.
The team is candid about limitations. The common octopus prefers rocky, cooler habitats and is unlikely to colonise the warm, sandy lagoon floors where the blue crab causes the most destruction. Other marine experts have pointed to seabass as a potentially more effective crab predator, and the Bologna group is simultaneously investigating eels — avid consumers of crustacean eggs — as a complementary biological control.
Even so, the pilot could still dent the crab's numbers. Pietro Emmanuele, another University of Bologna researcher, noted that a single female blue crab lays millions of eggs, most of which hatch. "Were an octopus to catch even a single female, it would make a difference," he said, arguing that sustained predation pressure, however modest, could tip the balance in favour of native shellfish.
Frequently Asked Questions
What is the Octo-Blu project? It is a University of Bologna initiative, funded by the Emilia-Romagna region and launched last year, that breeds common-octopus hatchlings in Cesenatico and releases them near artificial reef structures to prey on invasive blue crabs in the Adriatic.
How much damage has the blue crab caused in Italy? Coldiretti estimates roughly €200 million in total losses across the country. Emilia-Romagna alone recorded almost €17 million in damages from 2022 onward, and the Veneto region has been similarly affected.
Why did scientists choose the octopus specifically? The common octopus is a natural, efficient predator of crustaceans. Researchers believe that even a small resident octopus population near shore can reduce blue crab numbers enough to protect vulnerable shellfish beds.
How many octopuses have been released so far? Approximately 80,000 hatchlings have been released since June, with the team targeting a doubling of that number by the end of August.
Is the octopus strategy guaranteed to work? Not entirely. The species favours cooler, rockier habitats and may not thrive in the warm sandy lagoons where crab damage is worst. The project therefore also explores seabass and eels as supplementary biological controls.