The Japan Times - Italian scientists bet on octopus to fight crab invasion

A team from University of Bologna is betting that the common octopus can help contain the burgeoning population of blue crab -- a voracious crustacean that has ravaged shellfish production in the Adriatic.

"We chose the octopus because, in the wild, it is a formidable predator of crustaceans," Antonio Casalini, one of the researchers, told AFP.

Native to the North American Atlantic coast, blue crabs arrived in the Mediterranean decades ago, likely transported via ballast water from ships.

But their numbers have ballooned in recent years, with the government and fishing groups linking the boom to warming waters and climate change.

With sharp, blue-tinted claws that are particularly apt at prying open shells, they have wreaked havoc in Italy's northeast -- one of Europe's top clam producing regions.

Authorities in Bologna's Emilia-Romagna region said last year the species has caused almost 17 million euros ($20 million)in damages there since 2022.

Farming and fishing group Coldiretti has put the figure at about 200 million for the whole of Italy, with the northern Veneto region also badly affected.

"It eats everything including young clams lying on the seabed," said Davide Sanulli a fishermen and mussels farmer with thick eyebrows and grizzled hair, said of the crab.

In lagoon-like areas off the Po River delta "it has caused a massacre", added the 64-year-old, who is helping the university project.

Excellent swimmers and weighing up to one kilogramme (2.2 pounds), the crabs have few natural predators -- something the researchers are hoping to change.

- Crab-eaters -

Launched last year and funded by the Emilia-Romagna region, the "Octo-Blu" project seeks to increase octopus numbers as a counterweight to the hard-shelled invaders.

The team breeds octopus hatchlings in white water tanks at a lab in the port town of Cesenatico.

When ready, the tiny invertebrates are scooped out by the thousands into a large plastic bag and taken out to sea, sometimes using Sanulli's rugged blue fishing boat.

The hatchlings are then released near underwater reefs where the group has laid cement-and-clay artificial dens to help the octopuses thrive.

Some 80,000 have been let out since June, an amount the research team is seeking to double by the end of August, hoping to see a few grow into fully developed octopuses.

"The idea is to establish a small community close to shore so that it can better combat the spread of the blue crab," said Casalini, an aquaculture technician.

The project has some clear drawbacks.

The common octopus is not prone to live in the sandy, warm waters typical of the lagoon areas where the blue crab is making the most damage, making its potential impact there negligible -- something the researchers are well aware of.

Other experts have suggested that seabass could be more effective at crab-fighting and the Bologna University team is also looking at eels, which are avid eaters of crustacean eggs, to complement the octopus's efforts.

Yet, if replicated, the pilot could still help limit blue crab numbers and the related impact on the Adriatic coast's marine environment, Casalini said.

"Blue crabs have an incredible reproductive potential and fertility rate," said Pietro Emmanuele, another University of Bologna researcher, noting a single crab lays millions of eggs, most of which hatch.

Although only some hatchlings reach adulthood, were an octopus to catch even a single female, it would make a difference, he said.

M.Saito--JT