Half a million octopuses in the Adriatic against the blue crab

Around half a million laboratory-reared young octopuses will be released in the waters off Riccione and Cesenatico during the second half of August. The operation forms part of the Octo-Blu project, run by the Emilia-Romagna region together with the Department of Veterinary Medical Sciences at the University of Bologna.

The target is the blue crab, a non-native species colonising the Mediterranean rapidly. The common octopus is one of its main natural predators, and laboratory studies have shown that even small individuals can subdue much larger crabs.

Brick dens on the seabed

The Adriatic seabed is mostly sandy, which makes it hard for octopuses to settle. To remedy that, local mussel farmers will place artificial brick dens made in the university laboratories.

The stated aim is not to eradicate the species, a task the organisers regard as beyond reach. Instead the intention is to harness natural predation to restore an ecological balance that has been disturbed.

The blue crab originates from the Atlantic coasts of the American continent. It reaches twenty centimetres across and is recognisable by the bluish colouring of its legs and the orange tips of the claws in females. The first sightings in the Mediterranean date from the 1950s.

Its spread depends on global maritime traffic. The larvae are drawn in along with the ballast water that stabilises large cargo ships, and in the destination ports the water is discharged together with the organisms it contains.

The damage falls mainly on aquaculture. The crab is omnivorous and equipped with powerful claws: it feeds on clams, mussels and oysters, but also on prawns, small fish and fry. Its proliferation has reduced the productivity of shellfish farms, particularly in the lagoons of the Po Delta.

Experts recall that biological control has to sit within a broader approach. In Turkey the creation of a commercial fishery using selective traps has turned the blue crab from an environmental problem into a food resource.

Invasive species are a familiar subject south of the Alps too. In 2026 the canton of Ticino set up monitoring plans and large-scale trapping against the Japanese beetle, to protect vineyards and crops.