Some 150,000 baby common octopuses (Octopus vulgaris) have just been released into the waters off Italy’s Adriatic coast in one of Europe’s first pilot experiments to test whether the species can help control the invasive blue crab (Callinectes sapidus), which eats native shellfish and threatens the fishing industry and marine ecosystems. Two years ago, Oliviero Mordenti and Antonio Casalini, two aquaculture researchers at the University of Bologna, Italy, began to wonder whether octopuses offered a way to control blue crabs off the coast of Emilia-Romagna, a region of north-east Italy where damage caused by the blue crabs has cost the fishing industry £14.7 million since 2022. Invasive mink eradicated from parts of England by using scented traps Previous studies had identified the common octopus as a predator of the blue crab, backing up what local fishers had been seeing for a decade as populations of the Atlantic-native invasive species began to surge along Italian coasts.
However, octopuses tend to do better on rocky seabeds, while the Adriatic coast is rather sandy, which may help explain why octopus numbers there have been falling in recent decades. The regional government of Emilia-Romagna has installed artificial shelters for octopuses in an effort to reverse the decline. Under a research project co-financed by the regional government, Mordenti and Casalini caught eight common octopuses – four females and four males – from the Emilia-Romagna coast, transferred them to the laboratory and gave them about three months to acclimatise to their new surroundings.
Their tanks were carefully monitored and maintained under conditions designed to simulate those at sea. The researchers then arranged the octopuses into four breeding pairs and allowed them to mate and produce eggs. Earlier this week, the scientists released 150,000 millimetre-long, lab-raised larvae into the waters off the coastal towns of Cesenatico and Riccione.
They estimate that only 1 per cent will survive to adulthood. After hatching, octopuses start their lives as tiny, free-floating larvae known as paralarvae. They drift through the water and may be eaten by fish.
The hope is that a few will escape this fate and grow large enough to begin preying on blue crabs — a feat even small common octopuses weighing less than 800 grams are capable of, the researchers say. A popular idea suggests a link between big brains and a rich social life, but octopuses don’t fit the pattern, which suggests something else is going on “Our aim was to bolster the population of a native species already found naturally in the Adriatic,” says Casalini. But some scientists argue that this strategy needs more study.
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