Why is the Atlantic Ocean invaded by octopus?

There has been a massive presence of octopus since this summer on the Atlantic coast, unheard of for several decades. Until very recently, fishermen only landed around 100 tonnes of octopus per year from their boats. Also, seeing this animal on the fishmongers’ stalls, next to bars, sardines, and scallops, was quite anecdotal. But since the start of 2021, these fishermen have landed ten to fifty times more than usual, depending on the location, especially in Brittany. A reappearance which remains very mysterious because the octopus had disappeared from the Atlantic since the beginning of the 1960s, according to the French Research Institute for the Exploitation of the Sea (Ifremer) following the very cold winter of 1962-1963.

Is it because of the warming of the Atlantic? It is a track mentioned by scientists. Indeed, the waters of the Atlantic have warmed by 0.8 ° C in the space of forty years, confirmed Pascal Lorance, biologist at Ifremer in Nantes. But since octopuses were already abundantly present in Brittany until the beginning of the 1960s, in a cold Atlantic therefore, this explanation is not enough.

The octopus is also benefiting from the decline of some of its predators. In any case, the sudden return of this octopus to the Atlantic shows how sensitive marine ecosystems are. Certain large variations in population sometimes seem surprising. This has already happened for anchovy populations, for example, in the Bay of Biscay. This return of the octopus is good news for ecosystems in the Atlantic because it is never a bad thing to see the resurgence of species that had almost disappeared. For fishermen it is also a godsend, because the price of octopus fluctuates around seven euros per kilo, with buyers in France and Spain or in Portugal. But if these octopuses become too numerous, beware of scallops and the crustaceans they eat.

Because these cephalopods, at the same time, intelligent and voracious, are able to recover the cakes, lobsters and lobsters by using themselves directly in the fishing traps. The mysterious return of the octopus to Brittany could in any case see rapid twists and turns. The lifespan of the octopus is indeed very short. It lives on average two years and it reproduces only once. If the conditions are no longer favorable, it could therefore once again be more discreet from 2024.