Climate change sees octopus blooming in the UK
The octopus lifestyle of ‘live fast, die young and make lots of babies’ mean their populations respond quickly to a changing environment. How fisheries respond remains to be seen
Climate change is reshaping the ocean. In the UK, cold-water species such as cod, pollack, and haddock have declined while blue sharks, conger eels, and comber are becoming more common. Bluefin tuna has been arriving in increasing numbers. And then there are the octopus.
Historically, common octopus, Octopus vulgaris, have not been at all common in the UK. That changed in 2025. Divers along the southwest coast of the UK started reporting more octopus than ever and fishers catching them in unprecedented numbers.
Octopus blooms are somewhat of a feature of the species, whose lifestyle could be described as live fast, die young, make lots of babies. Their populations respond quickly to the environment. A combination of warmer waters and bountiful food can make for an abundance of octopus.
Waters around the UK have been warming steadily with climate change, and for the past few years, parts of the southwest have been “almost constantly in a marine heatwave state,” said Dr Bryce Stewart, a marine ecologist and fisheries biologist at the Marine Biological Association in the UK. “It’s been consistently very, very warm for a long time.”
While warming waters along the south coast have almost certainly played a key role, it’s not the whole story. Researchers from Plymouth Marine Laboratory discovered that octopus larvae likely came into the UK from spawning grounds in the Channel Islands thanks to favourable currents.
This is not the first time octopus have bloomed in the UK, but previous events were short-lived. With consistently warmer waters, octopus now breeding in the UK, and sightings further north, “I think the octopus are here to stay now in much higher levels than they have been in the past,” said Stewart.
For divers and snorkellers delighted to see octopus, this may be good news. For some fishers, the picture is more complicated.
Octopus are voracious eaters of crabs, scallops, and lobsters. Although scallops should also do well in warmer waters, early indications suggest that in some scallop grounds where octopus are abundant, scallop numbers have declined substantially. Even if the octopus are fished out or the bloom recedes, those populations may not recover, or at least not to the same levels as before.
Rather than treating octopus as a short-term event, Stewart said there is growing recognition that they may need to be managed as part of the southwest’s fisheries. In Brittany, where octopus blooms began in 2021 and have since fluctuated, managers have introduced measures including permits, a closed season, and some gear restrictions. The octopus have become, as Stewart put it, “part of the mix of fisheries.”
Indeed, for some UK crab and lobster fishers who use pots, octopus could become an opportunity. “They basically can use the same gear,” Stewart explained, adding that some fishers are already targeting them.
But opportunity depends on where you fish. Octopus are not everywhere. One fisher may catch more in a single haul than they have seen in their entire life. A few hundred metres away, another catches none. Unfortunately for that fisher, that doesn’t necessarily mean more crabs or lobster. “I hear stories like one guy put out 150 pots and he got two crabs,” said Stewart. “You can't make a living out of that.”
Scallop fishers may also find it hard to adapt. Most scallops in the UK are caught by dredging. Dredgers don’t catch octopus, so “their real only option would be to switch to beam trawling, but that’s a major investment in gear,” says Stewart.
What happens next will depend partly on how the fishery is managed, but also on the wider ecosystem. Octopus are predators, but they are also prey, with seals, sharks, conger eels, and dolphins all feeding on them. Underpinning all of it is a climate and ocean that is still changing. Whether the octopus thrive, retreat, or become a permanent fixture of UK waters is one question. How fisheries respond is another.
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Image: Common Octopus. Credit: Shutterstock
