Record numbers of sightings of one of the world’s most intelligent invertebrates over the summer have prompted the Wildlife Trusts to declare 2025 the “Year of the Octopus” in its annual review of Britain’s seas.
A mild winter followed by an exceptionally warm spring has driven unprecedented numbers of Mediterranean octopuses to take up residence along the southern coast of England, from Penzance in Cornwall to south Devon.
“The size of the catch [recorded by local fishers] Matt Slater, marine conservation officer at Cornwall Wildlife Trust, said: “It was about 13 times the size of what we would normally expect in Cornish waters. When we added up the numbers, almost 233,000 octopuses were caught in UK waters this year – that’s a significant increase on what you would normally expect.”
Common or Mediterranean octopus, Common octopusis native to UK waters, but is rarely seen in small numbers. The sudden increase in population – the bloom – results from a combination of a mild winter followed by a warm breeding season in the spring. Ideal conditions mean more common octopus larvae are likely to survive, perhaps fueled in part by the large numbers of spider crabs that have also been recorded along the south coast in recent years, Slater said.
The last time an octopus bloom of the size observed in 2025 was recorded was in 1950, with… Records from the Marine Biological Society of the United Kingdom It shows the last bloom recorded before that in 1900.
The huge numbers of octopuses along the southern coast mean they can be easily spotted in shallow waters for the first time in modern history. Video footage captured by divers shows octopuses congregating in groups – usually solitary – as well as “walking” along the sea floor on the tips of their limbs. One of them was photographed holding an underwater camera.
“The first time I dived off the Lizard Peninsula this year, I saw five octopuses,” Slater said. “And they’re big. There are two species of octopuses in UK waters. There’s the convoluted octopus, which is very small, about the size of a football, but these common octopuses can be up to a meter and a half across.”
Another mild winter until 2026 means there could be a second bloom next year, Slater said, because historically, under these conditions, blooms repeat the same two years in a row.
He added: “But based on past events, it is unlikely that this will continue for a long time.” “But the sea continues to present us with surprises at the moment, so it is a completely unpredictable situation.”
The Wildlife Trusts noted some other “surprises, successes and delightful moments” around the UK coast, including a record number of gray seals spotted by the Cumbria Wildlife Trust, as well as record numbers of puffins on Skomer Island, an island off the coast of Wales popular with the birds.
Other wildlife has been recorded in unusual places. A volunteer at Shoresearch, the Wildlife Trusts’ national citizen science survey program, recorded the first case Capelinia fostifera The Yorkshire sea slug, a 12mm-long mollusk that resembles a prickly root vegetable and is usually found in the southwest. In addition, there is the variable blenny fish, which is a Mediterranean fish. It was discovered off the coast of Sussex for the first time. The population was previously limited to the western country.
However, it wasn’t all good news. Ruth Williams, head of marine conservation at the Wildlife Trusts, said: “The year has been brought to an end by environmental disasters.” “[There was] An oil tanker collision in the North Sea in March and, in November, released tonnes of biobeads off the Sussex coast. Our Wildlife Trusts staff and volunteers go to great lengths to protect and restore our beaches.