Conservationists and marine enthusiasts alike are calling 2025 the “year of the octopus,” as record numbers of octopus vulgaris—the common or Mediterranean octopus—have been spotted along the south coast of England, particularly in Cornwall and Devon. This remarkable surge marks the highest octopus numbers seen in British waters since the 1950s, according to The Wildlife Trusts’ annual marine review, and has left scientists both amazed and concerned about the broader implications for the region’s marine ecosystem.
Throughout the year, thousands of octopuses have been seen “walking,” cleaning themselves, mating, and even grabbing at underwater cameras, with sightings up an astonishing 1,500% from Penzance to South Devon compared to just two years ago, as reported by BBC and The Guardian. “When we added up the numbers, approximately 233,000 octopuses were caught in UK waters this year – that’s a huge increase from what you would normally expect,” said Matt Slater, a marine conservation officer at Cornwall Wildlife Trust, in an interview with The Guardian.
The unprecedented population boom, known as a ‘bloom’, is largely attributed to a combination of exceptionally mild winters and a warm breeding season, conditions that allowed octopus eggs and larvae to survive in far greater numbers than usual. The Wildlife Trusts emphasize that octopus numbers typically ebb and flow, but this year’s bloom is “unusually big”—the last event of this magnitude occurred in 1950. Official figures back up these observations: more than 1,200 tonnes of octopus were landed by fishermen in UK waters during the summer of 2025, a dramatic increase on previous years, according to government data cited by BBC News.
Experts believe that climate change, and the resulting rise in sea temperatures, is a key factor behind the octopus boom. The World Meteorological Organisation has predicted that global temperatures will continue to rise over the next five years, and The Wildlife Trusts warn that “octopus eggs are surviving our warming winters so we are likely to see a regular occurrence of octopus blooms in future years,” as stated in their annual report. The current mild winter could even trigger a second bloom in 2026, further increasing octopus numbers in UK seas.
But what does this mean for the wider marine environment and local industries? Octopuses are voracious predators, feeding mainly on shellfish such as lobsters, crabs, and scallops. Ruth Williams, head of marine at The Wildlife Trusts, told BBC’s Today programme, “They are having an impact on those (shellfish) species around our shores. And as a consequence, they will be having an impact on our fishing industry who target those species as well.” Indeed, government data shows that crab landings are down compared to previous years, though catches of lobster, crawfish, and scallops have remained stable so far.
The Wildlife Trusts suggest that fisheries may need to adapt to these changing conditions. “There are opportunities and our fishing industry are doing some research into that at the moment to try and evolve with the changing fisheries that we’re seeing as a result of climate change,” Williams added. The charity’s annual review also notes that octopuses were observed displaying a range of remarkable behaviors, including jet-propelling themselves, camouflaging to blend in with seaweed, and even “walking” underwater using two of their arms—a spectacle that left both divers and scientists “flabbergasted.”
While the octopus bloom has captured headlines, it is just one of several extraordinary marine events recorded in 2025. The Wildlife Trusts’ report highlights the first UK record of a pink-orange “hair curler” sea slug (Spurilla neapolitana) in Cornwall—a species usually found in the Caribbean and western Atlantic—and the first sighting of Capellinia fustifera sea slug in Yorkshire. One of the world’s rarest sharks, the critically endangered angelshark, was also spotted in Cardigan Bay, Wales, caught on underwater cameras for the first time in four years.
There was good news for seabirds as well. A record 46,000 puffins were counted on Skomer Island, Pembrokeshire, surpassing the previous record set in 2023. Conservation efforts on the Isle of Muck, led by Ulster Wildlife Trust, have also paid off, with the first signs of puffin breeding following the removal of invasive brown rats. Healthy transplanted seagrass off the Essex coast was another positive outcome, providing vital habitat for marine life.
However, the year was not without its challenges. The Wildlife Trusts’ review points out that 2025 was “bookended” by environmental disasters. In March, a collision between an oil tanker and a container ship in the North Sea resulted in a massive spill of plastic resin pellets, while in November, nearly 4.5 tonnes of bio-beads were released from a water treatment plant off the Sussex coast. These incidents, as reported by The Wildlife Trusts and BBC, underscore the ongoing threats facing UK marine environments, even as some species thrive.
Despite these setbacks, Ruth Williams remains optimistic. “Despite the year’s challenges, we’ve had moments of joy and wonder,” she said. “Our conservationists have celebrated successes such as the first signs of puffin breeding on the Isle of Muck and transplanted seagrass growing healthily off the Essex coast. They’ve also been flabbergasted by the incredible numbers of octopuses recorded this year.”
Looking ahead, scientists are keen to understand whether the octopus surge is a one-off event or the beginning of a new normal for UK waters. As Williams and others have noted, the answer will have significant implications for marine biodiversity, commercial fisheries, and the health of Britain’s coastal ecosystems. For now, the “year of the octopus” stands as a vivid reminder of just how rapidly our seas can change—and how closely those changes are tied to the shifting climate.
