Marine conservationists have declared 2025 the "year of the octopus" after recording the highest numbers of the eight-legged creatures in British waters since the 1950s.
The Wildlife Trust's annual report states that rising sea temperatures and an unusually warm breeding season led to a record number of sightings of the common octopus, or octopus vulgaris, particularly off the coasts of south Cornwall and Devon.
A 'Flabbergasting' Marine Boom
The charity said it was left "flabbergasted" by the "incredible" numbers observed. While native to UK seas, these invertebrates are typically seen in such small numbers that sightings are rare. This year, however, they were filmed extensively, exhibiting behaviours like walking on the seabed, cleaning themselves, mating, and even investigating underwater cameras.
Matt Slater, marine conservation officer at Cornwall Wildlife Trust, revealed the scale of the increase, telling The Guardian that local fishers in Cornwall caught around 233,000 octopuses this year. This figure is approximately thirteen times the usual annual catch.
Warming Seas Drive Population Surge
Experts attribute this population explosion, or "bloom," to exceptionally mild conditions. A warmer breeding season increases the survival rate of octopus larvae. The Trust confirmed that a surge of this magnitude has not been documented since 1950.
With the World Meteorological Organisation forecasting continued rises in global temperatures, the charity expects 2026 to bring even higher numbers of octopuses in UK seas. "Octopus eggs are surviving our warming winters so we are likely to see a regular occurrence of octopus blooms in future years," their report stated.
This shift will require fisheries to adapt, as octopuses are voracious predators of lobsters, crabs, and shellfish.
Other Remarkable Marine Discoveries
The annual report also highlighted several other significant finds in UK waters during 2025:
- The first UK record of a pink-orange Spurilla neapolitana sea slug, nicknamed the "hair curler," was made in Cornwall. Previously, sightings of this nudibranch, usually resident in the Caribbean and Mediterranean, had only been recorded as far north as Brest, France.
- One of the world's rarest sharks, a critically endangered angelshark, was spotted in Cardigan Bay, Wales. It was the first time the species had been caught on underwater cameras there in four years.
Ruth Williams, head of marine at The Wildlife Trusts, noted that a year "bookended" by environmental disasters, like the North Sea tanker collision in March, still held "moments of joy and wonder."
"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," she said. "They’ve also been flabbergasted by the incredible numbers of octopuses recorded this year."
