2025 Proclaimed 'The Octopus Year' Off Britain's South Coast.

Record-breaking sightings of one of the world's most intelligent invertebrates over the summer months have resulted in the designation of 2025 as “the year of the octopus” in a seasonal assessment of the nation's marine environment.

A Confluence of Factors Leading to an Explosion

An unusually warm winter and then an exceptionally warm spring prompted a massive influx of common octopuses (*Octopus vulgaris*) to establish themselves along the shores from Cornwall to Devon, across the southwestern peninsula.

“The volume of octopuses caught was of the order of about thirteen times what we would typically see in Cornish waters,” stated an ocean conservation expert. “When we added up the numbers, approximately 233,000 octopuses were present in UK waters this year – which is a significant rise from the norm.”

The Mediterranean octopus is found in British seas but typically so rare it is rarely seen. A sudden increase is caused by the dual effect of a mild winter and a warm breeding season. Such favorable circumstances meant increased juvenile survival, possibly in part fuelled by large numbers of spider crabs also recorded.

A Historic Event

Previously, an octopus bloom this significant was observed in the mid-20th century, with archival data indicating the last bloom prior to that was in 1900.

The remarkable abundance of octopuses meant they could be frequently seen in nearshore environments for the first time in recent history. Underwater recordings show octopuses congregating together – contrary to their normally lone nature – and ambulating along the ocean floor on the tips of their limbs. One creature was even recorded reaching for submarine recording equipment.

“During a first dive there this year I saw multiple octopuses,” they noted. “And these are big. We have two species in UK waters. The curled octopus is smaller, football-sized, but these common octopuses can be with a span of 1.5 meters.”

Future Prospects and Other Surprises

A second gentle winter going into 2026 suggests the potential a repeat event the following year, because historically, under these conditions, populations have surged again for two years running.

“But, it's improbable, looking at history, that it will persist indefinitely,” they stated. “But the sea keeps giving us surprises these days so it’s hard to forecast.”

The assessment also noted additional positive marine news along the coast, including:

• A record number of gray seals seen in Cumbria.
• Record numbers of puffins on Skomer.
• A first-ever sighting of a rare sea slug in Yorkshire, usually found in the south-west.
• A Mediterranean fish species discovered off the coast of a southern county for the first time.

Not All Positive News

Challenges were also present, however. “The calendar year was marked by ecological challenges,” said a head of marine conservation. “A significant shipping incident in the North Sea and an accidental discharge of tonnes of plastic biobeads off the southern coast highlighted ongoing threats. Dedicated individuals are putting in immense work to protect and restore our coasts.”