Exceptionally high sightings of one of the world's most intelligent invertebrates this past summer have led to the designation of 2025 as the octopus's year in an annual review of Britain’s seas.
A Confluence of Factors Driving a Surge
An unusually warm winter followed by an exceptionally warm spring catalyzed a massive influx of Mediterranean octopuses to settle along the shores from Cornwall to Devon, spanning the Cornish and Devonian coasts.
“The volume of octopuses caught was roughly thirteen times what we would usually anticipate in Cornish waters,” commented a marine life specialist. “When we added up the numbers, approximately 233,000 octopuses were present in these waters this year – representing a massive jump from what is typical.”
The common octopus is indigenous to these waters but ordinarily in such small numbers it is seldom observed. A sudden increase is caused by a combination of gentle winter conditions and a warm breeding season. Such favorable circumstances meant more larvae, maybe aided by significant populations of other marine life noted in recent years.
A Historic Event
Previously, an octopus bloom this significant was recorded in the mid-20th century, with archival data indicating the last bloom prior to that happened in 1900.
The huge numbers of octopuses meant they could be readily observed in nearshore environments for the first time in living memory. Video footage show octopuses congregating together – unlike their typical solitary behavior – and ambulating along the bottom on their tentacle tips. One creature was even recorded reaching for submarine recording equipment.
“The first time I dived there this year I saw five octopuses,” the specialist continued. “They are large specimens. There are two types in UK waters. The curled octopus is quite small, the size of a ball, but these newcomers can be with a span of 1.5 meters.”
Future Prospects and Other Surprises
A second gentle winter heading into next year suggests the potential a second bloom in 2026, because historically, under these conditions, the blooms have repeated for two consecutive years.
“But, it's improbable, from previous blooms, that it will go on for a long time,” they stated. “But the sea keeps giving us surprises currently so it’s a very uncertain scenario.”
The annual review also celebrated further encouraging coastal sightings around the UK coastline, including:
- Unprecedented numbers of grey seals seen in one northern region.
- Exceptional populations of puffins on Skomer.
- A first-ever sighting of the *Capellinia fustifera* nudibranch in Yorkshire, usually found in the south-west.
- A variable blenny found off the coast of Sussex for the inaugural time.
A Note of Caution
The year had its low points, however. “The year was bookended by ecological challenges,” said a head of marine conservation. “A major tanker collision in the North Sea and a spill of industrial pellets off the southern coast highlighted ongoing threats. Staff and volunteers are working tirelessly to protect and restore our coasts.”
