A record number of octopuses, first observed off the south-west coast of England last year, have now spread as far as Scotland and Wales, significantly impacting the fishing industry and marine ecosystem, according to a new study.
Unprecedented Spread
The surge in sightings of one of the world's most intelligent invertebrates began in 2025 off the south coast of Devon and Cornwall. Now, scientific surveys, underwater monitoring, and observations from recreational divers and snorkellers reveal that octopuses have expanded along the north coasts of Devon and Cornwall, with sightings in Wales, Dorset, East Sussex, and Scotland.
Bryce Stewart, a senior researcher at the Marine Biological Association and lead author of the study, described the phenomenon as extraordinary. 'We have had blooms before, but everything I am seeing tells me this is the biggest bloom we have seen; it is quite different,' he said.
Warming Waters Driving the Bloom
The common or Mediterranean octopus (Octopus vulgaris) is native to UK waters but usually exists in such small numbers that it is rarely seen. The sudden population increase, or bloom, results from a mild winter followed by a warm spring breeding season. Researchers link the surging numbers to warming seas and broader environmental changes. 'Now we have warmer waters much more suited to these animals, we are seeing a huge increase in numbers,' Stewart added.
Mixed Impact on Fishing Industry
The bloom has brought mixed fortunes for fishers. Those relying on traditional shellfish have suffered as octopuses, highly effective predators, target crabs and lobsters, often from fishers' pots. However, others have benefited from record octopus hauls. The octopus catch surged by 7,700% in 2025, with a record 100 tonnes sold in a single day at Brixham market in Devon. 'Some fishermen have had to sell their boats because of the impact on crab and lobster populations, while others are doing extremely well,' Stewart noted.
Ecosystem Upheaval
The influx of octopuses is also disrupting the marine ecosystem. Besides preying on shellfish and some fish, octopuses provide food for seals, conger eels, and rare Risso's dolphins. 'It is a shake-up of the whole ecosystem,' Stewart said. The public has shown growing interest, with hundreds of divers and snorkellers assisting scientists in surveying the burgeoning octopus population.
