Key Takeaways
- 2025 has been declared "the year of the octopus" due to record numbers of sightings along England’s south coast
- A mild winter and warm spring led to an unprecedented bloom of Mediterranean octopuses, with approximately 233,000 caught in UK waters
- The last time an octopus bloom of this size was recorded was in 1950, with the previous bloom occurring in 1900
- Other notable wildlife sightings include record numbers of grey seals and puffins, as well as unusual species such as the Capellinia fustifera sea slug and variable blenny
- Environmental disasters, including a North Sea tanker collision and the release of biobeads off the Sussex coast, highlight the need for continued conservation efforts
Introduction to the Octopus Bloom
Record numbers of sightings of one of the world’s most intelligent invertebrates, the octopus, have led the Wildlife Trusts to declare 2025 "the year of the octopus" in its annual review of Britain’s seas. A mild winter followed by an exceptionally warm spring prompted unprecedented numbers of Mediterranean octopuses to take up residence along England’s south coast, from Penzance in Cornwall to south Devon. This sudden increase in population, known as a bloom, is caused by a combination of favorable weather conditions that allowed more larvae to survive and thrive.
The Scale of the Bloom
According to Matt Slater, a marine conservation officer at Cornwall Wildlife Trust, the scale of the catch recorded by local fishers was approximately 13 times what would normally be expected in Cornish waters. When the numbers were added up, approximately 233,000 octopuses were caught in UK waters this year, a huge increase from what would normally be expected. The common or Mediterranean octopus, Octopus vulgaris, is native to UK waters but ordinarily in such small numbers that it is rarely seen. The ideal conditions meant that more of the larvae were likely to survive, possibly in part fueled by the large numbers of spider crabs that have also been recorded along the south coast in recent years.
Historical Context
The last time an octopus bloom of this size was recorded was in 1950, with records from the UK’s Marine Biological Association showing the last bloom recorded prior to that was in 1900. The huge numbers of octopuses along the south coast meant they could be easily spotted in shallow waters for the first time in recent history. Video footage from divers shows octopuses gathering in groups, which is unusual behavior for these typically solitary creatures, as well as "walking" along the seabed on the tips of their limbs. One was even filmed grabbing at an underwater camera.
Implications for Future Blooms
Another mild winter going into 2026 meant it was possible there could be a second bloom next year, said Slater, because historically, under these conditions, the blooms have repeated themselves for two consecutive years. However, it is unlikely that the bloom will continue for an extended period, based on past events. The sea keeps giving us surprises, so it’s an unpredictable situation. The Wildlife Trusts noted some of the other "surprises, successes, and joyful moments" around the UK coastline, including a record number of grey seals observed by the Cumbria Wildlife Trust, as well as record numbers of puffins on Skomer, an island off the coast of Wales famed for the birds.
Other Notable Sightings
Other wildlife was recorded in unusual places, including a volunteer with Shoresearch, the Wildlife Trusts’ national citizen science survey program, who recorded the first Capellinia fustifera sea slug in Yorkshire, a 12mm mollusc that resembles a gnarly root vegetable and is usually found in the south-west. In addition, a variable blenny, a Mediterranean fish, was discovered off the coast of Sussex for the first time, with populations previously limited to the West Country. These sightings highlight the dynamic nature of the UK’s marine ecosystem and the importance of continued monitoring and conservation efforts.
Environmental Concerns
Not everything was good news, though. The year was bookended by environmental disasters, including a North Sea tanker collision in March and the release of tonnes of biobeads off the Sussex coast in November. These incidents highlight the need for continued conservation efforts to protect and restore the UK’s shorelines. The Wildlife Trusts staff and volunteers are making huge efforts to address these issues and promote the health of the marine ecosystem. Despite the challenges, the record numbers of octopuses and other wildlife sightings offer a sense of hope and wonder, and a reminder of the importance of preserving the natural world for future generations.