Octopus Bloom off the Southwest UK: Key Findings for Commercial Fishermen

The final report on the common octopus (Octopus vulgaris) bloom in Southwest UK waters (Work Package 1) has been released, offering important insights into the 2025 event and its impact on the fishing industry, particularly for those targeting shellfish.

Summary of the 2025 Bloom and its Causes:

• The 2025 bloom of common octopus off the Southwest UK coast was confirmed as an exceptional event, comparable in scale to previous blooms in 1899-1900, 1932-33, and 1950-51.
• The total landings of O. vulgaris by the end of 2025 were almost 65 times higher than the annual average between 2017 and 2024.
• High abundance was generally seen from April to July 2025, peaking in May, with a distinct drop in August. However, some vessels again reported very large catches in November and December 2025.
• Environmental analysis consistently associated the 2025 bloom—and all historical blooms—with unusually warm sea and atmospheric temperatures during the peak year and the preceding year. This is thought to have increased breeding success, enhanced overwinter survival of juveniles, and led to rapid growth into adults.
• Modelling suggests that under the prevailing conditions, octopus larvae may have been transported from large blooms in the Channel Islands to the UK coast, potentially contributing to the UK increase.
• Fishermen's observations indicated that movements were a key factor, with reports of octopus moving from offshore to inshore waters as the season progressed.

Impact on the Fishing Industry:

• The bloom had a mixed effect on crab and lobster fishermen, the majority of the survey respondents.

• Negative Impact: 57.6% of crab and lobster fishermen surveyed reported a negative effect on their business between January and August 2025. Predation by octopus on brown crabs (Cancer pagurus), European lobsters (Homarus gammarus), and king scallops (Pecten maximus) in fishing gear and the natural environment was cited as the largest negative effect.
• Positive Impact: 27.3% of the same fishermen reported a positive effect, largely due to their ability to adapt and successfully target octopus instead of shellfish for a period.

• Landings data from ICES area 7e (the area of concentration for the bloom) for January to August 2025 showed significant declines in non-octopus shellfish landings compared to the average for the same period in 2021-2024:
• Brown crab landings dropped by 52%.
• King scallop landings dropped by 52%.
• European lobster landings dropped by 30%.

• Gear Type: Pots were by far the dominant gear used to land octopus, accounting for 68.2% (695 tonnes) of the total landed tonnage from January to August 2025, followed by beam trawls (33.7%, 367 tonnes).

Looking Ahead (Recommendations):

• The chance of the bloom continuing or reoccurring is considered high, given the trend of warmer-than-usual conditions due to climate change.
• Fishermen expressed a need for support to adapt, including:

• New or different gear, especially pots or traps specifically designed to catch octopus.
• Better market access for selling octopus.
• Increased provision of ice and appropriate fish boxes for octopus.
• More adaptable management regulations.

• An urgent investigation into the social and economic impact on affected fishing communities is recommended.
• Further research and monitoring are recommended, including expanding trawl and BRUV surveys, and acoustic tagging of common octopus in the English Channel to better understand any large-scale movement or migration.

You can red the full report from Plymouth Marine Science below or download it here: