The brisk sea air whipped off the ropes as the diesel engine hummed in the background. Empty shellfish pots were pulled up one by one from the fishing boat, revealing remnants of crab and lobster claws and carapaces. But something unusual caught the attention of the fishermen – a squirming orange body surrounded by a tangle of tentacles.
As more pots were brought up, it became clear that a bloom of common octopus (Octopus vulgaris) had taken over the waters off the south coasts of Devon and Cornwall. This was a rare sight, as the common octopus is not typically found in British waters. The last time such an event occurred was 75 years ago.
Commercial catches of common octopus in 2025 were significantly higher than the annual average, indicating a sudden surge in population. A new report has delved into the history, causes, and consequences of these octopus blooms.
The common octopus has a short lifespan, with females dying after their eggs hatch and males dying after breeding. This makes them highly sensitive to environmental changes. The blooms are believed to be triggered by sustained periods of unusual warmth in the ocean and atmosphere, known as “marine heatwaves.”
These warm conditions, coupled with low salinity in coastal waters, create ideal breeding grounds for octopus populations. The influx of fresher water from major rivers like the Loire in France or easterly winds over the Channel can transport octopus larvae across the waters, leading to population explosions.
Despite the initial shock to the local fishing industry, fishermen quickly adapted to the octopus influx by targeting them for export. The lucrative market for octopus resulted in substantial earnings for some boats. However, concerns arose as octopus catches declined in August, alongside a significant drop in other shellfish fisheries.
Looking ahead, sustainable practices will be crucial to ensure the long-term survival of the common octopus population. With climate change likely to continue driving environmental shifts, it is essential to balance commercial interests with conservation efforts. Diversification of fishing opportunities and ethical practices will be key to maintaining a healthy marine ecosystem for both fishermen and marine life alike.
