A marine heatwave has driven a boom in octopus numbers off the coasts of Cornwall and Devon, with sea temperatures reported to be around 5C above normal. The surge matters because it has brought record profits for some South West fishermen while disrupting the wider UK fishing industry, as traditional catches shift and shellfish stocks come under pressure.

Some English fishermen are earning more than £20,000 a week, landing hauls of up to 20 tons, and octopus numbers are said to be at their highest in 75 years after rising from 2025 into 2026. However, cod and haddock are moving north towards cooler waters, and octopuses are preying on valuable lobsters and crabs, prompting Cornwall to introduce an emergency bylaw restricting larger vessels from potting for octopus. The article notes the trend coincides with Britain bracing for its longest heatwave in 50 years, with experts suggesting a possible "Super El Niño" could raise global temperatures, though its UK impact may not be felt until 2027. With octopus a niche choice for British diners, supply is far outstripping demand and consumer prices have fallen.