A significant marine heatwave, causing sea temperatures to spike up to 5 degrees Celsius above normal, has led to an unprecedented surge in octopus numbers in British waters. This phenomenon has resulted in exceptionally large catches for fishermen in Cornwall and Devon, with some reporting weekly profits exceeding £20,000.
The population of octopuses is now at its highest level in 75 years, with catches in the first five months of this year already surpassing the total for the previous year. Fishermen in Brixham recently landed approximately 200 tons of octopus in a single week.
Impact on Fisheries
While the octopus boom has benefited some segments of the fishing industry, it has also disrupted traditional fisheries. Key species for British consumers, such as cod and haddock, are migrating northward to escape the warming waters. Octopuses are also preying on lobsters and crabs, which are valuable catches in the South West of England. To protect these species, Cornwall has enacted an emergency bylaw prohibiting larger vessels from using pots that could inadvertently trap and expose lobsters and crabs to octopus predation.
Octopus meat is not a primary delicacy in Britain, leading to a surplus in supply and a drop in consumer prices. Consequently, much of the catch is being exported to European countries, like Spain, where it is a prized dish.
Professor Matt Frost of the Plymouth Marine Laboratory noted that while the arrival of new species can be scientifically interesting, the warming seas present negative consequences. "We're seeing a decline in the numbers of cod and other key species… you're also getting other species that could displace native species," he told the BBC, warning of potential disease introduction and other ecological problems.
Causes and Wider Trends
The current marine heatwave is most intense off the coasts of southern and eastern England. It is attributed to "heat domes"—high-pressure systems that trap hot air—and the long-term effects of climate change-driven ocean warming. This event coincides with the official declaration of an El Niño phenomenon in the Pacific Ocean, which is expected to contribute to rising global temperatures.
While a "Super El Niño" has been predicted for later this year, its meteorological effects on the UK typically lag, with impacts unlikely until 2027, according to climate researcher Nuala Burnett. In other parts of Europe, rising sea temperatures have also led to an increase in foreign species, including the silver-cheeked pufferfish, known for its powerful bite, which has been sighted in greater numbers off the coasts of Greece, Spain, Italy, and Turkey.
The UK's seas have been warming since the 1980s due to global warming, and extreme temperature spikes can severely damage marine ecosystems, causing die-offs in seagrass, shellfish, and other species. Experts predict that marine heatwave conditions could become the norm by the mid-to-late century if greenhouse gas emissions are not reduced.