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Marine heatwaves reshape British seas

scienceAug 17, 202613199

Skipper Kurt Lander reported an unusual surge of sunfish in the English Channel off Brighton this summer, part of a broader increase in warm-water visitors linked to marine heatwaves. The Met Office labelled last year’s conditions “exceptional,” with some parts of British waters experiencing heatwave conditions for three-quarters of the year, and 2026 is already showing similar warming. Researchers including Dr Zoe Jacobs at the National Oceanography Centre say colder-water species have shifted north and are now thriving in Scotland, while southern coasts see far fewer cod, Lander says he used to catch a couple of hundred cod a year but now lands one or two at most in summer. Divers such as Gio Reale report the near-disappearance of the small spotted catshark from shallow waters after seawater warmed from its preferred 16, 17C to about 20C, and reports show common octopuses have bloomed in Devon and Cornwall since January last year. The octopus boom has disrupted crab and lobster fisheries and prompted some boats to switch target species, with octopus catches soaring in 2026. The State of the South-West Seas report also notes sardines and anchovies are doing well, indicating a wider reorganization of species and fisheries along Britain’s coastline.

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