Brown crabs are “mesmerised” by electromagnetism from underwater power cables laid around Scotland for offshore wind farms, a newly published study has found.
The edible crab Cancer pagurus displayed a clear attraction to the underwater cables, the study published in the Journal of Marine Science and Engineering has found.
Scientists at Edinburgh’s Heriot-Watt University focused on the behaviour of a group of about 60 crabs at St Abbs marine station on the Scottish borders.
They found the higher levels of electromagnetism emanating from the cables caused cellular changes affecting the crabs’ blood cells.
“Underwater cables emit an electromagnetic field. When it’s at a strength of 500 microteslas and above, which is about 5 per cent of the strength of a fridge door magnet, the crabs seem to be attracted to it and just sit still,” Alastair Lyndon of Heriot-Watt University said.
“If they’re not moving, they’re not foraging for food or seeking a mate. The change in activity levels also leads to changes in sugar metabolism,” he said.
“ They store more sugar and produce less lactate, just like humans.”
“The aquarium lab is composed entirely of non-metallic materials, which means there is minimal electromagnetic interference,” Kevin Scott of St Abbs marine station said.
“ We found that exposure to higher levels of electromagnetic field strength changed the number of blood cells in the crabs’ bodies. This could have a range of consequences, like making them more susceptible to bacterial infection.”
Brown crabs are Britain’s second most valuable crustacean, and the most valuable inshore, catch. The scientists say the findings show how fishing markets could be affected by the change in crab behaviour.
The researchers have called for further research to ensure extensive underwater cabling required for Scottish coast wind farms does not destabilise the brown crab population.
Lyndon pointed out that if male brown crabs stop migrating up the east coast of Scotland, due to the impact of cables, it could affect population levels in the north-east and off the islands – and, by extension, the livelihoods of inshore fishermen.
Burying cables could provide a solution, but it is regarded as costly and posing maintenance challenges.
“We need to investigate further technical solutions so that we don’t create negative environmental effects while trying to decarbonise our energy supply,”Lyndon said.
The full study in the Journal of Marine Science and Engineering can be read here.
