The Times reports today (Oct 11, 2021) that undersea electricity cables cause brown crab to sit still. It seems that the electromagnetic field around the cables, which is about 5% of the power of a fridge door magnet, mesmerises them, and because they sit still, it damages their health.
If they are sitting still, they are not foraging for food or seeking out a mate. Their activity levels are dramatically reduced which leads to changes in their sugar metabolism. They store more sugar and produce less lactate which is what happens to humans apparently when they are enacted like this.
A study of about 60 brown crabs at St Abbs Marine Station in the Scottish Borders found that high levels of electromagnetism caused cellular changes which affected blood cells. In the study, they used an aquarium without any metallic materials so that there was minimal electromagnetic interference.
Kevin Scott 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.”
This health problem with crabs, a consequence of human commercial activity, could impact fishing markets as the crabs are the UK’s second most valuable crustacean catch. They are also the most valuable inshore catch.
It seems that the cables come from offshore wind farms, and more are planned. They require extensive underwater cabling. Researchers said that further work was needed to make sure that they did not destabilise Scotland’s crab population.
Alastair Lyndon from Heriot-Watt University, said that:
“Male brown crabs migrate up the east coast of Scotland. If miles of underwater cabling proved too difficult to resist, they’ll stay put. This could mean we have a build-up of male crabs in the south of Scotland, and a paucity of them in the North, East and Islands, where they are incredibly important for fishermen’s livelihoods and local economies.”
The solution, he said was to bury the cables on the seafloor which would obviously be far more expensive and maintenance would be more challenging. Also, it is not possible to bury cable in certain locations.
The study was published in the Journal of Marine Science and Engineering. The researchers don’t know why electromagnetic fields mesmerize crabs. Perhaps and alternative remedy would be to find out why and act upon that information. The response might be different to burying cables.
SOME MORE ON MARINE WILDLIFE: