Mesmerised brown crabs ‘attracted to’ undersea cables

Scientists have discovered that underwater power cables can mesmerize brown crabs and trigger biological changes that could impact their migration patterns.
The electromagnetic field created by the cables for offshore renewable energies attracts crabs to their location and makes them stay there.

An investigation of 60 brown crabs from the St Abbs marine station in Scotland Borders revealed that electromagnetism levels were higher in crabs than previously thought. This caused cell changes and affected their blood cells.

Alastair Lyndon is an associate professor at Heriot-Watt University's centre for marine biology, diversity and biodiversity. He said that underwater cables emit an electromagnetic field. The crabs will sit still if the magnet is at 500 microteslas or more.

This is not an issue by itself. They are not looking for food or mates if they're not moving. Changes in activity can also lead to changes in sugar metabolism. They store more sugar and produce less milk, just like humans.

For the experiment, the researchers used a marine station purpose-built aquarium lab. Kevin Scott, manager at St Abbs, stated that the aquarium lab was entirely made of non-metallic materials. This means that there is very little electromagnetic interference.

Our research showed that higher levels of electromagnetic fields strength had a significant impact on the number of blood cell in the bodies of crabs.

This could lead to a variety of problems, including making the patient more vulnerable to bacterial infections.

The team warned that changing species behavior could impact fishing markets as crabs are both the UK's most valuable crustacean catch, and its most valuable inshore catch.

Numerous offshore wind farms have been installed around Scotland's coast. This requires extensive underwater cabling. Researchers also believe that they could destabilise the brown crab population of Scotland.

Lyndon stated: Male brown crabs migrate along the east coast of Scotland. They will stay put if miles of underwater cabling is too much for them to bear.

This could indicate that there is a high concentration of male crabs in Scotland's south, but a low number of females on the islands and north-east. These crabs are vital for local economies and fishermen's livelihoods.

One solution was to bury cables on the seafloor, but this can be costly and difficult to maintain, so it is not feasible in all locations.

Lyndon said: We must investigate technical solutions to ensure that we don't create negative environmental effects when trying to decarbonise the energy supply.

The Journal of Marine Science and Engineering published the study.

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