Brown crabs are fascinated by underwater power cables to renewable energy sources, researchers have found.
The cables emit an electromagnetic field that causes them to sit still, leading to biological changes that could lead to greater risk of infection, according to a study.
Researchers are concerned about the decline in activity levels because it means crabs spend less time looking for food or looking for a spouse.
Their reduced movement also leads to changes in the creatures’ sugar metabolism, which means that they store more sugar and produce less lactate, just like humans.
Kevin Scott at St Abbs Marine Station said exposure to higher levels of electromagnetic field strength altered the number of blood cells in the crabs’ bodies.
“This can have a number of consequences, such as making them more susceptible to bacterial infection,” he said.
Offshore wind farms that require extensive submarine cables are being installed and planned around the coast of Scotland, and researchers fear they could destabilize the country’s brown crab population if no precautions are taken.
Changes in the species’ behavior could affect fisheries markets, as crabs are Britain’s second most valuable catch of crustaceans and the most valuable coastal catch, analysts say.
Alastair Lyndon, from Heriot-Watt University, said brown male crabs usually migrate up the east coast to Scotland.
“If miles of submarine cables turn out to be too hard to resist, they will remain stuck,” he said.
“This could mean we have a build-up of male crabs in the south of Scotland and a shortage of them in the north-east and islands, where they are incredibly important to fishermen’s livelihoods and local economies.”
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He suggested burying the cables in the seabed, but acknowledged that this could be expensive and would make maintenance more difficult – or even impossible in some situations.
“We need to explore further technical solutions so that we do not create negative environmental effects while trying to reduce our energy supply,” he added.
The study included 60 brown crabs at St Abbs Marine Station on the Scottish borders.
The magnetic field attracts the crabs when it is at a strength of 500 microteslas and above, which is about 5% of the strength of a refrigerator door magnet.