Will Muskeget cables affect sharks?

Data suggests some sharks are repelled and others drawn to marine cables.

Will Vineyard Wind's export cables affect sharks? One experts says they maybe attracted out of curiosity but wouldn't linger once they see the cables aren't food. — WikiMedia Commons

The export cables Vineyard Wind intends to bury in the Muskeget Channel have taken heat from local fishermen over the course of three hearings held by the Edgartown conservation commission. One of the main questions fishermen have posed is what effect the electromagnetic fields (EMFs) generated by the cables will have on sea life. Species-specific answers to those questions from Vineyard Wind and its consultant, Epsilon Associates, were relatively slim.

However, Ted Barton, one of Epsilon’s founders, said despite the 400-megawatt capacity of the cables, the radiated electromagnetism from the export cables, as measured in units called milliGauss, would be fairly low, less than a refrigerator magnet, even if the cables were exposed and unarmored. He went on to point out the cables will be buried beneath the seafloor and encased in armor, both of which diminish emitted EMF. 

Sharks are highly sensitive to EMF. Whether that poses a problem with regard to the cable is an unknown. An analysis of available data the Virginia Coastal Zone Management Program commissioned Virginia Commonwealth University to conduct, in light of fishermen’s concerns about impending wind turbine installations off the Virginia coast, revealed sharks are both “attracted” and “repelled” by undersea cables. 

The report made the following verbatim points:

  • Sharks and rays are 14,000 times more sensitive to EMF than bony fish.
  • Scientists have found evidence of EMF effects on multiple species of sharks and rays, including prey and predator detection and navigation issues.
  • Attraction to cables varies by species and the intensity of the emitted EMF.
  • Some species are attracted to the cables, while others are repelled.
  • Some species of sharks can detect buried cables up to 20 meters away.
  • Some species have been shown to attack exposed electrodes emitting EMF in some instances.
  • Sandy dogfish, Scyliorhinus canicula, were found to nonrandomly associate nearer to the cables when energized.

Laura McKay, Virginia Coastal Zone Management program manager, said Wednesday afternoon, “as we speak, they are laying a transmission cable off Virginia Beach.” McKay said the cable will serve two six-megawatt test turbines meant as a precursor to a large wind farm. Another cable will be laid for that farm. The cable is 25 miles from the beach, and is being buried three feet beneath the seabed. No shark studies have yet been conducted. Virginia Coastal Zone Management has so far only had studies done on sturgeon, she said. All the information in their EMF report comes from previously published data. 

White sharks are known to periodically inhabit the waters off Chappaquiddick, where the cable will be. South African white shark expert Chris Fallows, who has been free-diving with the huge fish for almost three decades, doesn’t put much credence into a potential threat from cables. “If there’s an attraction, it would be a very short-term basis,” he said. This would be because the shark would find no food source, he noted. At most, he suggested, cables might be a fleeting lure, a “curiosity factor.”

He said there are many undersea cables in places he dives in South Africa, and they haven’t “added or created an influx of sharks.”

In all his time diving, Fallows said, he never encountered an aggressive white shark anywhere in the world. 

James Sulikowski, who researches sharks at the University of New England, said sharks key in on a “very specific wavelength that’s centered around their prey … if the [cables are] within the range of what their prey are emitting, it could be a problem.” 

He went on to say, “Unless you know the range those things are emitting, you really can’t know how it will affect a shark.” Nevertheless, he didn’t deem the cables too threatening overall. “I would proceed with caution, but not expect [the cables] would have an impact,” he said.