Shark Defenders

Do magnets repel sharks? When MythBusters, a Discovery Channel program that tests all manner of myths, rumors, and legends, took up the question last summer, the show’s hosts seemed inclined at first to confirm the theory. But in the end, they declared the myth busted.

Craig O’Connell (CAS’06) thinks they were mistaken. He and his research colleagues have submitted a rebuttal of the show’s findings, hopeful MythBusters will revisit the topic.

O’Connell is a researcher with SharkDefense Technologies, a small company working to develop shark repellents. Since he graduated from the CAS marine biology program, he’s been testing his theory that magnets can repel sharks, and he’s convinced he’s onto something.

You might expect that O’Connell is developing shark repellents to protect people from shark attacks, but his actual goal is protecting sharks from people. Scientists estimate that humans kill 100 million sharks every year, putting many shark species in danger of extinction. O’Connell hopes his research with magnets will provide shark conservationists with an inexpensive way to reduce shark deaths by keeping sharks away from beaches and fishing lines.

Shark conservation has been O’Connell’s passion since his junior year, when he spent a semester in Ecuador with the Tropical Ecology Program. “We made a stop in Ecuador’s coastal region, and we saw all these fish markets,” he says, “and I noticed the fishermen were catching a lot of sharks.”

It wasn’t clear whether the sharks were being caught accidentally as fishermen targeted other species — known as bycatch in the fishing industry — or if fishermen were intentionally catching sharks to sell their fins on the black market. O’Connell began a daily tally of dead sharks discarded on the beach near the markets. The number of carcasses — most of them finless — was shocking, he says, and ignited his desire to save sharks.

The idea that magnets could play a part in shark conservation came to O’Connell after he learned that sharks have special sensing organs called ampullae of Lorenzini that allow them to detect electrical fields. Sharks use this unique sense to locate prey, and some scientists believe they also use it to navigate by sensing variations in the Earth’s magnetic field. If sharks can sense the weak geomagnetic field, could a strong magnet startle a shark and frighten it into keeping its distance?

O’Connell’s first opportunity to test shark reactions to magnets came soon after graduation, when he landed a two-month volunteer research position at the Bimini Biological Field Station (known as Sharklab) in the Bahamas. When he got there, he found a group of researchers from SharkDefense Technologies also beginning to experiment with magnets. “They had just come up with the idea before I got to Bimini,” he says. “It was an amazing coincidence.”

O’Connell joined the SharkDefense team, helping design and conduct experiments. After he moved to South Carolina for graduate school, he continued to visit the lab every couple of months to help out.

“What we’ve found so far is incredible,” he says. The researchers have added magnets to netting used to create shark fences, and in some experiments they’ve seen a 95 percent reduction in the sharks entering through holes in the netting. They’ve also placed magnets above hooks on long fishing lines, he says, “and we’ve reduced shark catch by 50 percent.”

The SharkDefense researchers are still refining their understanding of how various magnets affect different species. Their research indicates, for example, that ceramic magnets are fairly reliable shark repellents, while super-strong rare earth magnets are not. This, they believe, is where MythBusters went wrong. The hosts of MythBusters started their experiments with ceramic magnets and then switched to rare earth magnets, which O’Connell believes are so strong that they simply overwhelm sharks’ senses.

O’Connell is optimistic that his research will yield reliable magnetic shark repellents within four or five years. “The sooner the better,” he says, “so we can save these sharks.”

This article originally appeared in the spring 2009 issue of arts&sciences magazine.