While on a quest to create effective shark repellents, marine biologist Patrick Rice stumbled upon an unexpected type of shark "kryptonite." He found that rare earth elements, like samarium, create an electric current when they are submerged in salt water next to a shark fin. Fishing hooks made out of rare earth elements could repel sharks while still luring other types of fish.
Kryptonite for Sharks
Published: May 15, 2014
DAVID POGUE: Ah, is this your little kiddie pool where you bring the children to swim?
PATRICK RICE (Marine Biologist): This is our little tank here, where we have a couple little bonnet head sharks and a little nurse shark, in here.
DAVID POGUE: Rice was searching for the next great shark repellent, when he made an accidental discovery that looks like it'll be good news for both man and fish.
PATRICK RICE: We had sharks in a tank like this, and a pump broke on one of our tanks, and so, we were playing with these magnets, and we put the magnets down by the tank to go fix the pump, and when we put the magnet by the tank, the sharks took off.
DAVID POGUE: Somehow, the sharks inside the tank sensed the presence of magnets outside the tank, and when they did, they voted with their fins.
Patrick offers to demonstrate the weird repulsive effect. He hands me a case of super-strong magnets.
So this is, this is full of actual regular, old refrigerator…oh yeah, more than, more than refrigerator magnets.
PATRICK RICE: That's right, that's right.
DAVID POGUE: And you're saying that this will somehow repel the sharks?
Okay, here comes a little guy.
PATRICK RICE: That's a little nurse shark. It might work for him. Tell me when he gets over here.
DAVID POGUE: All right. Three, two, one.
Oh, my gosh. It's like you dropped that thing on his head.
PATRICK RICE: Yeah, you saw it, huh?
DAVID POGUE: Yeah, he's like, dun dun dun, wow! He, like, whipped out of there.
PATRICK RICE: Right. Right, right, exactly.
DAVID POGUE: The shark can't see the magnet, but it obviously feels the effect.
And it's not happy.
PATRICK RICE: One, two, three, now. Boom! You got him.
DAVID POGUE: Really?
PATRICK RICE: Yeah, you got him.
DAVID POGUE: That's crazy.
PATRICK RICE: Isn't it amazing?
DAVID POGUE: Patrick thought he could somehow use this effect to save sharks from being inadvertently caught by commercial fishermen, but there was, so to speak, a catch.
PATRICK RICE: We put the magnet right above the hook, on the line.
DAVID POGUE: Oh, okay.
PATRICK RICE: And what was happening was the hooks were swinging around and getting caught on the magnets.
DAVID POGUE: That would happen.
PATRICK RICE: So, it wasn't catching any sharks, but it wasn't catching anything else either.
DAVID POGUE: But he wasn't willing to give up. He decided he needed to find the weakest possible magnet that would still effect sharks.
The first step was to create a baseline for comparison, by exposing sharks to non-magnetic materials.
He offers to recreate his experiment.
You know, I don't have insurance for this.
PATRICK RICE: Be careful. It might be slippery.
DAVID POGUE: You're warning me about the slipperiness? Dude, there's three sharks in here!
PATRICK RICE: No, but they're nice.
DAVID POGUE: Okay, I just want to say, for the record, that I'm standing in a tank full of sharks.
PATRICK RICE: That's correct.
DAVID POGUE: This is like Jaws 7: The Kiddie Pool.
Step one: capture a shark.
Dude, you just caught a shark with your bare hands!
Then, flip the shark upside down, which induces a trance state called "tonic immobility." Once the shark is calm, we test its reaction to a piece of ordinary, non-magnetic lead.
Would you like me to just conk her on the head with this?
PATRICK RICE: Cover up her eyes.
DAVID POGUE: So it's not a visual thing.
Using a shield, to make sure that the shark can't see the metal, I bring it close.
PATRICK RICE: No reaction.
DAVID POGUE: None at all, as expected.
Next: a non-magnetic piece of samarium, a rare earth element. The expectation was that, because it's non-magnetic, there would be no reaction.
PATRICK RICE: She didn't like that at all.
DAVID POGUE: This is like kryptonite for sharks.
PATRICK RICE: Yes, it is.
DAVID POGUE: Wow, that's amazing. It just woke her up and drove her crazy.
PATRICK RICE: Yep.
DAVID POGUE: So the idea is you could make what out of this stuff?
PATRICK RICE: Well, the idea is that it's not magnetic, so we could potentially incorporate it into a fishing hook. And then you got something that repels sharks but doesn't have the magnetic properties, so it won't tangle the gear and stuff like that.
DAVID POGUE: The discovery that non-magnetic rare earths have a repellent effect on sharks was a complete fluke.
And it works with other rare earth metals as well. But why? What do sharks have against these particular elements?
PATRICK RICE: We believe it's creating a little electric shock.
DAVID POGUE: A little electric shock?
PATRICK RICE: Yeah, yeah.
DAVID POGUE: A shark shock?
PATRICK RICE: A shark shocker.
DAVID POGUE: Patrick demonstrates, using a beaker of seawater, a piece of samarium, a voltmeter and an actual shark fin.
(Singing) Bum bum, bum bum, bum bum, bum bum…
When he submerges the samarium and the shark fin in the seawater, an electric current flows.
Whoa! Oh, my god.
PATRICK RICE: That's almost a D-size battery.
DAVID POGUE: You're kid-…did we just make, in effect, a battery?
PATRICK RICE: Correct.
DAVID POGUE: As a group, the rare earths give up their outer electrons very easily. In the salt water, samarium atoms break free of the metal disk and give up one or more of their outer electrons. The atoms become positively charged and are attracted to the shark fin, which, like many biological materials, has a slight negative charge. The movement of the charged atoms creates an electric current.
Wow, that's some real juice flowing in there, just like in a battery.
It is like a battery, isn't it? It's a complete closed circuit, and the voltmeter's measuring that. That's pretty amazing.
PATRICK RICE: Yeah.
DAVID POGUE: But is the effect actually strong enough to put a shark off its meal?
PATRICK RICE: So we've just done our little test.
DAVID POGUE: There's one final experiment we can run to find out.
PATRICK RICE: What we're going to do now…
DAVID POGUE: Thank you.
PATRICK RICE: You're welcome.
DAVID POGUE: That was just for the blooper reel. We like to get some material…
As I was saying, there's one final experiment we can run to find out.
PATRICK RICE: What we're going to do here is a little experiment we've never done before.
DAVID POGUE: You haven't done this before?
PATRICK RICE: We haven't done this before.
DAVID POGUE: You waited until there was a national TV camera rolling?
There's a nine-foot lemon shark in this lagoon, and it's lunchtime.
Now for the test: we're going to suspend two identical pieces of tuna. One will hang below a piece of lead,—that's our control—the other under a piece of samarium.
PATRICK RICE: You go ahead and put it out there.
DAVID POGUE: Really?
PATRICK RICE: Yep.
DAVID POGUE: Lower her down.
If the test is successful, the shark should avoid the samarium-tainted meal, but not the food near the lead.
PATRICK RICE: Here she comes.
DAVID POGUE: Oh, she didn't like it at all. She was aiming right at it and she was like, "Uhhhh!"
PATRICK RICE: That was an excellent response. Notice the other fish; it doesn't have any effect on them.
DAVID POGUE: Okay, wait a minute. Now she's going for the lead.
PATRICK RICE: So there's the control.
DAVID POGUE: And she loves the lead one!
PATRICK RICE: No problem on the control, so, that's awesome.
DAVID POGUE: Since making this remarkable discovery, Patrick has experimented with designs for shark-repelling fishing hooks, and he's seen some promising results.
PATRICK RICE: The last experiment we did, we put out 46,000 hooks, and we reduced shark by-catch by 27 percent.
DAVID POGUE: Get your fresh chum, here!
This is an excerpt from the NOVA program " Hunting the Elements ."
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