WEBVTT - Could Cheap Magnets Help Save Sharks?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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<v Speaker 1>Lauren Bogabam. Here we humans in general, not us on

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<v Speaker 1>this podcast, but kill a hundred million sharks every year.

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<v Speaker 1>First starters. Some people eat sharks, so they kill them

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<v Speaker 1>on purpose. For that reason, However, the big shark killing

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<v Speaker 1>culprit is accidental by catch. By catch is the collateral

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<v Speaker 1>damage of the large scale commercial fishing industry. It works

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<v Speaker 1>like this. Say you're in charge of a commercial shrimping boat,

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<v Speaker 1>and it's outfitted with all the gear you need to

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<v Speaker 1>catch shrimp, including a trawling net the size of a

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<v Speaker 1>sports field, which sinks to the seafloor and bumps along

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<v Speaker 1>the bottom, picking up whatever is down there. When it's

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<v Speaker 1>hauled back in. Some of what's in the net is shrimp,

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<v Speaker 1>but it also contains sharks, sea turtles, seals, dolphins, raise

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<v Speaker 1>countless animals of all descriptions. Some of these needlessly die

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<v Speaker 1>before they can be thrown back overboard. Some are hauled

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<v Speaker 1>in to port and their bodies disposed of later. The

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<v Speaker 1>same goes for bated long lines and gill nets, which

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<v Speaker 1>entangle everything that swims into them. The result is that

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<v Speaker 1>as many as two billion pounds that's almost one metric

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<v Speaker 1>ton of marine life is killed and wasted by the

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<v Speaker 1>fishing industry every year, which puts the whole a hundred

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<v Speaker 1>million sharks thing into perspective. But there may be hope,

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<v Speaker 1>at least for the sharks. A cheap, simple fix for

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<v Speaker 1>a big problem like this is rarely forthcoming, but according

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<v Speaker 1>to a study published in a twenty eighteen issue of

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<v Speaker 1>the journal Fisheries Research, the answer to the shark bycatch

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<v Speaker 1>problem might be magnets. Sharks are Alasmo bronx. That is,

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<v Speaker 1>they belong to a group of cartilaginous fishes that also

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<v Speaker 1>includes raisin skates, and they have special sensory organs around

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<v Speaker 1>their nostrils called ampulae of Lorenzini that look like little

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<v Speaker 1>craters all over the sharks snout. Behind these little pores

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<v Speaker 1>are sacks of jelly that can sense electromagnetic fields. They

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<v Speaker 1>help sharks hunt by letting them sense the bioelectricity of

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<v Speaker 1>their praise heartbeat, and scientists think might also help the

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<v Speaker 1>migrate using the Earth's magnetic field. The research team behind

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<v Speaker 1>the aforementioned Setti hypothesized that incorporating magnets into fish traps

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<v Speaker 1>might alert Alasmo bronx to their presence and reduce overall

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<v Speaker 1>sharks by catch. Because bony fishes, which are often what

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<v Speaker 1>fishing outfits are looking to catch, have low sensitivity to

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<v Speaker 1>electromagnetic fields, they figured that even if it worked to

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<v Speaker 1>keep sharks steering clear of the traps, it wouldn't lower

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<v Speaker 1>the catch rates of desirable fish. To test their hypothesis,

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<v Speaker 1>the research team monitored a thousand fish traps off the

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<v Speaker 1>coast of Sydney, New South Wales, all of which were

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<v Speaker 1>baited to catch Australian snapper, a segment of the industry

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<v Speaker 1>that accidentally catches sharks about ten percent of the time.

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<v Speaker 1>One third of the traps were set with cheap magnets

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<v Speaker 1>around the entrances, worth about twenty two American dollars or

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<v Speaker 1>thirty dollars Australian. Another third of the traps were set

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<v Speaker 1>with metal bars at the entrance to provide a physical barrier,

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<v Speaker 1>and the last third were left alone as controls. In

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<v Speaker 1>a press release, co author Rees Richards of the School

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<v Speaker 1>of Environmental and Life Sciences, University of Newcastle said developing

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<v Speaker 1>ways to reduce by catch as a priority for many fisheries.

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<v Speaker 1>We found the traps with magnets had roughly thirty percent

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<v Speaker 1>less likelihood of catching sharks and rays compared to traps without.

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<v Speaker 1>In addition, those traps with magnets would catch roughly more

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<v Speaker 1>targeted fish, which is a rare win win for fisheries.

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<v Speaker 1>Wind winds are great, but we've got a long way

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<v Speaker 1>to go before we make a dent in that a

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<v Speaker 1>hundred million sharks per year. The magnets seem to work

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<v Speaker 1>well for traps, but magnets won't work on long lines.

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<v Speaker 1>The lines are fitted with metal hooks, so magnets would

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<v Speaker 1>tangle the gear. More research is needed, but as fans

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<v Speaker 1>of these fascinating finned creatures were glad to see one

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<v Speaker 1>possible solution. Today's episode was written by Jesslin Shields and

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<v Speaker 1>produced by Tyler Clang. For more on this and lots

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<v Speaker 1>of other not so fishy topics, visit our home planet,

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<v Speaker 1>how stuff Works dot com