Could Cheap Magnets Help Save Sharks?

The fishing industry accidentally kills millions of sharks every year, but researchers think they've found a seriously inexpensive solution. Learn how it could work in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
Lauren Bogabam. Here we humans in general, not us on
this podcast, but kill a hundred million sharks every year.
First starters. Some people eat sharks, so they kill them
on purpose. For that reason, However, the big shark killing
culprit is accidental by catch. By catch is the collateral

(00:24):
damage of the large scale commercial fishing industry. It works
like this. Say you're in charge of a commercial shrimping boat,
and it's outfitted with all the gear you need to
catch shrimp, including a trawling net the size of a
sports field, which sinks to the seafloor and bumps along
the bottom, picking up whatever is down there. When it's
hauled back in. Some of what's in the net is shrimp,

(00:44):
but it also contains sharks, sea turtles, seals, dolphins, raise
countless animals of all descriptions. Some of these needlessly die
before they can be thrown back overboard. Some are hauled
in to port and their bodies disposed of later. The
same goes for bated long lines and gill nets, which
entangle everything that swims into them. The result is that
as many as two billion pounds that's almost one metric

(01:07):
ton of marine life is killed and wasted by the
fishing industry every year, which puts the whole a hundred
million sharks thing into perspective. But there may be hope,
at least for the sharks. A cheap, simple fix for
a big problem like this is rarely forthcoming, but according
to a study published in a twenty eighteen issue of
the journal Fisheries Research, the answer to the shark bycatch

(01:27):
problem might be magnets. Sharks are Alasmo bronx. That is,
they belong to a group of cartilaginous fishes that also
includes raisin skates, and they have special sensory organs around
their nostrils called ampulae of Lorenzini that look like little
craters all over the sharks snout. Behind these little pores
are sacks of jelly that can sense electromagnetic fields. They

(01:48):
help sharks hunt by letting them sense the bioelectricity of
their praise heartbeat, and scientists think might also help the
migrate using the Earth's magnetic field. The research team behind
the aforementioned Setti hypothesized that incorporating magnets into fish traps
might alert Alasmo bronx to their presence and reduce overall
sharks by catch. Because bony fishes, which are often what

(02:10):
fishing outfits are looking to catch, have low sensitivity to
electromagnetic fields, they figured that even if it worked to
keep sharks steering clear of the traps, it wouldn't lower
the catch rates of desirable fish. To test their hypothesis,
the research team monitored a thousand fish traps off the
coast of Sydney, New South Wales, all of which were
baited to catch Australian snapper, a segment of the industry

(02:31):
that accidentally catches sharks about ten percent of the time.
One third of the traps were set with cheap magnets
around the entrances, worth about twenty two American dollars or
thirty dollars Australian. Another third of the traps were set
with metal bars at the entrance to provide a physical barrier,
and the last third were left alone as controls. In
a press release, co author Rees Richards of the School

(02:52):
of Environmental and Life Sciences, University of Newcastle said developing
ways to reduce by catch as a priority for many fisheries.
We found the traps with magnets had roughly thirty percent
less likelihood of catching sharks and rays compared to traps without.
In addition, those traps with magnets would catch roughly more
targeted fish, which is a rare win win for fisheries.

(03:13):
Wind winds are great, but we've got a long way
to go before we make a dent in that a
hundred million sharks per year. The magnets seem to work
well for traps, but magnets won't work on long lines.
The lines are fitted with metal hooks, so magnets would
tangle the gear. More research is needed, but as fans
of these fascinating finned creatures were glad to see one
possible solution. Today's episode was written by Jesslin Shields and

(03:39):
produced by Tyler Clang. For more on this and lots
of other not so fishy topics, visit our home planet,
how stuff Works dot com