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 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, 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 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 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 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 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 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 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. 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 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