Science & Technology

5 Harmful Myths About Sharks

Shark Week is here! *Cue the music.* And we're here to hit you with a dose of shark facts so you can impress all of your friends all week long.

1. Sharks can smell a drop of blood in the water.

Lots of people think sharks can smell blood from miles away, and that makes some swimmers think they shouldn't go in the water if they have a papercut. In 2010, Dr. Tricia Meredith, an assistant research professor at Florida Atlantic University, wondered if that could really be true. So, she did some research. Dr. Meredith took sharks from their habitats and tested their sense of smell using amino acids and blood-like substances.

In the end, Dr. Meredith found that the sharks couldn't smell any better than a salmon could. "We like to paint them as very special," said Dr. Meredith in an interview with the podcast Science Vs., "but, y'know, they're just fish." Sharks do still have bigger teeth than salmon, of course, so they're still worth watching out for.

2. Sharks don't get cancer.

Even though there's a book called "Sharks Don't Get Cancer," they totally do. The 1992 book by I. William Lane and Linda Cormac not only claimed that sharks rarely get cancer but also suggested that ingesting shark cartilage could actually fight cancer. But — spoiler alert — it can't. For more than 150 years, scientists have known that sharks can get cancer. Sadly, this is no harmless myth, according to a 2004 study published in Cancer Research. For one, shark populations are declining as the animals are hunted for their supposedly cancer-curing cartilage. Also, some cancer patients seem to pass up effective treatment in favor of shark cartilage. So this is an important one to debunk: Sharks get cancer, and their cartilage doesn't cure it.

Tiger shark at Tigerbeach, Bahamas.

3. Sharks hunt humans.

Look. Shark attacks are super, super rare. According to the International Shark Attack File at the Florida Museum of Natural History, over the past decade, only 77 attacks occurred each year on average, and less than 10 percent of those were fatal — and that's worldwide. Your chances of being attacked by a shark while in the water are 1 in 3.7 million — drastically lower than your 1 in 1,134 chance of simply drowning. Heck, 100 times more people die annually from skin cancer than they do from shark attacks.

It's true that recorded attacks are on the rise since the 1960s. But that's just because people are swimming in the ocean more often, and scientists are better at gathering data now. Sharks don't actually seem to be getting more hostile toward humans.

4. If sharks stop swimming, they die.

Most sharks can breathe in two different ways, known as buccal pumping and ram ventilation. When they breathe with buccal pumping, muscles in their cheeks pull water into their mouths and out over their gills. With that method, some sharks can lie motionless on the seafloor. Ram ventilation, however, employs constant swimming to keep water moving over the gills. It's this second breathing method that makes people think sharks have to keep swimming to get oxygen, but actually, only about two dozen species use ram ventilation alone — and it's true that these species, including the great white shark and the whale shark, would have trouble breathing if they couldn't swim. However, almost all other species of shark use either buccal pumping or both methods.

5. Sharks have no predators.

This one's a bummer. It might be tempting to think that with all their big teeth and swimming power, sharks are the predator-less kings of the ocean. But according to the World Wildlife Fund, humans actually kill about 100 million sharks per year, usually for food, sport, or as accidental catches with other fish. In 2012, scientists from Stony Brook University and the Chicago Field Museum even found that some shark-fin soup served in the United States contained fins from endangered species like scalloped hammerheads, smooth hammerheads, school sharks, and spiny dogfish.

Liz Karan, a Pew Environment Group scientist, told the Washington Post, "The soup test is significant because it shows the United States is also contributing to the global decline of sharks. And Americans who eat the shark's fin soup may be consuming an endangered species without even knowing it." Yikes.

To combat climate change and overfishing, the World Wildlife Fund says we should keep sharks in mind: "With our oceans severely degraded, restoring sharks is key to improving the resilience of these water bodies to climate change." So, if you're looking for something to snack on to celebrate Shark Week, don't choose shark-fin soup (or shark-cartilage supplements, for that matter!). Watch "Jaws," perhaps. Eat goldfish crackers. Or just share the truth about sharks with someone you love.

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Get a glimpse of some jaw-some images in the photography book "Michael Muller. Sharks." We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Kelsey Donk July 29, 2019

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