Dear Shark Man, what’s the deal with those notches on shark tails?

Welcome to  Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

Why do sharks tend to have those little notches in their tail fin? Is it like an aerodynamic thing? If you were to fill it with more shark does something magic happen?
Sincerely,

Grateful in Georgia

Dear Grateful,

That’s a great question, and I didn’t know the answer! I reached out to an expert in the structure and function of shark fins, Dr. Brooke Flammang of the New Jersey Institute of Technology, to ask. Here’s what she told me.

“Sadly, there has not (yet) been a study focused on the fluid dynamics of the subterminal lobe (the flappy bit of tissue at the end of the tail, which moves freely because of the notch) of the shark tail. However, we can come up with a really good hypothesis about how it works!

Sharks that have the notch and the subterminal lobe are mostly in the order Carcharhiniformes (and also Squalus, which is the odd duck for everything). In Carcharhiniforms, as compared to, for example, Lamnids, the angle between the dorsal and ventral lobes is small, they have a low aspect ratio, and tails are more flexible. This suggests that Carchariniforms do not generate as much power with every tailbeat as Lamnids do.

Sharks with subterminal lobes tend to be slow-swimming, epibenthic/benthic/demersal dwellers. If you are swimming slowly in an undulatory fashion, you need to generate a considerable amount of force to maintain forward propulsion because you have less inertial benefit than when you are swimming quickly with a stiffer, more streamlined body. One way to increase force generation is to increase the momentum being added to the surrounding fluid – which is to say, you need to move more water away to push yourself forward.

The subterminal lobe adds surface area but is not stiff, lacking muscular control, and trails slightly behind the rest of the dorsal lobe during a fin beat. Because it trails behind, it extends the duration of time that fluid builds momentum before being shed from the tail (and thus generating thrust). Such passive thrust enhancement would likely only be effective at slow swimming speeds with more flexible tails, such as we see within the Carchariniformes. If you fill in the notch (and lose the flappiness of the subterminal lobe) you would decrease the efficacy of this enlarged area of flexible tissue in the tail considerably.”

Congratulations, Grateful, you’ve found a question that no one has explicitly studied, and given an expert an idea for a future project! We can only guess what would happen to  shark’s swimming behavior if this notch were filled in, and Dr. Flammang’s guess is as good as anyone’s!


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Dear Shark Man, do open ocean sharks use nursery areas?

Welcome to  Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

I know that sharks that live close to the coast sometimes use “nursery areas” when they are young. Do open ocean sharks also use nursery areas?
Sincerely,
Nosey in North Carolina 

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Dear Shark Man, can rubbing a shark’s snout cause blindness?

Welcome to  Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

Someone I follow on Instagram posted this earlier this week. In this post, she claims that a shark became blind in one eye because SCUBA divers were regularly rubbing it’s snout. Is that a thing? It doesn’t seem like a thing.

Sincerely,
Frustrated in Fort Lauderdale 

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Galeophobia, Shark Teeth, and Non-Expert Awareness Campaigns: Dear Shark Man, Volume 5

Welcome to Volume #5 of Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

What’s the history of the shark’s cultural image as a sneaky aggressive predator? Do other cultures see it differently?

Sincerely,
Imaginative in Irvine

Dear imaginative,

Much of the large-scale public fear of sharks we see today can be traced to the movie “Jaws” (read my Gizmodo article about this here). Shark conservation biologists actually use the term “the Jaws effect” in peer reviewed scientific literature. Terror of sharks resulting from that movie is fairly common even among people you wouldn’t expect; for example, both of my parents are outdoorsy and have post-graduate degrees, and yet both reported being afraid to go swimming in pools or lakes the summer after Jaws came out. Personally, I don’t think that modern shark b-movies like “SharkNado” or “Two-Headed Shark Attack” inspire the same level of public misunderstanding because they’re obviously silly, but others disagree.

Media coverage of shark bites also plays a major role. If someone gets bitten by a shark anywhere in the world, it’s headline news everywhere even if the bite isn’t severe enough to require more than a band-aid. In Australia, 38% of reported “shark attacks” didn’t even involve any injury at all. This is part of why I, along with many other shark scientists, have called on the popular press to avoid the inflammatory and inaccurate term “shark attack” in favor of a typology of other terms (shark sighting, shark encounter, shark bite, fatal shark bite).

Other cultures absolutely see sharks differently. Where I now live in western Canada, coastal First Nations have stories about a supernatural being called the Dogfish Woman. In some South Pacific cultures, sharks are seen as spirits of ancestors called aumakua (briefly referenced in Moana, see below), and there are even shark gods like Dakuwaqa.

Maui in the form of a shark, from Moana. You’re welcome.

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Vegetarian sharks, non-lethal research, and friggin’ laser beams: Dear Shark Man, Volume 4

Welcome to Volume #4 of Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

I feel more and more guilty about my own meat consumption. I wonder, are there any vegan sharks?

Sincerely,
Eager in England

Dear Eager,

There are more than 500 species of sharks, and they range widely in shape, size, habitat, and behavior. However, every single species eats animals. Many eat fish, some eat invertebrates, and few eat mammals and birds, but they all eat animals. Even the filter-feeders like whale sharks are eating zooplankton, which are (tiny) animals.

Bonnethead sharks have been documented with seagrass in their stomachs, which is likely the result of accidentally ingesting seagrass while eating crabs that live among the grass. (Sometimes I fail to pick all the lettuce off of my turkey sandwich and eat it accidentally, that doesn’t mean I’m seeking out lettuce or that lettuce is a major component of my diet). Recent work by Samantha Leigh has shown that bonnetheads may be able to partially digest this seagrass, which is pretty neat. However, that does not make them vegans, or even vegetarians.

Incidentally, a member of an influential marine conservation family whose name rhymes with Mousteau once claimed that there are more than 1,000 species of sharks and most of them are vegetarian, which is…extremely not correct.

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Shark species names and hurricane sharks: Dear Shark Man, Volume 2

Welcome to volume #2 of Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

I know how you feel about sandbar sharks (even though I’m still #teamgoblinshark), but can we agree that Ninja Lanternshark is the best common name for a shark? Also, if you had an opportunity to name a shark, what would you name it? I’d name mine Storm Shark, not because of the meteorological event, but because Storm is Aquaman’s mighty seahorse steed.

Sincerely,
La Requin in Lake Buena Vista

Dear La Requin,

Ninja Lanternshark is a pretty sweet common name. My friend Vicky Vasquez was involved in the discovery and description of that species, which also has a cool scientific name (benchleyi, named after Jaws author and eventual shark conservationist Peter Benchley). If you haven’t read the great Hakai magazine story about this species, you should.

As an ecologist and conservation biologist, I am unlikely to get the opportunity to name a shark, but that doesn’t mean I haven’t thought about this. I’d love to see shark species named after influential shark conservation advocates, particularly those who engage in science-based conservation advocacy. If a new species of cownose ray is discovered, I hope that folks will consider naming it after Shark Advocates International President and frequent Southern Fried Science guest blogger Sonja Fordham, for example. And I certainly wouldn’t turn down a species named after me, if any taxonomists are reading this, though there are certainly plenty of more deserving people.

Incidentally, I have a colleague who studies marine mammal parasites. I’ve told her that I will donate to a conservation charity or her choice if a parasite that significantly annoys (but does not kill) dolphins is named after Southern Fried Science.

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Shark protections, shark careers, and sharky grammar: Dear Shark Man, Volume 1

Welcome to volume #1 of Dear Shark Man, an advice column inspired by a ridiculous e-mail I received. You can send your questions to me via twitter (@WhySharksMatter) or e-mail (WhySharksMatter at gmail).


Dear Shark Man,

Have you seen this New Scientist article (“Sharks now protected no matter whose waters they swim in?)
Is this good news? It seems too good to be true.

Sincerely,
Skeptical in Seattle

Dear Skeptical,

You are correct to be, um, skeptical. At best, this article is an oversimplification of a very complex problem. Many shark species migrate through the territorial waters of multiple nations, which complicates any conservation and management plans for these species. The Convention on Migratory Species, which is what the New Scientist article is about, is an attempt to help. However, a CMS listing is only the first step, and it does not inherently require any legal protections. Thus far, CMS listings for sharks have not resulted in any concrete legal protections for these species. The World Wildlife Fund’s shark expert, Ian Campbell, has written a great summary of why this CMS news is not the be-all end-all solution that many seem to believe, check it out here:

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