by David Shiffman
David Shiffman is a Ph.D. student at the University of Miami’s Abess Center for Ecosystem Science and Policy, where his research focuses on shark behavior, ecology, and conservation. Make him feel welcome!
Quick—think of a shark!
What did it look like? Most people are only familiar with the sharks that make the news for biting people: animals like the bull shark, tiger shark, or the great white made infamous by Jaws. SCUBA divers, fishermen, or avid watchers of Shark Week might be able to name a few more species. But did you know that there are actually more than 1,200 species of chondrichthyan (sharks and their skate, ray, and chimaera relatives)?
Sharks live in habitats as diverse as coral reefs, the Arctic, and the deep sea, and come in an impressive variety of shapes, sizes, and colors. Here are 11 of my favorite amazing sharks, a collection that showcases the incredible diversity of these animals. What’s your favorite shark? Let me know in the comments below!
1. Velvet belly lantern shark (Etmopterus spinax)
A related lantern shark, Etmopterus fusus, from Last et al. 2002
The glow of a lantern shark from below (from Claes and Mallefet 2010)
These deep sea sharks are best known for their ability to glow in the dark, an ability that they are believed to use for signaling one another during mating. A glowing belly helps them camouflage themselves, as any potential predator swimming below them will see the same levels of light that would naturally reach that depth, and not a shadow that could give away their location. There are several species of lantern shark, and each has a distinctive pattern of bioluminescent light.
2. Megamouth shark (Megachasma pelagios)
Megamouth shark, from a 1990 National Marine Fisheries Service technical report
These sharks, whose awesome scientific name means “giant mouth of the deep,” were first discovered in 1976, when a heavy anchor from a U.S. Navy vessel hit one. If the anchor had been deployed fifteen seconds earlier or later, this species wouldn’t have been discovered for another eight years, and to date fewer than 50 sightings have been confirmed worldwide. Megamouths, whale sharks, and basking sharks are the only three known large filter feeding sharks, but megamouths do it a little differently. Their large mouth and unique muscle morphology suggests that these sharks may be the only fish to engage in a behavior known as “engulfing,” best known from humpback whales.
3. Atlantic sharpnose sharks (Rhizoprionodon terraenovae)
Atlantic sharpnose pups (pictured with the author during an unfortunate beard-growing contest)
While sharks are often portrayed as huge superpredators, many are actually quite small. When they're pups, Atlantic sharpnose can easily fit into one hand (see photo). These sharks are often found close to shore along beaches and estuaries during the summer, and migrate to deeper offshore waters during the winter. My favorite thing about sharpnoses is their attitude—even though they’re tiny, they’re often caught when they try to eat bait that’s bigger than they are. Though few people have heard of them (they’re often incorrectly referred to by recreational fishermen as “baby blacktips”), they are extremely common in coastal U.S. waters.
4. Sixgill sawshark (Pilotrema warreni)
A related sawshark species, Wikimedia commons
Sixgill sawsharks are endemic (native to and not found anywhere else) to coastal waters off of Southern Africa, from about Cape Town to southern Mozambique, where they live on the seafloor. Sixgill sawsharks got their clever name from the fact that they have six gill slits, atypical for sharks which normally have five. Oh, I suppose the other part of their name also comes from the GIANT SAW STICKING OUT OF THEIR FACE. Like the sawfishes, sawsharks have an elongated rostrum (snout) covered with sawlike teeth, which they use to stun and impale fishes by swinging it rapidly side to side. Additionally, a pair of sensitive barbels (fleshy whiskers) is also found on the rostrum of sawsharks, which helps them locate buried prey.
5. Goblin shark (Mitsukurina owstoni)
Goblin shark, Wikimedia commons
In addition to the unique shape of its head and its round fins, these sharks are noteworthy because of their coloration. Goblin sharks can be bubblegum pink, making them simultaneously one of the ugliest shark species and one of the cutest. They are typically considered to be solitary animals, though a large group of juvenile males was caught off the coast of Taiwan following an undersea earthquake in 2003. They usually live in the deep sea, but at least one has been documented swimming in shallow waters near Japan.
6. Greenland shark (Somniosus microcephalus)
Greenland shark, From MacNeil et al. 2012
The Greenland shark, also known as the Sleeper shark because of its relatively sluggish swimming behavior, inhabits the cold waters of the Arctic. Greenland sharks are the largest fish in the Arctic, with the biggest reported individual measuring in at over 23 feet in length. Long believed to be scavengers, Greenland sharks may actually be the Arctic’s top predator, as new evidence suggests that they can catch and eat seals, reindeer, and even polar bears! These sharks are also known for a peculiar parasite that is often found dangling from their eye, which is responsible for the single weirdest question I ever got during one of my public education talks (someone asked how the sharks train the parasites to sit in their eye socket.)
The Trouble With Sharks These species of sharks are unique and fascinating, but sharks as a group are in deep trouble. According to the IUCN Shark Specialist Group, 17% of all known chondrichthyan species (and 1/3 of all open ocean chondrichthyan species) are Vulnerable, Endangered, or Critically Endangered. Scientists have reported population declines in some shark species of 90% or more in the last few decades in areas where sharks used to be abundant. To learn more about the threats facing sharks and how you can help, please follow @WhySharksMatter on Twitter.
7. Cookie-cutter shark (Isistius brasiliensis)
Cookie cutter shark, Wikimedia commons
Cookie-cutters have a bizarre feeding behavior known as “ecto-parasitic predation” that’s unique among shark species. Basically, this means that they take relatively small circular bites out of the sides of their prey rather than consuming it. These bites have been documented in swordfish, tuna, whales and dolphins, the outer rubber-like hulls of submarines, and, in one case, a human. The only person who has been bitten was in the process of swimming across a deep ocean trench between two islands, at night, while being lit from above by powerful searchlights mounted on a boat.
People often ask me what they can do to reduce the chances of being bitten by a shark, so there you have it—don’t do that.
8. Common thresher shark (Alopias vulpinus)
Common thresher shark, Wikimedia commons
Thresher sharks are known for the extremely long upper lobe of their caudal fins, which can be almost as long as the rest of the animal. These tails are used to stun schools of small bait fish like anchovies or sardines, which make up the majority of the diet of threshers. Thresher sharks are also noteworthy from a physiological perspective because of the presence of an endothermic organ that helps keep their brains and eyes warmer than the surrounding cold waters in which they live. I suspect that, like most other highly evolved creatures, thresher sharks keep the rest of their body warm through the use of a Snuggie.
9. Pacific angel shark, (Squatina californica)
Pacific angel shark, Wikimedia commons
Angel sharks are some of the only ambush predators in the shark world. Rather than actively chasing their prey, these flattened sharks lie in wait partially buried under the sediment and strike when something swims close enough to their mouth. Some angel sharks have been documented waiting in the same spot for several days until food comes along, a behavior I have been known to engage in from time to time. These sharks are one of the few species targeted for their meat, and were at one point the most commonly caught shark in California.
10. Spotted wobbegong, (Orectolobus maculatus)
Wobbegong, Wikimedia commons
In addition to having a delightful name (which means “beard” in the language of Aboriginal Australians), wobbegongs are bottom-dwellers which often rest under coral ledges or rocks during the day. These sharks are sometimes sold as “fish and chips” in their native Australia, and they are also sometimes killed for their uniquely colored skin (which is made into leather). Wobbegongs are noteworthy for being one of the few species of sharks which have been observed being eaten by seals.
11. Spinner shark (Carcharhinus brevipinna)
Spinner shark, UN FAO
These sharks are named for their incredible acrobatic feats—they often jump out of the water while (you guessed it) spinning. This behavior is the end result of swimming towards schools of prey from below at high speeds. The easiest way to tell a spinner shark from the similar-looking blacktip shark is by counting the number of fins which have black tips on them. Believe it or not, spinner sharks have one more fin with black tips than blacktips do—the anal fin.
David Shiffman is a Ph.D. student at the University of Miami’s Abess Center for Ecosystem Science and Policy, where his research focuses on shark behavior, ecology, and conservation. When he isn’t in the field, where he has interacted with more than 2,500 sharks to date, David is actively involved in educating the public about these incredible and misunderstood predators. He writes about sharks for SouthernFriedScience.com, talks about shark conservation on Twitter (@WhySharksMatter), and gives public education presentations to schools and community groups. Additionally, the lab where David works, the RJ Dunlap Marine Conservation program (RJD.Miami.edu), has taken thousands of high school students into the field to learn about sharks and participate in their long-term shark research projects. If you and your company, school group, or club are interested in joining them for a shark tagging trip, let him know! He’s also happy to answer any questions that you have about sharks.