I have spent much of the last 30 years underwater. I have explored the deep on thousands of scuba dives and numerous submersible trips to 18,000 feet (5,500 meters) below the surface. Yet during all these journeys, I have only rarely encountered some of the ocean's biggest mysteries: deep-sea sharks.
Twenty-seven years ago, a small cable outfit broadcast a week of television all about sharks. In the many years since, while the Discovery Channel's Shark Week has not shied away from controversial shows depicting attacks, it has also brought sharks into the public consciousness and educated the public about their importance to our oceans.
The casual fan of Shark Week can probably name the big three: the great white, tiger and bull sharks. They are the DiCaprio, Clooney and Pitt of the shark world. As important as these are, they are just three members of the shark family, which includes over 400 species. To me, the most amazing sharks are the little-known species that lurk in the deep sea.
Over the years, we've learned quite a bit about shallow-water sharks because they're in the reef -- in the dive zone where we can see them. Deep-sea sharks seem almost alien to us because they're so deep in the ocean that it's hard to get there and observe them. The pressure is extremely high, temperatures are extremely low and only in the last several decades have we had underwater vehicles, robots and submarines that can get down into these depths.
Here are some of the few things that we do know about them:
- Goblin shark: One of the strangest-looking fish in the ocean, very few specimens have been caught and studied. It was first found in Japan, but is probably widely distributed in the deep sea.
- Frill shark: This true example of a living fossil is typically never found in shallow water; when it is, it's usually in distress. Eel-like in shape, and up to 6 feet (1.8 meters) long, they can distend their mouths open and eat things that are more than half their body length.
- Bluntnose sixgill shark: This shark can grow up to 16 feet (5 meters) long and 1,300 pounds and can attack like a great white shark, but with a stronger bite. Though primarily a deep-sea species, some make trips to the shallows at night, allowing for the unsuspecting night-diver to chance upon them.
- Greenland shark: This is one of the largest sharks in the world, reaching up to 24 feet (7.3 meters) in length. It is probably the most northern-ranging of shark species, living mainly in deep, very cold water of the high North Atlantic and Arctic Oceans The species has been found at a depth of more than 7,000 feet (2,130 meters), yet stomachs of some specimens have contained polar bear, pieces of horse and even an entire reindeer. Whether those animals were eaten at the surface or scavenged from the bottom is not known.
- Megamouth shark: This species was only first discovered in the ocean in 1976; with only about 50 sightings worldwide, it remains one of the poorly known sharks. This species filters plankton from the water, a feeding mode that it may have evolved independently from the two other known filter-feeding sharks, the basking shark and whale shark.
We know that all sharks are important to human well-being. Some evidence of this is well-proven; other potential benefits remain unstudied. We know that sharks keep the food web in check and are a vital part of healthy fisheries. They boost local economies through ecotourism, have the potential to cure a variety of diseases, are a vital part of the carbon cycle and inspire smart design in items ranging from swimsuits to mechanisms that harness wave energy.
Studying deep-sea sharks in particular could bring us valuable knowledge. Science is on the cusp of understanding the power of genomes in nature. These deep-sea sharks, along with other specialized deep-sea organisms, including bacteria and worms that live on the seafloor, contain an infinite encyclopedia of genetic knowledge that has allowed them to survive in the most extreme environment on our planet. Their evolutionary secrets could open doors to understanding our own existence and survival on Earth.
One thing we do know is that sharks in all parts of the ocean are under pressure from human activity. Overfishing and unsustainable practices, like shark finning, account for the death of an estimated 100 million sharks per year. Even these deep-water dwellers face these threats.
The oceans' depths are no doubt hiding many more secrets that human beings have yet to lay eyes upon. The Megalodon -- an extinct shark the size of a school bus -- may be gone, but there is still a whole range of deep-sea sharks in our oceans waiting to be studied, with probably others waiting to be discovered. As long as we can give them the same attention and protection we give to great white, tiger and bull sharks, I know there is much we can learn from them about how our oceans work.
This originally appeared on Conservation International's Human Nature Blog.
Greg Stone is the executive vice president for Conservation Internationals's Betty and Gordon Moore Center for Science and Oceans. He will be featured this evening on Discovery Channel's Shark Week at 10 p.m.EST on the show "Alien Sharks of the Deep" and will be a guest live in studio for "Shark After Dark" at 11 p.m. EST.
Follow Greg Stone on Twitter: www.twitter.com/GregStoneCI