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What Do Shark Researchers Do Onshore?
The initial reaction of kids, faces upturned and eyes wide open, gazing at the shark tank, most often conveys a combination of elevated energy, bravado, and anxiety. . . . In the quiet of night and trust of closing eyes to sleep, and then awakening to find that all is well, the kids’ demeanor and attitudes are often transformed into calm, awe, and respect.
—Clarinda Higgins, former assistant curator of education, the Maritime Aquarium in Norwalk, Connecticut
In sweatpants or pajamas, they nestle into cozy sleeping bags on benches padded with carpeting, in the company of their best friends. Overheard: whispers between kids, adult voices nearby, and a few snores. When they turn over and peek at their surroundings, they see rippling light and swimming forms. These are undulating fish, flapping rays, and the smooth, slow S-swim of sharks. In the room where these kids are sleeping?
The Maritime Aquarium in Norwalk, Connecticut, hosts sleep-ins in the big visitor area outside the massive glass windows of the sand tiger shark tank. Does anyone get a good night’s sleep in a slumber party with the shadowy forms and glass-eyed grins of sharks? One thing’s for sure. The kids get a fabulous opportunity to watch the animals.
The Monterey Bay Aquarium in central California is the second-largest aquarium in the world and hosts about two million visitors each year. The aquarium’s shark tank includes sevengill, leopard, spiny dogfish, and Pacific angel sharks. The shark tank is 90 feet (27 m) long and has an hourglass shape so the sharks have room to turn and glide.
Many shark species are difficult to keep in captivity. They need big tanks and lots of salt water. They sometimes become disoriented and depressed, stop eating, and die. In the wild, whale sharks swim about 33 feet (10 m) deep, covering distances of up to 21 miles (34 km) a day. In captivity, they can’t maintain this same depth and distance, so they swim in circles—hundreds of circles a day.
In the wild, whale sharks can live to be a century old. In captivity, the life span is far less. From 1980 to 1998, Japan’s Okinawa Churaumi Aquarium kept a total of sixteen sharks. They lived an average of only 502 days (a little more than a year) in captivity.
Sharks, especially large or pelagic sharks, rarely are kept in aquariums for a long time. Sharks in captivity are, however, much easier to study to learn about their swimming, sensory abilities, and sometimes reproduction. But not all scientists agree that studying sharks in captivity is the best way to understand their natural behaviors and life cycle.
And yet, sharks in aquariums do inspire young people to become scientists. Pioneering shark scientist Eugenie Clark fell in love with sharks as a child, gazing through the glass of the shark tank at the New York Aquarium. These days she might be the first to sign up for a sleepover with sharks!
Jaws in the House
As any research diver can tell you, capturing a shark and bringing it back to shore alive is not easy. Aquarists at aquariums will also tell you that it’s not easy to keep sharks in captivity. So why do we keep sharks in aquariums? And what are the benefits of having them there?
It’s true that living in captivity shortens a shark’s life span. But aquariums can successfully keep sharks for years. Researchers have learned more about shark physiology, including how female sharks reproduce without males. And aquariums raise money to pay for important shark research.
Among the biggest success stories is the sandbar shark. Its habitat is close to shore in many locations that have aquariums, so the shark doesn’t have to be transported far once it is caught. Some sharks, such as whitetip reef sharks, will hunt other fish in their tanks. But as long as aquarium divers feed them enough food, sandbar sharks won’t get hungry and become aggressive and competitive.
A Fish out of the Ocean
Before 1981 the longest any great white shark had ever been held in captivity was one day. That year SeaWorld entertainment marine park in San Diego kept a young great white for sixteen days before aquarists became concerned about its health. When the shark began having convulsions and problems with swimming, they thought it best to release it to the wild. The animal was caught by a fisher only days later.
From 2004 to 2013, Monterey Bay Aquarium in California was the only public aquarium in the world to display great white sharks. The aquarium had six of them, one after another—in the massive 1.2 million-gallon (4.5 million L) Open Sea exhibit. The first, a female, stayed 198 days before she attacked two smaller sharks in the exhibit. After that, aquarists released her back to sea. None of the others stayed very long. One major problem: they wouldn’t eat. None of the sharks died in captivity, but aquarists decided to let them go before they got too thin and weak. In 2013 the aquarium announced it would quit trying to keep great whites in captivity. It wasn’t a great life for the sharks, and visitors don’t seem to care if the aquarium has great white sharks or not. They love the aquarium no matter what.
Great whites fail in captivity. They become depressed or disoriented to the point of crashing into aquarium walls because their nature is to range widely. They swim far to stalk their prey, and they move continually to keep water flowing through their gills. Aquarium tanks just aren’t big enough. What’s more, their favorite menu item is live prey that they themselves pursue and catch. They generally turn up their noses at aquarium food. And even when great whites are returned to the sea, some will die from the stress of the change in environment.
Record-Size Fish, Record-Size Aquariums
The Georgia Aquarium in Atlanta is the world’s largest. And it holds the biggest captive shark—and the world’s largest fish—the whale shark. It can grow to 42 feet (13 m) long, close to the size of a semitrailer. The entrance to the Ocean Voyager tank at the Georgia Aquarium in Atlanta is a tunnel with a curving acrylic ceiling looking up into the tank. It’s pretty—like being in a tropical fish tank—and multicolored and sparkly. At the end of the long tunnel, visitors enter a room with a 2,361-foot (720 m) transparent wall looking into a 6.3 million-gallon (24 million L) tank. They find a place to sit or lean, and they wait a minute. There’s a gasp. Everybody points. Kids run along the edge of the tank to keep up. With what? A deep blue-gray whale shark, speckled in white, with an entourage of remoras.
This whale shark feeds on small fish in the Arafura Sea off the western coast of the island of New Guinea. Many sharks, including the whale shark, do not thrive in captivity. They become bored and depressed. Some quickly become sick and die.
The Ocean Voyager gallery is home to four whale sharks. For a fee of more than $200, visitors can even swim in the tank with the gorgeous giants. Maintaining the aquarium’s reputation as a healthy second-home environment for massive whale sharks has had its problems, though. Ralph and Norton were the first of the aquarium’s whale sharks. A commercial fishing fleet in Taiwan had caught them as bycatch in 2005. The aquarium bought them and flew them by airplane to Atlanta. They died in early 2007 after staff treated their tank with a chemical to reduce parasites.
The death of the whale sharks—and problems raising healthy beluga whale calves born in captivity at the aquarium—has raised difficult questions. Is the strain on the individual animals and the sorrow of losing them worth what we learn about them? Scott Higley is the vice president of external affairs at the Georgia Aquarium. He says the aquarium’s goal is edutainment, education about whale sharks and the entertainment and joy of seeing their awesome gorgeousness. He feels the trade-offs are worth it.
Despite controversy, aquariums continue to keep sharks in captivity. By 2016 Churaumi Aquarium had a new pair of whale sharks—a male and a female. The aquarium curator, Keichii Sato, an expert on captive care, speculated about whether the two would mate. If they did—and if they produced a baby whale shark—it would become the first time that whale shark mating and birthing is observed, in captivity or in the wild.
Pick One from the Catalog
Researchers and aquarists get to know sharks by site. They recognize individual markings and personalities. And to organize what they know about these individual sharks, researchers have developed shark catalogs. Whale catalogs rely on the distinctive tail fluke markings of humpback whales to identify individual humpbacks. Ichthyologists rely on photographs and listings to keep track of individual sharks and their movements.
One of the biggest shark catalogs is Wildbook. In 1995 marine conservation biologist Brad Norman of Murdoch University in Perth, Australia, established Ecocean, an organization for studying whale sharks. Job number one was to find a way to tell whale sharks apart, and the key lay in the spots on their bodies.
Norman realized he could use the distinctive pattern of spots to identify individual whale sharks. He worked with information architect Jason Holmberg to develop a computer program to help match spot patterns in photographs with specific sharks. Holmberg borrowed an algorithm used by astronomers to scan the sky. Instead of stars, Ecocean uses spots. Wildbook has grown to include a collection of more than fifty thousand photographs of whale sharks, which researchers use to track where the sharks swim.
What’s more, Ecocean’s Wildbook database accepts anyone’s shark photographs. So a scuba diver or snorkeler or boater can photograph a whale shark, submit pictures, and see if they get a match. Since shark scientists can’t be everywhere, this program connects them with people all over the world—and with whale sharks tagged or untagged wherever they’re found. What if your whale shark isn’t in the catalog? Then this new, unknown individual will need a name for the catalog. You may even get to name it!
Researchers also study dead sharks caught by commercial fishing fleets. Fishers haul dead sharks to necropsy labs. There, biologists examine the dead animals for many studies, including external morphology, anatomy, diet, and reproduction. They take size measurements, note the animal’s sex, and consider the number of sharks a fleet has caught. They record the capture location, maturity stage, stomach contents, and presence of parasites and any embryos a female may be carrying. The data from fishing fleets helps scientists better understand where and how deep in the ocean certain species live and whether they live in groups related to species, sex, size, and/or age. Yes, they get similar data from tagging sharks themselves. But the more eyes in the ocean—and the more sharks observed—the better the scientific understanding of how sharks use their environments.
Shark Genes
In late 2017, the marine biology community got big news: the completion of the sequencing of a great white shark genome (a map of the shark’s genes). Other projects for fully identifying and sequencing (or mapping) shark genomes are under way, including the genes of whale sharks. Genome sequencing is a historically new development in science. DNA is the basic chemical ingredient of animal genes. Long strands of DNA on chromosomes spiral within animal cells. DNA dictates the type of organism and cells that will develop in a life-form, how its cells will grow and change, what the organism will look like, and how it will behave and function. The sequence of genes on chromosomes can take years to map out. That’s because there are so many of them—from thousands to millions to billions. The first sequenced genome in history was a super-simple virus, in 1976. Twenty years later, scientists mapped a yeast genome. In 2000 a fruit fly. In 2003 scientists with the international Human Genome Project completed the human genome, mapping nineteen thousand to twenty thousand human genes. So why is it taking so long for sharks?
The answer? The great white shark genome is 1.6 times bigger than the human genome. That’s because sharks have been on Earth for so much longer than humans have—more than four hundred million years, compared to only six million years for humans. So sharks have changed and responded to millions of years’ worth of additional challenges. That means they also have more genetic material. And among the shark’s advanced genetic capabilities is the ability to resist cancer.
How did scientists discover this? Mahmood Shivji and a team of researchers already knew that cuts and other open wounds on shark and ray skin start healing in just a few hours. This quick rate of healing is much faster than in any mammal. Shivji knew that studying the shark immune system—its network of cells, tissues, and organs for fighting disease—would provide clues about fast healing. So he began to look at shark-healing genes and found two that seem to impact healing as well as resistance to cancer. Shivji and his team hope that further study will produce techniques for curing or even preventing cancers in people.