Love The Shark
June 19, 2008 - Forbes - NY
By Elisabeth Eaves
Shark hysteria came early to the Northern hemisphere this year. Markus Groh, a 49-year-old Austrian attorney, died in February after a shark bit him in the Bahamas. "Shark Horror," ran the headline in a British tabloid. "They are filling the waters off of Florida," announced an NBC news anchor.
Only a few of the hundreds of news reports added that in all of 2007, there was only one shark-attack fatality worldwide. In the last six years globally, sharks have bitten humans at a rate of 63 times a year, of which only 3.8 incidents a year were fatal, says George Burgess, who runs the International Shark Attack File. Shark attacks have increased decade on decade for the last century--but only because as the human population grows, more and more people go into the water. "It's an odds situation," Burgess says. Of some 500 shark species known to humans, only between 10 and 15 have been implicated in biting people.
The real shark tale is that the marine predators have vastly more to fear from people than people do from them--and that we are recklessly destroying them at our peril. "Sharks are swimming around with answers to problems, even problems in human health," says Robert Hueter, director of the Mote Marine Laboratory's Center for Shark Research. Their physiology is still little understood compared with other animal groups, and their unusual immune system may hold a key to fighting cancer.
Shark populations are falling worldwide, with conservative estimates claiming tens of millions killed every year. Forty-four separate species of sharks and skates--among sharks' closest evolutionary relative--are either endangered or critically endangered. Studies of different shark species, in different regions and over different time periods report everything between a 10% and 99% decline in shark populations. "There's no study that shows that sharks have increased," Hueter says.
Many governments have tried to limit or even ban shark fishing. But they are up against soaring demand, particularly for shark fins. With rising wealth in China and other parts of Asia, more shark fin soup than ever is being consumed. Fins are usually worth more on the market than all the meat on the rest of the animal--hence the practice of fining, banned by the U.S., in which the fisherman cuts off the fin and throws the rest of the animal in the water to die.
Right now biomedical research on sharks is furthering our understanding of human illness. Fishermen had always believed that sharks had low rates of disease, because they never caught sick ones. When, in the '60s, the Smithsonian started keeping track of neoplasia--new tissue growth, including tumors--in fish, the sailors' lore was corroborated. Fewer than 15 malignant tumors have ever been documented in sharks, skates and rays (another close relative) compared with many thousands in bony fish, according to Carl Luer, the program manager for biomedical research at Florida's Mote Marine Laboratory.
Thirty years ago, Luer set out to explore this low rate of disease. He spent 10 years using carcinogens to try to induce cancer in sharks and skates, to no avail. Then he and a colleague, Cathy Walsh, turned their attention to trying to understand shark immunology. They were able to confirm that sharks have a unique lymphoid tissue, not present in any other animals, that does nothing but make immune cells. Eventually Luer and Walsh found that the unusual immune cells could, in the lab, secrete a substance that inhibits human tumor cells. So far they've tested the substance--they're still not exactly sure what it is--on 18 different human tumor cell lines, including breast and pancreatic cancer. It's inhibited all of them.
Now Luer, who has obtained two patents for his lab's methods, is seeking more funding to move forward. He hopes to someday be able to understand and identify sharks' tumor-inhibiting secretion, making it possible for scientists to synthesize it.
But biomedical research is just one reason to love sharks.
To be sure, many marine species are under threat these days, due to overfishing and pollution, and scientifically speaking, one species isn't more valuable to an ecosystem than another. But as a so-called "top predator" (meaning they are at the top of the food chain), the precipitous decline of shark populations deserves special attention. "They really are an indicator species for what we're doing to the sea," says Burgess. "If an animal that's that well-designed could start tumbling in terms of its population numbers around the world, what's that telling us about the things below it in the food chain?"
That "design" is so hearty that sharks as a group have survived for 400 million years, predating dinosaurs. Their olfactory senses are extremely sharp, even surpassing the exceptional acuteness possessed by dogs. Sharks can sense the electromagnetic fields that are put off by all animals, and detect small changes in the pressure in the water. Scientists in Florida think that sensitivity to water pressure is the reason 13 young blacktip sharks, much to the scientists' surprise, fled their coastal nursery habitat just before a tropical storm battered the area, returning after it had subsided.
Ecosystems being complicated, it's tough to predict the effects of a shark population collapse. But in 2005, scientists Jordi Bascompte, Carlos Melián and Enric Sala published a study in the Proceedings of the National Academy of Sciences showing that shark overfishing in the Caribbean had degraded the whole ecosystem. Shark numbers fell, so the number of groupers, on which they prey, rose. Groupers normally prey on parrotfishes, so with more groupers around, the parrotfish population fell. Parrotfishes eat the algae that grows on coral reefs. With fewer parrotfish in the area, the coral reefs became covered in algae, which blocks the sunlight coral needs to survive. "When the reefs die, the whole system dies," Hueter says.
Sharks have also come to play an important economic role in many societies. "Just wiping these animals off the face of the earth could be one of our greater mistakes in resource utilization," Hueter says. Shark meat, which can be harvested in a sustainable fashion, has become a major source of protein in some developing nations. Sharks are a valuable fish in aquariums and in ecotourism, with hundreds of small companies worldwide taking paying customers on shark-watching tours. The WWF determined that tourism in 2005 to a single site in the Philippines to see whale sharks--the world's largest fish--brought the country $623,000. The same year, a single Australian whale shark site, Ningaloo Reef, generated $7.8 million over two months. Fishermen also stand to lose their livelihood if sharks go.
Meanwhile, shark populations worldwide continue to shrink, taking their secrets with them. So the next time the headlines scream "shark attack," spare a thought for the poor shark.