Under Attack
Forget ‘Jaws’. It’s human, not sharks, who are
by far nature’s most feared predators.
Biologists like to blame Peter Benchley’s bestselling 1974 novel ‘Jaws’ and the Steven Spielberg movie that followed for the shark’s fearsome reputation as a mindless, relentless, consummate predator. The truth is that people have always been terrified by sharks, probably since humans first ventured into the sea. Who can blame them? As any survivor or witness well knows, a shark attack, especially by one of the larger species considered man-eaters------great whites, bull sharks, tiger sharks-------is mind-numbing in its speed, violence, gore and devastation.
What most people don’t realize is that it almost never happens. Far more people are killed by bees, poisonous snakes and elephants, as well as bathtub falls and lightning strikes. It’s much more dangerous to drive to the beach than to venture into the water once you get there.
Humans, in short, have little to fear from sharks. The reverse, however, isn’t close to being true. Fish of all kinds are being hauled from the sea faster than they can reproduce, but until quite recently sharks were exempt from this reckless harvest. Not anymore. Each year between 30 million and 100 million sharks are caught for their meat (boneless and mild-tasting), their fins (a great delicacy in Asia), their hides (source of an exotic, high quality leather), their jaws (worth thousands of dollars from collectors) and their internal body parts (made into everything from lubricants to cosmetics to ‘health’ products of dubious value).
And at least one shark is accidentally killed, usually by long lines set by shrimp and tuna boats, for every one that is caught deliberately, according to the United Nation’s food and Agriculture Organization. When you add it all up, each human who dies in the jaws of a shark is avenged roughly 6 million-fold.
Largely as a result of this relentless slaughter, the populations of some shark species have plummeted an estimated 80% over the past decade. “At the current rate,” predicts marine biologist Merry Camhi of the National Audubon Society’s Living Oceans Program, “some species will reach ecological extinction within 10 years”
But why should anyone care? In fact, there are plenty of reasons, starting with the creature’s pure elegance of design. Sharks first appeared on Earth 400 million years ago, and after about 200 million years of evolutionary trial and error, nature pretty much ran out of ways to improve on its handiwork. Today more than 350 species swim the planet, ranging in size from the less-than-30-cm-long wart shark and pygmy ribbontail catfish shark to the 15-m whale shark. Sharks have insinuated themselves into every marine environment from the Arctic to the tropics. One species, the bull shark, even ventures into rivers and lakes as far as 3,200 km from the nearest salt water.
Sharks were the first creatures in evolutionary history to develop an immune system. Biomedical researchers believe that if we can figure out how theirs works, we’ll gain valuable insights into our own. A shark could someday save your life-----if the creature isn’t already extinct.
Beyond that, sharks have immense practical value. While shark cartilage does not, despite the claims, prevent cancer, it has been used to make artificial skin for burn victims. Shark corneas have been used experimentally for human transplants. Shark blood contains anti-clotting agents. Shark-liver oil seems to aid white-blood-cell production.
Sharks play a crucial role in keeping aquatic wildlife in balance. Scientists now understand that the ocean ecosystem has been evolving over hundreds of millions of years as an integrated whole—a biological machine in which each component has a vital function. For most sharks, that function is to serve as what biologists call an apex predator, the ocean equivalent of a lion or tiger or bear. Not only do they keep prey populations in check, but they also tend to eat the slowest, weakest and least wily individuals. In so doing, they improve the target species’ gene pool, leaving the smarter, stronger individuals to reproduce.
When an apex predator is removed from the food chain, this carefully balanced machine tends to go haywire. Without wolves and mountain lions to keep them in check, for example, some deer populations in the US have skyrocketed. And in just the same way, experts believe, overfishing of sharks off Australia and Tasmania years ago led to an explosion in the octopus population.
Today biomedical scientists are on the trail of deeper mysteries. For some reason, sharks rarely get tumors-----a surprising fact that could lead to new cancer treatment. Known carcinogens injected into sharks don’t trigger malignancies; they don’t even cause the sorts of genetic damage that leads to tumors in other animals.
No one knows why. Their resistance to cancer, however, has nothing to do with their cartilage, despite the extravagant claims by people who peddle shark-cartilage pills. Assertions that it does are based on a tiny grain of scientific truth. Shark cartilage---and cow cartilage, for that matter---does contain minute quantities of a compound that inhibits blood-vessel growth, and tumors depend on the rapid growth of internal blood vessels that can feed them.
Nevertheless, shark cartilage is hot, and sharks are being slaughtered wholesale to produce it; a single processing plant in Costa Rica reportedly turns 235,000 sharks into cartilage pills every month.
Sharks are also taken by the millions for their fins----a practice that scientists and conservationists find especially disturbing. Often, the fins are hacked off and the sharks are thrown back into the water, alive but mortally wounded, to bleed to death. It isn’t as though the fins are being fed to starving children. They are used in Asia for shark-fin soup, a delicacy that fetches up to $150 a bowl.
Though far less profitable, shark meat has also enjoyed a sales boom since the early 1980s. Tuna and swordfish stocks began to dwindle at that time, and the US government encouraged fishermen to pursue other targets. That may have been a big mistake. Traditional food fish, like cod and tuna, grow quickly and lay millions of eggs at a time. Sharks, by contrast, can take two decades to reach sexual maturity, have a long gestation period and bear only a few young at one time. Killing a relatively small number of females can dramatically limit the reproductive potential of an entire species.