Are Sharks Becoming Extinct?

By Philip Elmer-DeWitt

Sharks have long been regarded as terrors of the deep. The mere sight of that telltale dorsal fin cleaving the water's surface instantly sends swimmers racing for the shore (with strains of the ominous two-tone theme from Jaws pounding in their heads). But in recent years these perilous predators have become a popular American entree. Commercial shark fishing has begun to threaten several species, including the thresher, mako and hammerhead. "At this point, we're talking about a marked decline," says Charles Manire, a shark researcher at the University of Miami. "But if it doesn't stop, we're going to be talking about extinction."

With shark populations in danger off the coasts of the U.S., Japan, South Africa and Australia, marine biologists are rushing to the fishes' defense. This week hundreds of experts are meeting in Sydney for the first international conference on shark conservation. Their goal: to combat the animals' long-standing image problem and advocate protective measures.

In the U.S. the National Marine Fisheries Service (NMFS) is already completing a plan that would set federal fishing quotas for 39 shark species. It would also ban live finning -- the cruel practice of catching sharks, slicing off their fins and tossing the maimed creatures back into the ocean to die. Dried fins, which fetch up to $117 per kg ($53 per lb.) in Asian markets, are used to make shark-fin soup, a gelatinous delicacy that sells for as much as $50 a bowl in a fine Hong Kong restaurant.

Ironically, the U.S. government intentionally encouraged commercial shark fishing about 10 years ago, in part to prevent overfishing of swordfish and other species. Supermarkets and restaurants were initially so hesitant to feature the fearsome fish that they marketed it under such pseudonyms as "flake" and "steakfish." But shark has since become downright trendy. To keep pace with demand, commercial shark catches in the U.S. jumped from less than 500 tons in 1980 to 7,144 tons in 1989. Last year, however, the catch was down an estimated 20%, reflecting diminished populations.

The fishing is extraordinarily wasteful. According to the NMFS, approximately 89% of the U.S. commercial catch is discarded. Part of the problem stems from the fact that hammerheads, blues and other large species prized for their fins command relatively low prices for their meat, while those with valuable meat have low-value fins. In addition, shark meat spoils so quickly that fin hunters would rather toss it overboard than be bothered with the necessary processing and refrigeration.

Sharks are unusually vulnerable to the fishermen's assault. "Top predators are not used to mortality threats and do not respond rapidly," says Gregor Cailliet of California's Moss Landing Marine Laboratories. Sharks generally take 10 to 15 years to reach sexual maturity. Most species reproduce only once every two years, and pregnancy typically lasts a year. With infant-mortality rates exceeding 50%, it is difficult for sharks to maintain their numbers.

But convincing the public that an offshore menace is worthy of protection will not be easy. Though one is more likely to be trampled to death by an elephant or gobbled up by a crocodile, sharks do kill about 25 people a year worldwide -- usually because they have mistaken a human for a seal or some other favorite prey.

On the other hand, sharks, which evolved before the dinosaurs some 350 million years ago, are of enormous scientific interest and play a vital role in ocean ecology. Ranging from the 0.1-m (6-in.) Caribbean dwarf dog shark to the 18-m (60-ft.) whale shark -- the world's biggest fish -- they boast keen intelligence and some of the sharpest senses in the ocean. Many of the 350 species are capable of hearing a wriggling fish up to a mile away, and most can smell the merest trace of blood in the ocean. The shark's eyes work like night-vision goggles, seeing well in dark water.

Humans have found many uses for the shark, aside from putting it on the dinner table. An extract of its cartilage can serve as a temporary skin for burn victims, and shark corneas have been transplanted into human eyes. Because sharks rarely develop tumors, their immune systems are being studied for anticancer agents. In addition, by preying on sick and injured fish, sharks "help keep the ocean healthy," says Manire. Some biologists believe the rise in stingrays off the Florida panhandle may be a by-product of the shark's decline. Thus an ocean without sharks might be a safer place for humans, but it might not be a very nice place to swim.

With reporting by Andrea Dorfman/New York and Elizabeth L''Hommedieu/San Francisco