Maws

With their huge gaping mouths and enormous bodies, basking sharks look a lot more fearsome than they act

• Michael Tennesen
• Dec 01, 1993

The sight could send shivers down a novice deep-sea diver's spine: a 20-foot shark. mouth wide open, crusing through the sea only a few yards away. But in Pacific waters off Santa Barbara. California, photographer Howard Hall held his ground and captured on film the beast. An experienced diver, Hall knew the creature was a basking shark, a species, he says, that seems "totally uninterested in humans."

Growing up to 45 feet in length and 6 tons in weight. the basking shark is the second largest fish in the world. It is a seemingly gentle giant. feeding only on plankton. It also is an enigma-a species that for decades was ignored by scientists, despite its occurrence in heavily traveled coastal waters. "Only in recent years have we begun to study basking sharks and attempt to understand their behavior." says Bob Lea. a marine biologist with the California Department of Fish and Game.

The basking shark's size makes it a freak among sharks. Half of the world's roughly 570 shark species are less than 3 feet long. Only 14 species exceed 12 feet and three of these feed on plankton. (The largest species, the whale shark. grows as long as 60 feet.)

Basking sharks roam most of the world's cool and temperate seas. but experts know little about their population levels. Even the sharks' occurrence in U.S. waters is a riddle. "Why they appear and disappear is a mystery" says Lea. The huge creatures apparently range along the Pacific Coast of the United States only in winter and along the Atlantic Coast only in summer.

The basking shark's foraging habits are less mysterious to scientists. The creature feeds by swimming slowly-about 2 knots-through plankton blooms at the ocean's surface. its mouth agape, its back exposed in the "basking" behavior that earned the animal its common name. Water enters the creature's mouth, then exits through gill slits that look like nooses looped around the shark's neck. Each gill is fringed with about 1,000 plankton-trapping rakers. which resemble the tines on a comb but are as long as 6 inches. "It's been estimated that a basking shark can filter as much as 2,000 gallons of water an hour," says fisheries-industry biologist Ralph Owen. who studied the species as a graduate student at the University of Rhode Island.

Fishermen from many countries have long pursued basking sharks for their oil-rich livers. And like many shark species, basking sharks are vulnerable to overfishing. "They don't become sexually productive until late in life, and they probably don't produce a lot of young," says Lea. "It's easy to rapidly reduce the population."

The fortunes of basking sharks that range in Atlantic waters off the United States improved markedly last spring. after the National Marine Fisheries Service approved new shark-fishing regulations. The rules, which protect baskers and 38 other shark species, mandate harvest limits, increase federal monitoring and ban shark fishing by foreign vessels. Similar regulations for U.S. Pacific waters, Where this gentle giant was photographed, have not yet been implemented.