Every jittery Vineyard beachgoer is familiar with the iconic image of the restless great white patrolling the shallows, mouth agape, in search of a fleshy excuse to close it. Stacks of shark books celebrating the more lurid aspects of their behavior, particularly their extremely rare propensity to attack humans, already fill library shelves, but in Demon Fish, Washington Post environmental reporter Juliet Eilperin makes the case that the more fearsome animal is in the mirror. Humans are emptying the seas of sharks at an astounding rate, just as we are beginning to learn the basics of the world they inhabit. It is a world that is almost humbling in its separateness from humankind but whose fate is tied inextricably to it.

“Sharks are dangerous but so are we,” said Ms. Eilperin in a telephone conversation last week.

Our fear of sharks is elemental and understandable, and Western civilization has long regarded the animal with something approaching an atavistic revulsion. But in her far-flung reporting for the book, Ms. Eilperin encounters indigenous communities, such as the shark-callers of Papua New Guinea, where sharks command a reverence not reserved for any other animal. And even there centuries of a communal, respectful co-existence with the sharks, which are thought to augur good fortune or act as a medium with ancestors, are giving way to economic pressures that make the commercial, decimating harvest of shark fins more attractive.

This demand for fins is driven by one dish: shark’s fin soup. To understand the phenomenon Ms. Eilperin met with shark fin traders in Hong Kong, some of whom who offered halfhearted (and ultimately empty) professions of concern about the endangered animals, and even ordered a bowl for herself. She was less than impressed with the delicacy which is a staple of wedding banquets and corporate power lunches in China.

“I was amazed when I actually had a bowl of shark’s fin soup in Hong Kong, both by the fact that there was just a tiny, tiny amount of [shark fin] noodles in there and the fact that they were flavorless,” she said. “It’s all about status and nothing about culinary reward. That really does seem pretty ironic that this is something you could have missing from the soup and no one would notice.”

Conspicuous consumption, and the attendant ego-fueling sense of conquest over such a formidable animal is driving sharks to the brink. Elsewhere they face similar threats from humans seeking validation through their capture, whether from testosterone and beer-soaked stag party fishing charters in Florida or from the unscrupulous owners of private aquariums. An estimated 70 million sharks are killed every year, and as with most modern ecological fables, the story can be terribly depressing.

Still Ms. Eilperin is at least guardedly optimistic about the fate of an animal that has already survived almost a half-billion years on planet earth. Public opinion among younger generations of Chinese may be turning against the exploitation of the sharks for a largely flavorless luxury dish, and Ms. Eilperin sees progress amid the slow-footed regulatory bodies charged with protecting them.

“We’re seeing tons of activity in the United States,” she said. “On the West Coast, Hawaii was the first state to ban the sale and trade of shark fins and Washington and Oregon followed this summer. California is in the midst of a debate of a shark fin ban that could become final in a matter of weeks.”

Last year President Obama signed into law a bill that requires fishermen to land sharks in U.S. waters with their fins attached.

Other newer industries also hold promise for the protection of the animals. Ms. Eilperin documents the rise in eco-tourism ventures in the Gulf of Mexico that center around the lumbering, polka-dotted whale shark, the largest fish in the world.

“I think eco-tourism is part of the answer and I think it serves two important purposes,” she said. “One is it provides an economic driver for change in some developing countries.”

Ms. Eilperin points to new studies that indicate that a single shark can be worth at least $2 million over the course of its lifetime, given the diving and snorkeling tourism revenue it generates.

“For poor countries that are trying to decide whether to fish sharks or to conserve them that could really prompt a shift,” she said. “I also think on a broader level shark tourism can help change peoples attitudes about them. It’s rare for someone to actually go on a cage-diving adventure or snorkeling experience where they’re seeking out sharks and not come away with some reverence for these animals.”

In her own experience diving with the animals, having dedicated so much of her time to their study, she was always amused by how uninterested they were in her.

“The thing that I was most struck by when I went in the water with sharks is how indifferent they were to me being in the water,” she said. “In a way that was pretty comforting because if they’re not focused on me it means they’re not going to strike me but more importantly it made me recognize that they just exist in this separate universe. I’m actually not part of their world.”