Wednesday, December 17, 2008

Scientific American Earth 3.0-Isla Guadalupe

A windless dawn rises over Isla Guadalupe, 150 miles west of the Baja California coast. Rolling slightly in a gentle Pacific swell, our 80-foot trawler Horizon motors toward the island’s north end. The skipper, Greg Grivetto, is standing the final watch of a 20-hour passage from San Diego. He glances down through the bridge windows at the dozen or so passengers gathered on Horizon’s foredeck. We’re shaking off sleep, gabbing, sipping coffee, eager to catch sight of our first landfall on this remote volcanic rock. In the distance, sunlight outlines the arc of Guadalupe’s northeast inlet. There, deep in flat, dark water, something is also stirring, and everyone onboard is thinking about it.

The inshore waters of Guadalupe make up one of the few known habitats for this formidable migrating creature. It is the world’s largest predatory fish, typically 13 to 16 feet long, weighing 1,500 to 2,500 pounds. The great white is the undisputed king of the cartilage-skeletoned vertebrates that have been swimming through the seas for 400 million years and the supreme iteration of an “apex predator”—top dog—in its watery world. To scientists and shark devotees, great whites are a feast of complex behaviors—maddeningly coy in their breeding habits and wary but stunningly accomplished killers. Remarkably, they also are now listed as endangered, and when an apex species is in trouble the threat can cascade down through the entire food chain.

For years close encounters were pretty much out of the question. Swimmers and scuba divers ardently avoid the sharks, and useful observation in study tanks or aquariums is impossible because the animals do not survive prolonged captivity. But recent growth in the popularity of shark-cage diving has opened new opportunities. On this August morning Horizon’s crew, scientists and ecotourists are arriving under the aegis of Shark Diver, a leading operator of “sharking” excursions to Guadalupe. The mission, as always: to watch at close hand this impressive animal in its natural surroundings.

Shark Diver, in conjunction with the Marine Conservation Science Institute, has identified, recorded and named more than 85 individual great whites that regularly return to the area, now a reserve protected by the Mexican government. A compilation of photographs (including contributions from amateur cage divers) plus tagging and satellite tracking is steadily producing a detailed profile of the Guadalupe community of great whites. A thick ring binder, the “family album,” circulates in Horizon’s wood-paneled saloon. Among the pictured sharks are Fat Tony (the charter member of Shark Diver’s roster), Nacho, Belt Strap, Bruce, Captain Hook, Harvey, the Russian. And the truly massive 18-foot females that migrate here late in the fall—Tlazolteotl (named for an Aztec goddess), Chicka, Dorri, Snow White, Lady Notch—many of them pregnant and voraciously hungry.

Even though the great whites are a protected species, relentless poaching has put them on the international “threatened” list. Shark Diver CEO Patric Douglas reports that one set of jaws alone can fetch $5,000 in Ensenada. His Guadalupe Island Conservation Fund (www.guadalupefund.org) has documented the sale of whole carcasses of the great white for $20,000 on the black market. Mexico’s national park service lacks the resources to station patrol boats at Guadalupe during the great whites’ season. But Shark Diver expedition vessels, along with those from several other adventure operators, have become an unofficial police presence against illegal sport fishing.

The great white shark will always be the subject of controversy, in large part because of Peter Benchley’s best-selling thriller Jaws and the movies it spawned. Two years before his death in 2004, Benchley boarded Horizon for his own Guadalupe visit. He wanted to see firsthand the creatures he had demonized. By that time Benchley was already an advocate for white shark conservation, having seen the senseless, bloody orgy of shark hunting touched off by his success. He was profoundly moved by the majesty of these animals, and his campaign to save them soon took hold in the media. Ecotourism now helps to fund great white conservation.

Sympathy for the great white shark should never obscure its important role as a predator, however. Luke Tipple, a respected shark biologist and Shark Diver’s director of operations, is outspoken on this subject. “Occasionally,” he muses, “you’ll hear the phrase that great whites are ‘misunderstood.’ They may have been mistreated, but they are definitely not misunderstood. Many millions of years of evolution went into producing this animal, and he is, first and foremost, an astonishingly efficient killer. Let’s not take that away from him.”

Watch a shark slide show here:

Article taken from this months Scientific American Earth 3.0

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