Demon Fish (27 page)

When Pikitch first came to the country in the mid-1990s, she rarely saw sharks at the market, which she regularly visits to buy bait. Belizeans don’t particularly crave shark: the fish only started showing up for sale once the shark fin market began to boom in the late 1990s. In 2005, Pikitch was concerned to learn that a nurse shark—which has relatively small fins, and therefore fetches just a modest price—was for sale at the market. As the demand for fins has risen, fishermen are going to any lengths possible to bring sharks to market to take advantage of the high prices before they disappear.

“I just gasped, because that is really scary,” she says, as we prepare to head out on our fish shopping trip in Belize City. “The sharks are starting to go.”

——

While Pikitch and her team can handle most of the sharks in Glover’s Reef with relative ease, not all sharks can be monitored by swinging a lasso around them and surgically implanting an acoustic tag. Given that whale sharks are roughly the same size as a school bus, it’s not easy to haul one of those fish over the side of their boat and cut it open. This is where the slingshot comes in.

One of the best places in the world to spot whale sharks is off Isla Holbox, site of a former pirates’ cove off the Yucatán, lying roughly ninety miles northwest of Cancún. At this point Isla Holbox, a sleepy tourist town whose only motorized vehicles are golf carts, has become a critical research location where American and Mexican scientists are seeking to determine the migration patterns of sharks that cross national borders regularly as they traverse the Mesoamerican reef.

Robert Hueter, from Mote Marine Laboratory, spotted his first whale shark in 1975, when he was a graduate student at the University of Miami and a whale shark managed to make its way up Florida Bay. The whale shark eventually disappeared, and a week later it was found dead. Hueter didn’t spot another for a quarter century.

He started coming down to Isla Holbox back in 1994. At the time, he was researching blacktip sharks, which gave birth in one of the island’s secluded lagoons. After nearly a decade some of the locals informed Hueter that in late May and early June—just after he would leave town to return to Florida—a posse of whale sharks would come into the region. Curious, he helped convene a group of fishermen, activists, and Mexican and American scientists to determine what was happening.

Like Pikitch, the survey Mote scientists have constructed with researchers from Proyecto Dominó, a Mexican-based conservation group, seeks what amounts to bare-bones information about the sharks that arrive at the start of each summer and depart by the time fall arrives. What does this animal population look like, why do they come here, and where do they go when they leave? Rafael de la Parra, who heads Proyecto Dominó (the locals coined the nickname
dominó
for whale sharks because of their many spots), says he and his colleagues can’t expect to protect the sharks if they don’t have a clue about how they operate. While shark researchers are using some of the most sophisticated scientific techniques that now exist for tracking their subjects’ movements, they are starting from a base of knowledge that lags decades behind their terrestrial counterparts. All that, and in order to get any work done, they have to aim a fancy slingshot at a beast that could easily crush them.

At first glance, Rafael de la Parra doesn’t look like much of a spear carrier. De la Parra—who generally goes by Rafi—is a somewhat portly, middle-aged Mexican in a black Speedo and snorkeling mask, holding a tagging spear. He boasts a beatific smile nearly all the time, except when a given tour operator pisses him off. Then he glowers.

But right now he is smiling, because we have spotted a congregation of whale sharks, and he’s ready to dive in. He has a clear goal in mind: jump in the water and deploy the elastic band on his metal pole as soon as he gets within striking distance of the shark, which is about three feet away. At that moment, once he’s angled it properly, he releases the elastic with his thumb so that the tag will shoot forward and attach itself to the side just below the fish’s front dorsal fin. De la Parra can accomplish this feat in a matter of seconds, with the ease of an expert javelin thrower.

With little warning, de la Parra slips off the boat and heads toward the massive polka-dotted animal that’s swimming alongside our vessel. I scramble in after him and manage to get close enough to see him fire the tag into the shark’s body. De la Parra is within reach to determine the fish’s sex: as he pops up on the surface, he shouts, “Macho!” before submerging once again.

De la Parra has done this dozens of times: at this point researchers have tagged more than seven hundred whale sharks in the region since they started studying them in earnest in 2003. In fact, tagging whale sharks is the least difficult part of their job: Hueter, who has personally tagged at least three thousand sharks over the past thirty years, says whale sharks are easy targets. “In a thirty-foot long shark, they don’t even flinch.” But once they’ve gotten an animal tagged—especially if they’re using a satellite or acoustic tag—the challenge begins.

On this particular afternoon, for example, I’ve joined de la Parra, Hueter, and another Mote senior biologist, John Tyminski, as they track the path of the shark to which de la Parra has affixed an acoustic tag. Standing by the tracking equipment, Tyminski recaps what we’ve done today when it comes to placing the tag on the shark. “At 13:20, we put it in a mature male seven miles north of Cabo Catoche, ten nautical miles north of Cabo Catoche point.” The biologist can also record water the shark started cruising in once it was tagged—it’s 78.96 degrees Fahrenheit, composed of 14.4 percent dissolved oxygen. But where’s the shark now?

Nowhere to be found. Apparently, something has gone wrong. We circle the water in broad loops for hours, hoping to pick up a signal from the tag, which conveys a high-frequency beep every second to a hydrophone the scientists are monitoring on the boat. If the animal is within thirty-seven miles of the tracking equipment, the researchers should be able to use the hydrophone to determine which direction the sound is coming from, and thereby keep track of the shark. But in this case, either the shark is an extremely fast swimmer or the equipment—a $650 acoustic tag with a depth sensor—has failed. We are practically, as Hueter explains, “looking for a needle in a haystack.”

“Active tracking has never been one of my favorite things to do,” he says, as the afternoon wears on and the sun continues to beat down on us. “Even when it works, it’s very tedious.” And, in this case, it’s not working.

This is the fundamental problem with shark tracking: it’s costly, complicated, and unreliable, even though it’s essential to understanding these ocean predators. Rachel Graham of the Wildlife Conservation Society uses three different methods to monitor the whale sharks she tracks: photo identification (each whale shark has a unique spotted pattern), satellite tags, and acoustic tags. Back in 2000, Graham placed the first pop-up satellite archival tag on a whale shark. These instruments contain a miniature computer that measures pressure, light, and temperature. This combination of measurements gives scientists a precise sense of where the sharks are traveling, in terms of not just latitude and longitude but also depth. Researchers like Graham program the tags for a set period of time, and when they pop off the animal, they transmit streaming bytes of data to an earth-orbiting satellite, providing a snapshot of what the shark was doing at a given point in time.

These tags can provide a treasure trove of information. Once Graham, diving with her husband, Dan, spotted an archival tag she needed to recover. “Get that tag!” she screamed. (They were underwater, but he got the point.) The tag offered up 206 days of information on what a whale shark had been doing—including diving to unprecedented depths of nearly five thousand feet.

And while Hueter and his colleagues have lost tags on many occasions, the ones that have stayed on have provided promising clues to where whale sharks travel when no one can see them. For years, scientists have suspected the animals give birth in remote areas of the ocean, because no one has spotted their young off the Atlantic coast. In 2007 his team attached a satellite tag to a twenty-five-foot-long female with a rotund belly they nicknamed Rio Lady. Over the following 150-day period, the whale shark traveled nearly five thousand miles from the Yucatán Peninsula through the Caribbean Sea to south of the equator between Brazil and Africa. The area where she ended up, north of Ascension Island and south of St. Peter and St. Paul Rocks, is remote but full of marine life, including sea turtles, billfish, and other sharks. Hueter believes he’s found one of the whale sharks’ elusive pupping grounds, though it will take more research to verify whether that’s true.

Whether it’s satellite and radio tagging or genetic sampling, shark tracking has produced several of the most significant advances in how we understand sharks’ movements and their evolution. It is how we have come to know that great white sharks off the coast of California hover much closer to us than we previously thought.

To discover this, however, researchers such as the Stanford University graduate student Chris Perle had to spend plenty of time at sea, trying to retrieve the very tags they attached to sharks in the first place. Perle was out on the water on a sunny mid-October afternoon in 2006, while I was interviewing his adviser, the Stanford University marine sciences professor Barbara Block.

Block, who works out of the Hopkins Marine Station in Monterey, is the unquestioned queen of shark tagging. She has worked with a group of collaborators to pioneer the Tagging of Pacific Predators program, which has tagged more 4,300 predators from twenty-three species since 1999. That includes great white, salmon, thresher, blue, and mako sharks, along with a wide assortment of seals, whales, seabirds, and tuna. Tagging a great white shark involves an elaborate procedure featuring a seal decoy, which researchers use to lure the shark close to their boat. As Block puts it, “It takes incredible man and woman hours to do that kind of work.”

Even though she’s been doing this work for several years, Block can’t help marveling at how the high-tech tags help her keep track of elusive sea creatures. “You can, in real time, see where a shark is on the blue planet,” she explains as she points out the tracks the great white and salmon sharks have made according to satellite data. “I wake up every day, get my cup of coffee, and see where my sharks are.”

The promise of that modern marvel is what had Perle searching for a small, titanium-encased, seawater-resistant item awash in the Pacific Ocean. The day before the tag had popped off a female great white shark’s fin, to which it had been attached for three hundred days. Despite having its rough coordinates and $7,000 worth of monitoring equipment in hand, Perle and his colleagues couldn’t locate it. So he called Block for advice.

Block checked her computer, rattled off a few coordinates to Perle via cell phone, and then explained she and her researchers were “throwing everything we’ve got at this,” even though it amounted to “a small thing in a big ocean.” And, as she admits, most of the time the scientists are making it up as they go along. No one has ever tried to track animals, when they are not visible, on this global scale. Block describes it as “constructing mission control” for the sea.

Sometimes the researchers at Hopkins Marine Station get lucky, since if ordinary citizens stumble upon a tag they often return it in exchange for a $500 reward. One woman recovered one of Block’s pop-up tags in Hawaii, while another time a five-year-old named Calvin Wisner discovered one while walking on the beach with his parents near San Francisco just after Christmas in 2005.

For Perle, no such luck. It turned out the radio signals from the tag were bouncing off local cliffs, making it impossible for him to pinpoint exactly where it was, and on top of that it drifted twenty-five miles down the California coast in the course of a week. Still, Perle persisted, walking along the cliffs himself in order to scan the shore and the sea.

He found the tag, but got such a serious case of poison oak from his beach walk—“the worst case of poison oak in my life”—that he landed in the emergency room, and it took him a month to recover.

Block has not only managed to tag dozens of great whites off the Pacific coast; she’s helped establish an elaborate acoustic receiver system that lets her and other researchers know where the sharks are migrating along an aquatic corridor between California and Hawaii. This project has provided Block with one of her most astounding finds: white sharks stay much closer to U.S. shores for a longer period of time than anyone realized, and in greater numbers.

Block, working with researchers such as Stanford University’s Salvador J. Jorgensen, used either satellite, acoustic, or mitochondrial DNA tags from a total of 179 white sharks over the course of eight years to prove these creatures were not wandering aimlessly in the open ocean. Deploying a decoy made out of carpet that resembled a seal’s silhouette, they attracted great whites to their boat and inserted the tags with the aid of a 2.3-inch titanium dart and a lance. Many of these tags managed to track a shark’s movements for an average of six and a half months; one did it for just over two years.

Since great whites are capable of traversing vast ocean basins, scientists had thought they would explore large swaths of the sea rather than stick to a single pattern. But to their surprise, they discovered that they migrated in the same sort of predictable, long-distance route year after year, like pronghorn antelope on land and purple martin songbirds in the air. Each winter the animals left the central coast of California and headed between 1,240 and 3,100 miles offshore, along the Hawaiian archipelago. By August, they had returned. While foraging off the California coast, the sharks tended to congregate around certain “hub spots,” including the entrance to San Francisco Bay and off Carmel Point, a popular beach.
¹⁹

These migrations are so regular, in fact, that the white sharks of the northeast Pacific have become genetically distinct from two sets of counterparts on the other side of the ocean, one close to Australia and New Zealand and another off South Africa’s coast. There are no visible differences between the whites swimming off California’s coasts and those on the opposite side of the Pacific: Carol A. Reeb, a research associate in Block’s lab, was able to make the determination by examining differences in mitochondrial DNA, which mothers pass directly to their offspring through the egg. Reeb estimates that the great whites circling close to San Francisco likely descended from migrants that came from the other side of the Pacific during the late Pleistocene, between 150,000 and 200,000 years ago. And Mahmood Shivji, who works for the Save Our Seas Shark Centre in addition to the Guy Harvey Research Institute, has used DNA analysis to determine that almost all species with global distributions have distinct genetic populations within individual ocean basins.