Demon Fish (22 page)

Paul Raymond, an NOAA special agent based in the Southeast who has worked with Shivji on nearly two dozen cases, calls the professor’s DNA analysis “a great asset.” Nearly a decade ago, when the United States imposed anti-shark-finning laws, Raymond went down to watch Victor Chang, a shark fin dealer in Daytona Beach, practice his trade. He brought along an ichthyologist to help him distinguish among the species that fishermen had hauled in and were offering up to Chang that day.

As Chang sorted the different fins according to their value, Raymond wondered why the dealer sitting before him seemed more capable of enforcing the law than he was. Chang knew how to distinguish among shark species because his livelihood depended on paying the right price for a given fish. Raymond, on the other hand, was suddenly saddled with the burden of making the same distinctions in order to determine if someone had violated the law—but he lacked the knowledge required to make such a judgment. Chang would deal them out like a deck of cards. “This is silky shark, this is dusky, sandbar, sandbar,” Raymond remembers. “He’d just squat down and sort them out, and write up an invoice and pay the fishermen. And I thought to myself, ‘He just did that, why can’t I? Because I’ve got these regulations to enforce.’ ” Now Shivji’s lab provides Raymond with the answers he needs.

Shivji’s students are also using their genetics knowledge to prove that shark populations are more genetically diverse than people might have thought, a finding that has serious implications for officials in charge of ensuring that species don’t go extinct. Jennifer Magnussen, for example, has developed a primer that in a single test will not only indicate if the shark in question is a sand tiger shark but also determine if that shark came from the northwest Atlantic—in which case it’s prohibited to harvest it. Another student, Christine Testerman, has found that porbeagle sharks in the Northern Hemisphere, which are in danger of being fished to extinction, are genetically distinct from those in the Southern Hemisphere. The upshot: you can’t just count on porbeagle sharks from the Southern Hemisphere repopulating the depleted sharks near the United States, because the two don’t interbreed. In the end, DNA doesn’t lie.

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Just as law-enforcement authorities have become increasingly focused on tracking illegal shark dealing, so have more academics. The Stanford University marine biologist Stephen R. Palumbi is a more flamboyant character than Shivji—the small ponytail gathered at the back of his neck pegs him as a child of the 1960s, and he belongs to a rock band called Flagella, which performs songs about achieving conservation goals, fishing out the sea, and slime. But Palumbi, who directs Stanford University’s Hopkins Marine Station in Monterey, California, is just as committed to cracking the genetic code that helps determine the path of the global shark fin trade. A few years ago, he doled out an assignment to a bunch of graduate and undergraduate students: after giving each of the students $25, he instructed them to make a day trip to San Francisco’s Chinatown and buy dried shark fins in one of the many apothecary and grocery stores there. With most of the fins costing between $250 and $500 a pound, the students could afford a fin measuring between eight and ten inches. The stores, in many ways, mirror their Hong Kong and mainland China counterparts, as glass jars of grayish fins stacked next to one another on the floor compete for customers’ attention with dried ginseng and mushrooms, while delicate white feathered shark fins selling for nearly twice the price occupy a place of prestige high up on the wall.

A baby boomer with an irreverent sense of humor, Palumbi combines a geeky passion for technology with keen understanding of pop culture. It’s not enough to send his disciples out into the world to see sharks strung up to dry; he wants to film the expedition and post it on the Web, and to use their finds to help construct an elaborate DNA database. Palumbi’s Web site features “Short Attention Span Science Theater”—short video clips that bring viewers along for the ride as he and his students investigate Chinese apothecaries or test whether “Pacific red snapper” is really a fish species. It isn’t, and in fact is a made-up name that markets use to peddle an array of different, less desirable fish.

While Shivji, in Palumbi’s words, is invested in creating “a set of tools that give you an instant answer,” so to speak, Palumbi takes a little more of a long-term, ivory-tower view of things. Palumbi is working up a hundred different protocols for a hundred different species: “a discovery-based tool versus a positive test tool.” In other words, Palumbi is trying to give academic researchers a way to identify every single shark fin with laser-like precision so they can chart their evolutionary path as well as whether they’re being illegally traded; Shivji is pushing to ensure the cops can nab a wrongdoer on the spot.

Palumbi is looking to broaden the academy’s understanding of how sharks have evolved, as well as construct a detailed and comprehensive chart of what makes each shark species distinct. He has pioneered similar genetic studies on whales and has used his findings to challenge the scientific assertions of pro-whaling forces. While he’s appalled at the paucity of data concerning sharks worldwide—“We didn’t have the global database that would say, ‘This is what these fins are’ ”—he admits that what he’s doing, at the moment, amounts to an academic exercise.

“Right now there isn’t any money in it. Is anyone going to pay me to do this? I don’t think so,” he acknowledges, comfortably ensconced in his sunny office, a stone’s throw away from the Monterey Bay Aquarium. “At this point the case for doing this is not quite obvious to everyone.”

Sitting in front of his office computer, he plugs a specific genetic sequence into it: sure enough, 1,146 bases begin to stream across the screen. The computer program he’s using takes sixty-three taxa and scans their family trees, to see where the shark in question fits into the evolutionary path. This sort of letter crunching can provide a lens into all sorts of groundbreaking scientific findings: what shark populations looked like before humans started hunting them in earnest, for example, and whether they’re poised to adapt quickly to the earth’s changing environment.

Palumbi is fairly confident of the answer: they’re not, because sharks evolve so slowly. While they’ve survived for millions of years, he explains, they’ve done so by sticking to a similar genetic formula.

“They have relatively little ability to adapt evolutionarily,” Palumbi says. Unlike some marine organisms that can change quickly in the face of intense environmental pressures, sharks have historically adapted “on 40- to 60-, or 100-million-year timescales.”

The genetic codes make it clear: just because sharks have survived for hundreds of millions of years doesn’t mean they’re well positioned to weather the most recent challenge to their existence.

One group of scientists, who are drawing on both Shivji’s and Palumbi’s work, have a grand vision of DNA mapping that will ultimately capture the most significant species on earth: they call it the Consortium for the Barcode of Life. A few years ago, only a handful of researchers were trying to assemble the genetic sequences of animals large and small. Now hundreds of them work on the project: they have already collected at least 300,000 records for 30,000 different species.

David Schindel, the consortium’s executive secretary, describes it as “a sort of telephone directory of well-identified specimens” that will allow scientists to quickly determine what species they’re examining. To ensure that it’s a universal genetic marker, they are constructing these codes from the same mitochondrial gene regardless of the species: cytochrome oxidase 1, also known as CO-1. Using this specific marker, which is located on the gene that serves as the powerhouse of the cell, allows researchers to distinguish among even closely related sharks with a high degree of precision: Robert D. Ward, a scientist at CSIRO Marine and Atmospheric Research in Hobart, Tasmania, along with two collaborators, examined 945 specimens from 210 Australian shark species and distinguished them with 99 percent accuracy.
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To assemble this barcode directory, researchers are—in some cases—lifting samples from plant and animal relics that have been lingering on dusty natural history museum shelves for decades. “It’s pretty remarkable how durable the DNA in specimens is proving to be,” Schindel says. “We’re using insect legs that are fifty, sometimes a hundred years old.”

Robert Hanner, a biology professor at Canada’s University of Guelph, coordinates the Fish Barcode of Life campaign, a subset of the overall barcode campaign. While the prospect of cataloging all the fish in the sea seems daunting—there are thirty thousand known fish species, and the number continues to rise—Hanner appears confident he’s up to the task. (And, as Schindel points out, they try to keep the project in perspective: “We’re not trying to do all species in all places.”) In order to do their work, Hanner asks for five specimens per species, across a shark’s geographic range. When it comes to elasmobranchs, which include skates and rays as well as sharks, the group has analyzed 6,074 specimens from 573 species, which means they’ve created barcodes for a little more than half of all known elasmobranchs. Many sharks are particularly easy to differentiate genetically because they developed so long ago, allowing them plenty of time to accumulate genetic mutations that distinguish one species from another.

“These are the early days,” Hanner cautions, adding that once it’s complete, it will represent “the biggest communal database for the molecular diagnostics of fish in the world.”

Assembling a global barcode for sharks and other fish, he suggests, will give researchers a quick fix on whether they’ve stumbled on something new. Ultimately, these scientists hope, researchers can venture out with a handheld DNA sequencer to assess what they’re encountering in the wild. “The value of barcoding is it can tell you very clearly, is this a match with something in your database, or is it an unknown?” Hanner says.

No such DNA sequencer exists as yet: Hanner believes private companies will be happy to develop it once they’re confident enough barcodes exist to make it financially worth their while. “It’s not until we develop the Yellow Pages so every species has a lookup number that these big companies are going to get interested enough to throw investment dollars at it,” he argues. “People will say, ‘This is a market opportunity that needs to be looked at.’ ”

In the meantime, however, Hanner and his colleagues have a long stretch of letter crunching ahead of them.

DNA analysis isn’t used just to solve criminal and taxonomic mysteries, however. Shivji and Demian Chapman—his talented former student—have employed it to explain one of the most puzzling shark appearances in years. How sharks mate and give birth is one of the biggest remaining mysteries about them; genetics provides one of the few solid clues to understanding shark reproduction.

On the afternoon of December 14, 2001, aquarium employees at Henry Doorly Zoo in Omaha, Nebraska, found themselves confronted with an inexplicable sight: a baby shark had suddenly materialized in their tank overnight. The day before the zoo had three bonnethead sharks: all of them were four-year-old females that had spent all but the first six months in captivity. These sharks had not reached sexual maturity, and there wasn’t any male for them to mate with in the tank. So the zookeepers puzzled over how one of them could have produced an offspring. Was it a prank, even though there was no sign of entry? Could one of the sharks have stored sperm for more than three years, which would have been an unprecedented act since this sperm has traditionally lasted for just six months inside a shark’s womb? Within twenty-four hours a stingray living in the tank had killed the baby female, severely rupturing its liver, so aquarium officials took the shark’s body out to preserve it, and wrote off the incident.

Over the years, however, other zoos experienced mysterious births similar to Henry Doorly’s. In Detroit’s Belle Isle Aquarium, a baby shark had appeared out of nowhere, and researchers reported similar findings from other institutions. These scattered reports of virgin births intrigued Chapman, who at the time was pursuing his Ph.D. at Nova Southeastern University under Shivji’s tutelage. Chapman wondered whether these unexplained appearances meant that sharks, like some birds and reptiles, were capable of parthenogenesis, or asexual reproduction. In 2006, Chapman called officials at Henry Doorly and asked them to send him small samples from the baby shark’s fin and from the three female adults. Then, working with scientists at Queen’s University in Belfast, where he was putting in a short stint, he conducted a blind test of the four sharks’ genetic makeup. Chapman, an ebullient New Zealander by birth, engaged in a bit of good-natured wagering with his colleagues on the final outcome of his hypothesis. “We were bidding pints of Guinness on what it was going to be,” he recalls now.

Within a matter of weeks the doctoral candidate had his answer: the baby shark (nickname: Jesus, despite being female) had exactly half as much genetic variation as one of the captive female sharks, meaning the shark had inherited an exact replica of its mother’s genes rather than getting half its genes from one parent and the other half from its father. The female shark had produced the baby on her own. After making the discovery, Chapman literally ran across the room in his lab to look at Irish scientific textbooks that detailed some of the instances where this has occurred in other species, such as rattlesnakes and the Komodo dragon. When an egg is formed in one of these creatures, the animal also creates three polar bodies, a form of waste material that is genetically identical to the egg. Most of the time, these polar bodies are eventually discarded. But in the case of parthenogenesis, one of the polar bodies fuses with the egg, forming an embryo with half the genetic variability of its mother.

Chapman, who is now an assistant professor at Stony Brook University working at the school’s Institute for Ocean Conservation Science, collaborated with Shivji and a Henry Doorly scientist to confirm the bonnethead’s virgin birth, and subsequently identified another such birth at a second aquarium with an entirely different species of shark. He sees this capacity for parthenogenesis as both an asset and a liability. On the one hand, it highlights how resilient sharks can be in the most unforgiving of environments, whether they are isolated in captivity or in the wild, if fishing has decimated their numbers to the point where few mating partners remain. “It just goes to show, life will find a way,” says Chapman, who published his findings along with Shivji and another colleague in the British journal
Biology Letters
. On the other hand, genetic variability is essential to a species’ survival, so sharks produced through a virgin birth don’t add as much to a population as normal offspring; a shark with half the genetic diversity of its parent will be less prepared to compete.