Whale scientist Palumbi transforms controversy into conservation
This Bryde’s whale is one of several hundred whales harvested for scientific research in Japan annually.
The population of humpback whales, before the rise of 19th century commercial whaling may have been 10 times bigger than previous estimates, according to Stanford geneticists.
Steve Palumbi is no stranger to controversy. A professor of biological sciences at Hopkins Marine Station, Palumbi incurred the wrath of the Japanese whaling industry more than a decade ago by conducting the first genetic study of whale meat sold in Tokyo food markets.
Japan harvests more than 300 Antarctic minke whales every year for scientific research. The Japanese government, arguing that minke whales are relatively abundant, allows the slaughtered giants to be sold as food.
In the early 1990s, conservationists began to suspect that threatened and endangered species also were being commercially exploited. To find out, Palumbi decided to analyze samples of DNA from whale meat randomly purchased at local Japanese markets. The results, published in 1994, revealed that, in addition to minke whales, retailers were selling food made from humpbacks and other protected species, for as much as $100 a pound. Palumbi's findings were immediately denounced by the Japanese whaling industry, but the government of Japan eventually adopted his techniques and began conducting its own DNA tests to prevent future sales of contraband whale meat.
"The most important thing is to establish a dialogue," says Palumbi, noting that commercial whaling nations, such as Japan and Norway, are more likely to heed the warnings of conservationists whose conclusions are backed by solid science. "New technologies are providing a much more refined picture of whale biology today than we've ever had," he notes.
On Feb. 20, Palumbi and other marine scientists discussed some of these technological innovations at a symposium titled "What Cousteau Never Knew About Whales: New Technologies Reveal Surprising Tales," at the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington, D.C.
Controversial scienceDuring his talk, Palumbi explained how recent advances in genetics have helped revolutionize whale research while sometimes sparking controversy.
The most recent firestorm began in July 2003, when the journal Science published a study on humpback, fin and minke whale populations co-authored by Palumbi and graduate student Joe Roman. Using DNA analysis, Palumbi and Roman concluded that the worldwide population of humpbacks, now estimated at 20,000, might have been as been as high as 1.5 million before commercial whaling took off in the 1800s. That figure is more than 10 times bigger than the widely accepted historical estimate of 100,000 humpbacks, which is based on 19th-century whaling records.
In their study, Palumbi and Roman analyzed maternally inherited mitochondrial DNA samples from hundreds of humpback whales. They discovered that the DNA sequence in a gene called "D loop" varied widely among individual whales.
"A small population tends to weed out all of its genetic differences through inbreeding," Palumbi notes. "A large population should have a lot more genetic variation. Our study shows that humpback whales today actually have about 10 times more genetic variation than would be expected from previous estimates of their populations."
This finding caused an uproar among researchers who have long relied on whaling records to calculate historical populations. Some critics said that Palumbi's estimate of 1.5 million humpbacks was not "remotely realistic," while others took strong exception to his assertion that whalers' logbooks might be incomplete and unreliable.
The Science study also sent shockwaves through the International Whaling Commission (IWC), a consortium of 51 countries that regulates the whaling industry worldwide. In 1986, the IWC declared a moratorium on commercial whaling—a position respected by all member-nations except Japan and Norway. The IWC can allow commercial hunting to resume in areas where a population has reached 54 percent of its original carrying capacity. But if Palumbi and Roman's estimate is correct, the number of humpbacks would have to increase dramatically before whaling could resume.
Frightening yet productiveSoon after the Science study appeared, Palumbi was invited to speak before the IWC's scientific committee at the commission's 2004 meeting in Sorrento, Italy. "That was the most significant and frightening event I attended last year, but it turned out to be very productive," he recalls. "When you surprise a regulatory agency with a new point of view, it shouldn't come as a shock that they are cautious. The IWC wasn't ready to take the genetic results and turn them into policy, but a roadmap was laid out."
Committee members raised numerous questions about the Science study and criticized Palumbi's decision to rely on genetic variation in just one gene, D loop, which has a complicated mutational history that can be difficult to interpret. In response, Palumbi and his Stanford colleagues have launched the first multi-gene whale population study that will allow researchers to compare DNA variation in 11 different genes.
Palumbi also is re-visiting the portion of the 2003 Science study that focused on Antarctic minke whales. It turns out that New Zealand geneticist Scott Baker conducted an independent analysis of minke whale DNA using both the D loop gene and another mitochondrial gene called cytochrome b.
"We wanted to see if cytochrome b—a different gene with much nicer mutational characteristics than D loop—was going to give us the same answer," Palumbi says. "Amazingly, we got the same estimate no matter which gene we used: The historic population of the Antarctic minke whale was about 1 million." The IWC estimates the current population at somewhere between 510,000 and 1,140,000, but these numbers recently have been called into question.
The minke whale samples used by Palumbi and Baker were obtained from meat markets in Japan, although they were originally slaughtered for "scientific research." The irony, says Palumbi, is that the genetic research could have been conducted without harming a single whale. "DNA data can very easily be obtained from a harmless skin biopsy," he adds, "so no one needs to kill them and sell them into a meat market."
Family treesPalumbi used the AAAS symposium to address "the next chapter in this controversy, and what we're trying to do to solve it. In the last 12 months, we've gotten a much better set of mathematical and analytical tools for taking genetic diversity data and turning them into past history and past population size."
According to Palumbi, these new tools will allow researchers to use DNA sequencing to construct cetacean "family trees."
"The shape of that family tree tells us a lot about how the population has changed over time," he explains. "The parts of the tree that bulge out mean that the population was bigger and doing well at that point in the past. The parts that narrow down are points in the past where the population has shrunk. Think of those family trees of royal houses in Europe, where one queen has 12 children, so it bulges out there, but none of the children do very well, for various reasons, so the tree collapses back down again."
The same holds true for whale genealogies, he adds. "We're able to read back in time and see how the population changes. We're hoping to see if, as the ice ages come and go, whether the populations dwindle and then come back up again. Our hope is to be able to use this as a tool to see how whale populations have responded to climate change in the past, and perhaps that will give us a hint about how whale populations will respond to climate change in the future."
The IWC also urged researchers to reconcile the dramatic differences between population estimates based on genetics versus whaling records. "What we've tried to do ever since the furor over the Science paper started is to engage historians by saying, let's try to figure out if there is an answer that is supported by both of our techniques and come to some agreement," Palumbi says. "Most historians seem to agree that the previously accepted numbers were too low, but not as high as we've said," noting that researchers at the Woods Hole Oceanographic Institution in Massachusetts are reexamining old whaling logs in light of the recent genetic findings.
Other speakers at the AAAS symposium were Christopher Clark of Cornell University, who described advances in whale bioacoustics; Roger Payne of Ocean Alliance, who discussed how toxicological studies of sperm whales are improving our understanding of ocean pollution; and Craig Smith of the University of Hawaii, who presented new studies showing how dead whales support invertebrate life on the seafloor.
"If filmmaker Jacques Cousteau could climb out of his grave and go to a seminar, it would [have been] this one, because when he made his last whale movie, he knew about whales only what he and others could see," Palumbi concludes. "Now we know a huge amount that he never knew, because of all this new technology. As a result, we can not only manage them better, but, as Roger Payne is trying to do, we can use them as a gauge of how the oceans are doing. And that, fundamentally, is going to affect us all."