Scientists have underestimated the number of humpbacks and other great whales that inhabited the North Atlantic Ocean before the advent of whaling, according to geneticists from Stanford and Harvard Universities.
The findings, published today in the journal Science, could cast grave doubts on the scientific rationale used by countries that advocate lifting a 17-year moratorium on commercial whaling established by the London-based International Whaling Commission (IWC), the scientists say.
The IWC, which is the main organization that regulates whaling, has policies that will allow for the resumption of commercial hunting when populations reach a little more than half of their historic numbers.
But the findings of the new study expose a problem with this policy, which relies on historic estimates of unconfirmed whaling records dating back to the mid-1800s, says Stephen Palumbi, a professor of biological sciences at Stanford and co-author of the study.
"It is well known that hunting dramatically reduced all baleen whale populations, yet reliable estimates of former whale abundances are elusive," wrote Palumbi and Harvard graduate student Joe Roman, lead author of the study. "Whaling logbooks provide clues, but may be incomplete, intentionally under reported or fail to consider hunting loss."
Roman and Palumbi say their study is the first to use genetics rather than whaling records to confirm the number of whales that used to exist.
The scientists focused on the genetics of North Atlantic humpback, fin and minke whales – three species decimated in the mid-19th and early-20th centuries by the demand for whale oil, baleen and meat.
"The genetics we have done of whales in the North Atlantic says that, before whaling, there were a total of 800,000 to 900,000 humpback, fin and minke whales – far greater numbers than anybody ever thought," Palumbi said.
Comparing DNA samples from 188 humpback whales, Roman and Palumbi determined that the historic population in the North Atlantic may have been 240,000, some 12 times greater than the IWC estimate.
Using these results, Palumbi estimated that the worldwide humpback population could have been as high as 1.5 million – more than 10 times the IWC’s global historical estimate of 100,000.
After analyzing DNA samples from 87 minke whales, the scientists concluded that the pre-whaling North Atlantic minke population was at least 265,000. This is roughly twice the number of minkes that inhabit the North Atlantic today, according to the IWC.
Reconciling these number is an essential component of future whale conservation, Palumbi says.
Under the current policies of the IWC, which declared a worldwide moratorium on commercial whaling in 1986, a majority of its 51 members could lift the moratorium and allow whale hunting in regions where populations has reached 54 percent of its original carrying capacity.
"This is a real conundrum," Palumbi said. "Humpback whales, for example, were thought to have numbered about 20,000 in the North Atlantic, and we are up to about 10,000 now, so at that rate, the IWC could allow countries to start killing humpbacks within the next decade.
“But if the historic population was really 240,000, as the genetics suggests, then we would not be able to start whaling for another 70 to 100 years."
Roman and Palumbi write that in light of their findings, current populations of humpback or fin whales are “far from harvestable.”
Minke whales are closer to genetically defined population limits, they wrote, and “hunting decisions regarding them must be based on other data.”