Some types of whales were far more common that is typically thought before the hunting frenzies of the 19th and early 20th centuries began to wipe them out, a pair of geneticists said Thursday.
Studying the DNA of three types of whales inhabiting the Atlantic Ocean, the scientists decided that today's whale numbers must be based on historic populations at least 10 times the numbers normally accepted.
The findings could put pressure on the International Whaling Commission (IWC), which has banned whaling for 17 years except in limited circumstances. The IWC says that whaling of any particular species cannot be resumed before populations reach at least 54 per cent of their historic levels.
Those levels have been calculated largely based on 19th-century records, but scientists from Stanford and Harvard now say that the IWC's historic numbers are wildly inaccurate.
Instead of using old data, which they say may be unintentionally or intentionally incomplete, Stephen Palumbi and Joe Roman studied the DNA variance of three types of whale.
"The genetics of populations has within it information about the past. If you can read the amount of genetic variation — the difference in DNA from one individual whale to another — and calibrate that, then you can estimate the historic size of the population," Stanford's Stephan Palumbi said. "A small population tends to weed out all of its genetic differences through inbreeding; a large population, by contrast, should have a lot more genetic variation."
The numbers they came up with — and which will be published in Friday's edition of the journal Science — are dramatically different than those the IWC uses.
According to the IWC, humpback whales in the North Atlantic peaked historically at about 20,000. They also believe that fin whales in that area once numbered 40,000 and that there were about 265,000 minke whales. Although fin whales now number about 56,000 (which would thus be considered a historic high), humpback and minke whale populations have dropped by about 50 per cent, by IWC estimates.
Dr. Palumbi and Mr. Roman say that, based on the amount of variance displayed by the DNA of these whales, their historic populations had to have been dramatically higher. They say that there were instead as many as 240,000 humpback whales and 360,000 fin whales in the North Atlantic alone. Their analysis of minke numbers suggested that, with regard to that species, IWC estimates are closer to an accurate number.
Using Dr. Palumbi and Mr. Roman's new conclusions, populations of fin and humpack whales have plummeted to lows of between 4 and 15 per cent of their historic highs.
"Somehow we have to reconcile [the] numbers," Dr. Palumbi said. "That's going to require going back and looking at the whaling records. Are they complete? Have there ever been large hunts of whales that weren't recorded? These are things that we have to find out."
The two geneticists are not ignorant of the importance of their findings to the debate of how, when or if to operate a commercial whaling industry.
"The question is, when is a population large enough to allow whaling to begin? That depends upon how many whales there used to be before whaling wiped them out," Dr. Palumbi said. "This is a real conundrum.
"Humpback whales, for example, were thought to have numbered about 20,000 in the North Atlantic, and we're 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 wouldn't be able to start whaling for another 70 to 100 years."
