As many as 900,000 humpback, minke and fin whales probably navigated the waters of the North Atlantic before their numbers were decimated by commercial whaling in the mid 19th and early 20th century -- several hundred thousand more than previously thought, according to the study in the journal Science.

The discrepancy is important because the International Whaling Commission -- the body that regulates international whaling -- allows a resumption in commercial whale hunting when whale populations reach just over half their historic numbers.

That point may be soon approaching for certain species, according to current estimates. Those estimates are are based on whaling log books dating back to the mid-1800s.

"The perception is that whale populations are close to recovery levels because historic levels are imagined to be quite small," said Stephen Palumbi, a professor of biological sciences at Stanford University and co-author of the study.

But according to a population analysis carried out by Palumbi and a colleague -- which uses recent genetic data on North Atlantic whales and the latest computer modeling -- those estimates are wide of the mark.

Palumbi and his colleague, Harvard University researcher Joe Roman, suggest that the North Atlantic humpback whale population probably numbered 240,000 at its historic high point -- 12 times higher than the IWC's best estimate.

The researchers looked at the DNA of today's whales, factored in changes for mutations, and then calculated the original size of the gene pool to estimate past population sizes.

"Our study shows that humpback whales today actually have about 10 times more genetic variation than would be expected from the whaling logbook estimates," said Palumbi.

"That tells us that sometime in the past, the population of humpbacks was pretty big," he added.

With humpback stocks currently around the 10,000 mark, commercial whale hunters in Norway and elsewhere would have to protect the humpback population for another 50 to 100 years, according to the new analysis.

"In light of our findings, current populations of humpback or fin whales are far from harvestable," said Palumbi. "Minke whales are closer to genetically defined population limits and hunting decisions regarding them must be based on other data."

The study has a 30 percent margin of error, plus or minus, and further genetic analyses should be carried out, Palumbi said.

In the meantime a 17-year moratorium on commercial whaling should remain in place, he argued. The moratorium is observed by all nations except Norway and Japan.

TERRA.WIRE