Whale 'success story' questioned

Monday, 10 September 2007

A whale conservation success story, the recovery of the eastern Pacific gray whale, may not be quite what it seems.

Since the end of commercial whaling, numbers rose to about 20,000, thought to be the level they had been at before hunting began.

But a new study using genetic methods, reported in the journal PNAS, suggests pre-hunting numbers were much higher.

The scientists say climate change may be altering the whales' supply of food significantly.

Earlier this year, researchers noted signs that grays were showing distinct signs of malnutrition when they arrived at their winter breeding grounds along Mexico's Baja peninsula.

They raised the idea that this might be connected with climate change. But the prevalent theory was that numbers had risen beyond the maximum level which the ecosystem could support.

The new research challenges that idea.

"I think that when we see large-scale issues in the population, such as starving or malnourished whales, we should be looking to long-term climatic changes in their feeding grounds," said Liz Alter from Stanford University, US.

Stock take

A few hundred years ago, three separate populations of gray (or grey) whales lived in the oceans.

The Atlantic stock is thought to have perished in the first frenzies of commercial hunting. Later, the eastern and western Pacific populations almost followed suit.

The western stock, which lives along the eastern coast of Russia, is close to extinction once more, with development for oil and gas fields the prime cause. Numbers may be as low as 120.

But the eastern Pacific gray has supposedly seen rude health. It was taken off the US endangered species list in 1994, with numbers each year hovering about 20-25,000, which historical records from the whaling industry and computer models of population indicated was around the historical level.

The new genetic analysis, which Liz Alter's group has published in Proceedings of the National Academy of Sciences (PNAS), challenges this view.

By looking at variation in the animals' DNA, the team concludes there were once 76,000-118,000 grays in the Pacific.

Even if those numbers were split between the eastern and western stocks, this indicates that the population of the eastern gray today is well below the historical level.

The researchers themselves acknowledge that further analysis should be done to confirm their findings. In particular, they would like to have samples from the critically endangered western stock, but given its parlous health, this would clearly be a sensitive issue.

Confirmation could have implications for traditional, or subsistence, whaling.

Aboriginal groups in Chukotka in the Russian northeast are permitted to hunt 124 eastern grays each year to provide meat for their communities.

The Makah tribe of Washington State near Seattle is allowed a further five. Its hunting is currently suspended pending a domestic US legal settlement, though one gray was killed just this weekend, apparently without permission of tribal elders.

If historical numbers were much higher, that would imply the grays are not as robust as believed, which could lower these hunting quotas still further.