Page last updated at 11:49 GMT, Thursday, 26 June 2008 12:49 UK

Counting whales: A fluky business

By Richard Black
Environment correspondent, BBC News website, Santiago

Close up and personal

In an era when we can track the lineage of humanity using DNA and monitor deforestation from space, you might think scientists would have come up with a more sophisticated way of counting whales than standing on the bridge of a ship with a pair of binoculars.

If so, you would be wrong - mostly.

Many decades after they were first used, sighting surveys are still the standard way of estimimating how many whales there are in the oceans.

"There are many variables that can affect your ability to see whales - that can include obvious things like weather, ice conditions, depending on where you are," says Greg Donovan, the genial Irishman who heads up the scientific programme of the International Whaling Commission (IWC), the global body charged with regulating whale hunting and conserving the giant cetaceans.

"But essentially, you look hard until you see either a blow or a body; and then you record it, plus the distance and the angle to where you see it."

One of the committee members said he knew of no other scientific endeavour where the main data item was guessed
Vassili Papastavrou, Ifaw

Counting whales should matter, wherever you stand on the rights and wrongs of hunting.

Good estimates would be needed for setting quotas if commercial whaling should ever be revived - as appears to some degree possible, now that the IWC has decided at this year's annual meeting to embark on a process of reform, perhaps leading to compromise.

They are needed to set quotas for the subsistence hunts performed by indigenous peoples in Greenland, Russia, the US and the Caribbean; and they are definitely needed for conservation.

So if this is the case - and the IWC is just one body putting resources into gathering numbers - why is it that estimates for some populations are so imprecise?

Gray areas

Some species can be counted easily.

Gray whales and bowheads follow set migration routes and can be counted from shore; the individual patterns of tails help identify humpbacks, producing better estimates.

But for the species most hunted today, the minke, sightings from ships - sometimes augmented by aerial surveys - are just about the only option.

Right whale. Image: BBC

The IWC puts the Southern Ocean minke population as anywhere between 510,000 and 1,140,000.

But that estimate dates from the 1980s; and despite reams of data gathered since and hints of a decline, the scientists have yet to agree a more up-to-date figure.

For minkes off the west coast of Greenland, the estimates run from 3,600 to 32,000 - a huge margin of error. A factor of five separates the lowest and highest possible estimates of the fin whale population in the same area.

"If you think about what we're trying to do, we're trying to estimate numbers of animals that spend very large parts of their time completely out of sight," says Mr Donovan.

"So I don't think people should be surprised (that we don't have more exact numbers). The important thing if we want to use this for conservation is that we don't over-estimate; in a sense, under-estimating is a better mistake to make."

Starting line

Apart from the weather, which can get in the way of any observations, there are other limitations to how accurate surveys can be.

"One of the potential error sources is that because we're humans, there are of course individual differences between skills or capabilities to observe," says Yoshihiro Fujise, director of Japan's Institute of Cetacean Research (ICR), whose ships the IWC uses for its annual Antarctic sighting expeditions.

"So to minimise that error we rotate the observers. On the research vessel, we place five to six observers on the upper bridge; and then we place more still higher up in the vessel, and all the observers use binoculars so they can see the whales."

Ocean spray

Before a survey starts, a course is plotted which is designed to give representative coverage through the area being studied, often in a zig-zag path.

"The whales are in the survey area, wherever they want to be; and what we do is we cover the area as specified by the course line so we will encounter the whales in a manner which is fairly random," says Dr Fujise.

But there are limitations. The vessels usually used in the Antarctic are not ice-strengthened, so they cannot go close to the ice edge, which may be a productive feeding ground for species like the minke that eat krill.

Vassili Papastavrou, a whale biologist with the International Fund for Animal Welfare (Ifaw), has issues with the basic methodology.

"Some of the whales in your path will be underwater when you go past, so you won't see them," he says.

"Whales that are further away from the boat are less likely to be seen than ones that are close to the boat; and in the case of some species, we think they might react to the boat."

His main concern is that observers have to estimate the distance between the boat and the whale they spot - a vital component of the data, but something, he says, that humans are just not very good at.

"And many years ago, at a scientific committee meeting of the IWC, one of the committee members said he knew of no other scientific endeavour where the main data item was guessed."

To groups such as Ifaw, the population uncertainties represent one more reason why commercial whaling should stay banned.

Managing uncertainty

Over the years, researchers have developed computer models designed to turn these uncertainties and the raw numbers of whales sighted into a reasonably truthful picture of what is known and what is not.

You don't have to have a PhD in biology to realise that taking 40 animals from such a large population is not going to have any measurable impact
Stefan Asmundsson
Iceland's whaling commissioner

In essence, the models gauge the likely scale of the uncertainties, generating what Donald Rumsfeld might have called "a half-known unknown".

"The most important component, particularly if you're not looking for an abundance estimate for a coffee-table book but for management, is that you capture all the uncertainty there is," says Greg Donovan.

"I can't tell you how many whales there are in a particular area. What I can say is the likelihood is that it lies between this number and that number; and anyone who tells you there are exactly 4,623 whales somewhere is lying."

Taking precautions

Faced with these uncertainties, how safe is it to set catch levels at all?

The IWC believes in principle it is possible, and does set them for subsistence whaling.

On the commercial whaling side, quotas higher than zero would imply lifting the 1986 global moratorium; so even though a mechanism exists for setting them, none have been.

Under the global moratorium on commercial whaling, hunting is conducted in three ways:
Objection - A country formally objects to the IWC moratorium, declaring itself exempt.
Example: Norway
Scientific - A nation issues unilateral 'scientific permits'; any IWC member can do this.
Example: Japan
Aboriginal - IWC grants permits to indigenous groups for subsistence food.
Example: Alaskan Inupiat

Norway, Iceland and Japan - the three active hunting nations - set their own quotas, to a greater or lesser extent using the IWC's methodology.

"We set all quotas on the basis of the precautionary approach, and all uncertainties are taken into account," says Iceland's whaling commissioner Stefan Asmundsson.

"And if you look at, for example, where you have a stock size which counts tens of thousands and we're taking 40 animals, you don't have to have a PhD in biology to realise that taking 40 animals from such a large population is not going to have any measurable impact."

In fact, he says, Iceland's politicians have tended to set quotas below the limits suggested by its scientists - a very different picture from many commercial fisheries, such as the North Sea, where governments routinely force quotas above and beyond what scientists say is wise.

Sudden surprise

But Iceland also provides an example of the limitations of trying to measure population sizes.

Over a five year period between 2001 and 2006, its minke whale population apparently declined by 75% - a huge fall in such a short space of time.

Probably the minkes just went somewhere else in search of food.

But that is not certain. Proving it would need more data, more sightings, and more expeditions than anyone is prepared to pay for.

As Greg Donovan emphasises, it is an expensive business.

"I'm in the process of working with other colleagues to design a full survey of the Mediterranean and the Black Sea.

"That's going to require something like 14 boats, three aeroplanes, and well over 150 researchers; but it's important, because fundamental conservation science requires good information on numbers."

Can other methods come in and fill in the gaps in the sighting record?

For some species, acoustic methods are definitely an option. The sharp clicks generated by sperm whales can be tracked, counted and archived using simple sonar arrays.

It is much more difficult for species such as humpbacks and blue whales, with their meandering songs.

Satellite imagery does not yet have sufficient resolution, though Ifaw has been trying to interest at least one major IT company in looking at the possibilities.

So the chances are that if you head down to the Southern Ocean in 10 years' time, you will still find old-fashioned human observers out on deck scanning the seas for whales.

You will still find estimates for some whale populations that are full of uncertainties.

And you will still find people arguing about whether that means it is safe from an ecological point of view to hunt whales.

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