TROUBLE is brewing in the waters off the Chukotka Peninsula in the far east of Siberia. In the past few years, the aboriginal whalers of the eastern coastline who hunt grey whales for meat have reported that an increasing number of the creatures they catch smell so foul that even dogs won't eat them. The few people who have tried the meat suffered numb mouths, stomach ache and skin rashes.

 


Whale meat may not be to everyone's taste, but it is lucky for the whales that the hunters spotted the problem. The reports have prompted an international effort to work out what is happening, not only to the whales but also to the ringed seals, bearded seals, walruses and the eggs of seabirds which - according to the local people - are giving off a similar smell. There is no firm answer yet, but it is clear that all is not well in the ocean.

The eastern North Pacific grey whale was once considered a conservation success story. Hunted almost to extinction in the 17th and 18th centuries, the species made a remarkable recovery after the International Whaling Commission (IWC) banned commercial hunting of grey whales in 1946. The population recovered from a few hundred to more than 20,000. Today, only small-scale subsistence hunting is allowed: aboriginal hunters have a quota of 140 grey whales per year, which is split between the Chukchi people of Siberia and the Makah people of Washington state.

Yet now, the grey whales seem to be struggling. Numbers have fallen to between 15,000 and 18,000, and some researchers are concerned that the trend of the past few decades may have reversed. The Chukchi hunters first noticed that something was amiss in the late 1990s, although older individuals say the problem goes back to the late 1960s and early 1970s. Now they estimate that around 10 per cent of whales are inedible. "The smell reminds me of medicine tablets, and nobody can eat such meat," says Gennady Inankeuyas, a whaling captain and chairman of the Association of Traditional Marine Mammal Hunters of Chukotka.

In 2003, a team of US and Russian toxicologists set about investigating the mystery of the stinky whales. Teri Rowles, a fishery biologist at the US National Oceanic and Atmospheric Administration (NOAA) in Silver Spring, Maryland, and Valentin Ilyashenko, Russia's representative at the IWC, obtained tissue samples collected and frozen by local whalers to analyse in their labs.

Their first hunch was that the smell was caused by industrial pollutants such as heavy metals, organochlorines and polyaromatic hydrocarbons accumulating in the whales' bodies. The analysis, however, suggested otherwise. While the tissue samples were packed with more than 100 volatile organic compounds, there was no significant difference between the concentration of artificial pollutants in stinky whales and non-stinky ones. "Our analysis does not indicate any anthropogenic contaminant that the whales might be ingesting," Rowles says. She cautions, though, that because the samples had been frozen for two years - while permits to export them to the US were arranged - some of the more volatile compounds may have been lost. The study did throw up other possibilities, however. Stinky whales' tissues contained significantly higher levels of a host of volatile organic compounds such as ketones, aldehydes and alcohols than non-stinky ones.


So what's going on? Some marine biologists think that higher levels of these compounds may be a sign that the whales' metabolism is changing, perhaps because of a fundamental change in diet. There is some evidence to support this idea: the whales normally stick to a diet of shrimp-like crustaceans called amphipods, but hunters have reported finding stinky whales' stomachs full of seaweed and cod.

What's more, Lee Cooper, an ecologist at the University of Maryland Center for Environmental Science in Cambridge, has shown that eastern North Pacific grey whales are foraging in different areas and upon different food than they used to.

This population of grey whales undertakes one of the longest migrations in the animal world, leaving breeding grounds in the warm lagoons of the Baja California peninsula in Mexico between February and April to head to summer feeding grounds in the Bering and Chukchi seas (see Map). But according to Cooper, some whales no longer make the journey all the way north, stopping off instead around Kodiak Island in Alaska and Vancouver Island in Canada. Since amphipods are not found in these "new" feeding areas, the whales cannot be eating what they were 20 years ago.

Another possibility is that the population has outgrown the food supply and is a victim of its own success. Cooper, however, is not convinced. He says there is evidence that the currents passing through the Bering Strait have changed in the past decade, making the sediment less suitable for the phytoplankton that are the main food of amphipods. "There is also evidence that the overall productivity of the northern Bering Sea has declined over the past 10 to 20 years," Cooper says. Bodil Bluhm of the University of Alaska, Fairbanks, and her colleagues have found that amphipod populations in the northern Bering Sea have declined. "The food supply has diminished while the whale population has recovered over the past 50 years," Cooper says. "In my view, the stinky whales may be facing a food shortage." Reports last year that grey whales were arriving at their Mexico breeding grounds looking seriously undernourished have added to these concerns.

"A diminishing food supply over the past 50 years could be forcing the whales to follow a cetacean version of the Atkins diet"Losing blubber
So how would this account for the stink? The answer could be that it is a side effect of following a cetacean version of the Atkins diet. "Animals that suffer from food shortages alter their metabolism and produce ketones," says Geir Gabrielson, a toxicologist at the Norwegian Polar Institute in Tromsø. As with the Atkins diet in humans, this could be causing the whales to enter the state known as "ketosis", in which they burn fat for energy. In people, this causes bad breath. Perhaps the whales are undergoing something similar.

While a lack of their usual food looks the most likely culprit, the mystery of the stinky whales is far from solved. It could be that the whales are accumulating a marine biotoxin in their tissues, something the researchers plan to investigate in their next round of tests.

Meanwhile Rowles, along with researchers including Lorenzo Rojas Bracho of Mexico's National Institute of Ecology in Mexico City, are analysing respiratory gases collected from the blow of free-swimming whales during their winter breeding season in Baja California. By comparing the chemical profile of the gases in their breath with samples from stinky and normal whales in Russia, they hope to get an insight into what is happening to the whales' metabolism. "Gas chromatography is used to understand the metabolism of people who are on the Atkins diet," Rowles says. "We are trying to adapt that technique to whales to see if we can tease out what is going on." She and Rojas also plan to sample marine invertebrates from the feeding areas and analyse them for volatile organic compounds.

While researchers try to work out the true cost of smelling bad, the good news, says Bluhm, is that the whales seem to be flexible enough to seek other prey to survive short-term shortages. How they will fare if the problem continues remains to be seen.

07 May 2008
(c) New Scientist
Amitabh Avasthi

 

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