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15:12
20 February 2005
NewScientist.com news service
John Pickrell, Washington DC
A new genetic study has revealed that the Antarctic minke
whale may have been much more abundant before whaling
began than previous estimates suggest.
The DNA survey of whale meat purchased in Japanese grocery
stores reveals that the species has the most genetically
diverse population of any whale, indicating the species
historically had a population of between 500,000 and one
million individuals.
The finding is significant because Japanese delegates
to the International Whaling Commission (IWC) have previously
argued that recent surges in minke whale numbers are unprecedented.
Japan claims that the current population of around 761,000
Antarctic minkes (Balaenoptera bonaerensis) is so abnormally
abundant that it is hindering the recovery of other large
endangered species, such as the blue whale. The data has
been used to support calls for the resumption of commercial
whaling of Antarctic minkes.
In 2004, Japan asked the IWC to allow it to resume a
catch of nearly 3000 Antarctic minke whales annually,
six times the amount it currently catches under a scheme
for scientific research.
Old whaling figures
Most estimates of historic whale population size have
been extrapolated from old whaling figures, but this method
is often very inaccurate, argues marine biologist Steve
Palumbi of Stanford University's Hopkins Marine Station
in California, US.
Palumbi and colleagues used DNA samples in 2003 to estimate
that humpback whales could have numbered 1.5 million prior
to the onset of commercial whaling in the 1800s. That
number dwarfs the figure of 100,000 previously accepted
by the IWC and based on 19th century whaling records.
Humpback whales currently number 20,000.
Genetic diversity indicates the past abundance of a species
because large populations tend to accumulate it through
breeding, while small populations lose it through inbreeding.
Palumbi used two different types of gene in the sampled
whale meat to derive his estimated pre-whaling population
estimate of between 500,000 and one million. He announced
his results at the American Association for the Advancement
of Science meeting in Washington, DC, US, on Sunday.
Pristine population
The new estimate is vastly greater than previous ones,
the most extreme of which placed the historic population
size of Antarctic minke whales as low as 20,000, says
Palumbi.
Japan's claim that these whales were originally much
rarer than now is almost certainly not true, Palumbi told
New Scientist, and "there is no evidence whatsoever
that their population growth is inhibiting populations
of other whales in Antarctica".
"We have often underestimated the pristine population
size of marine species" agrees oceanographer Craig
Smith from the University of Hawaii in Manoa. "Whaling
figures can provide very inaccurate estimates."
The genetic data also revealed that the Antarctic minke
whale population may be the oldest surviving whale population
on Earth. Palumbi was able to extrapolate its origin as
far back as single minke whale - a "mitochondrial
Eve" - at least one million years old.
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