Posted on 27-7-2003
Whales
May Have Been More Plentiful
By Guy Gugliotta, Washington Post, 25 July 2003
Scientists may have profoundly underestimated
the number of whales that once lived in the North Atlantic Ocean,
a controversial finding that could have critical implications
for the future of whaling and whale conservation, a new genetic
study concludes.
The gulf between the new estimates
and those from existing historical-statistical studies is so
vast -- a difference of several hundred thousand animals --
that it has already provoked a spirited debate over scientists'
techniques in gathering and analyzing the data.
"We're suggesting that the oceans
can support these populations in the long term, and in fact
did," said geneticist Joe Roman, a Harvard University graduate
student and co-author of the new study with Stanford biologist
Stephen R. Palumbi. "There are all kinds of different views
on this, and we knew it was going to be controversial, but this
is what the data show."
Roman and Palumbi analyzed DNA from
three species of North Atlantic whales and found the genetic
variation to be unexpectedly high in all cases -- a result indicating
that before commercial whaling began in the 17th and 18th centuries
there was a much larger pool of animals than historical records
suggest.
In fact, the authors report today in
the journal Science, their analysis showed that the pre-whaling,
or "historic," population of humpback whales in the
North Atlantic was 240,000, 12 times as many as the current
historical-statistical estimate of 20,000. There are about 10,000
now.
Roman and Palumbi also estimated the
historic population of fin whales at 360,000, nine times more
than historical-statistical estimates of 40,000, and the population
of minke whales at 265,000, as against statistical estimates
of approximately 100,000.
The findings could play an important
role in decisions of the International Whaling Commission, the
51-nation convention that imposed an international moratorium
on whaling in 1985 to allow stocks to rebuild after the decimation
of the 19th and 20th centuries.
The commission has agreed that whaling
should not be allowed until stocks reach at least 54 percent
of historic levels. Under this stipulation, the current North
Atlantic humpback population is about 50 percent of historical-statistical
estimates, while fins, at 56,000 and minkes at 149,000 have
already exceeded the threshold.
But under the new genetics-based estimates,
only the minkes are close to 54 percent. "One of the things
that the data tell us is that we have a long way to go for recovery,"
Roman said in a telephone interview. "Things were vastly
different in the relatively recent past. How do we get to that
restoration? I don't know."
Commission Secretary Nicola Grandy
did not comment on the new study but noted that "a majority
of our members currently don't want to see a return to commercial
whaling." And if they did, Grandy said in an interview
from the commission's Cambridge, England, headquarters, whaling
would be strictly confined to particular species and locations
.
The commission has based its estimates
of historic populations on statistical analyses derived from
whaling records and logbooks. Before commercial whaling began
in the 1600s, humans had no effective way of hunting whales
on the high seas, and even during the "Moby Dick"
era in the mid-19th century, wooden ships could not handle anything
bigger than a 50-ton humpback.
"Right whales were the favorites,
because they were 'right' -- they were slow, coastal and they
floated after you killed them," said mathematician and
fisheries specialist Doug Butterworth, of South Africa's University
of Cape Town.
"Fin and blue whales were big,
fast and would pull you right to the bottom if you killed them,"
he said. Fin whales weigh 70 tons, while blue whales, which
can weigh 120 tons, are the biggest animals that ever lived.
Fin whale hunting began only with the advent of steam-driven
whalers in the 1880s.
Estimating historic whale populations
in the traditional way is "simple," said Butterworth,
a member of the commission's Scientific Committee. "You
figure how many whales there are, and add to that how many were
caught." The pre-commercial census would be even lower
if it accounted for natural reproduction during the whaling
years.
The discrepancy between traditional
estimates and those in the new study is so huge that it defies
easy reconciliation, added fisheries biologist Timothy D. Smith,
of the Commerce Department's Northeast Fisheries Science Center
in Woods Hole, Mass. "If there was a secret population
somewhere, we don't know where it was," said Smith, another
Scientific Committee member. "These guys [whaling captains]
went everywhere."
Roman and Palumbi did their analysis
by studying the rate of genetic variation in the mitochondrial
DNA, which is inherited only from the mother, of the three whale
species, and found a rate of mutation much higher than would
be expected from the historical-statistical estimates.
The authors wrote that "whaling
logbooks may be incomplete, intentionally underreported or fail
to consider whales that were struck and lost," a judgment
Smith called "facile" and "disturbing."
"If they'd come up with numbers
that said twice as many, then maybe we'd start thinking about
our methods," Butterworth added. "But when you come
up with five-to-10 times as many, then maybe they're the ones
who ought to take another look."
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