Whale Populations in NA Were Once Far Larger Than Previously Estimated

[Submariner]

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Scientists have vastly underestimated the number of humpbacks and other
great whales that inhabited the North Atlantic Ocean before the advent
of whaling, according to geneticists from Stanford and Harvard
Universities. The claims, published in the journal Science, could, say
the study's authors "represent a major setback for countries that
advocate lifting a 17-year moratorium on commercial whaling established
by the … International Whaling Commission."

The authors note that the IWC and other bodies estimate historic whale
population levels by extrapolating from whaling logbooks – which, they
point out, "may be incomplete, intentionally underreported or fail to
consider hunting loss."

To assess the accuracy of historic whaling records, the study's authors
– Joe Roman of Harvard University, and Stephen Palumbi of Stanford
University's Hopkins Marine Station – used population genetics to
assess the initial population sizes of fin, humpback, and minke whales
in the North Atlantic: "the first attempt to use genetics rather than
whaling records to confirm the number of whales that used to exist,"
according to Palumbi.

"The genetics of populations has within it information about the past,"
Palumbi observed. "If you can read the amount of genetic variation -
the difference in DNA from one individual whale to another - and
calibrate that, then you can estimate the historic size of the
population … A small population tends to weed out all of its genetic
differences through inbreeding. A large population, by contrast, should
have a lot more genetic variation. Our study shows that humpback whales
today actually have about 10 times more genetic variation than would be
expected from the whaling logbook estimates. That tells us that,
sometime in the past, the population of humpbacks was pretty big - and
in fact our calculation for the North Atlantic suggests that the
historic size of that population was about 240,000 animals." That
figure is more than ten times the accepted historical estimate for
humpbacks in the North Atlantic.

An analysis of fin whale DNA yielded similar results. According to
historic whaling records, about 40,000 fin whales once inhabited the
North Atlantic. Current IWC estimates place today's fin whale
population at 56,000, which would be an all-time high. But a genetic
comparison of 235 fin whales by Roman and Palumbi revealed that the
actual pre-whaling population was probably about 360,000 - again,
roughly ten times higher than the IWC's historical estimate. The
researchers estimated the pre-hunting population of minke whales in the
North Atlantic at approximately 265,000 – roughly twice the number
believed to exist today, but closer to previously-assumed estimates of
historic numbers.

"Somehow we have to reconcile those numbers," Palumbi added. "That's
going to require going back and looking at the whaling records. Are
they complete? Have there ever been large hunts of whales that weren't
recorded? These are things that we have to find out."

Other observers noted the potential significance of the Science paper's
findings. "One of the few collective actions of mankind was to save the
great whales from extinction through a worldwide ban on commercial
whaling," commented Dr. Boris Worm, a researcher with the Institute of
Marine Sciences at Kiel University in Germany. "This new paper … shows
us that, despite recent population increases, we are still far away
from our goal of allowing whales to recover fully from relentless
exploitation."

The loss of more than 800,000 humpback, fin and minke whales in the
North Atlantic is likely to have altered the entire web of life in that
ocean, added James Estes, a research scientist with the U.S. Geological
Survey and adjunct professor of biology at the University of
California-Santa Cruz: "Clearly, the disappearance of the great whales
was not an isolated event." Not only are baleen whales major consumers
of krill and small fish, he explained, but when they die, their massive
carcasses sink to the bottom and provide vital nutrition for a wide
variety of creatures on the sea floor. For example, an adult humpback
can reach 50 feet in length and weigh up to 40 tons. Multiply that by
240,000 whales, he said, and the impact of the loss becomes apparent.

"Sharks and killer whales are known to prey upon humpback whales, and
their demise likely had a big effect on those predators as well," Estes
noted. "So the implications of the Roman-Palumbi study for ocean
conservation are startling. It could entirely redefine our recovery
criteria for whales."

Source: Roman, J., and S.R. Palumbi. 2003. Whales before whaling in the
North Atlantic. Science 301: 508-510.

Contact: Joe Roman. E-mail: [e-mail]

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