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 user 2007-05-02 at 12:14:00 pm Views: 74
  • #18293

    Pacific whale decline ‘a mystery’
    Grey whales in the eastern Pacific appear to be in some trouble, with the cause far from clear, scientists say.
    with the conservation group Earthwatch found that whales are arriving
    in their breeding grounds off the Mexican coast malnourished.The same
    thing happened just after the 1997/8 El Nino event, which warmed the
    waters and depleted food stocks.Scientists are not sure whether the
    current decline is climate related or part of a natural predator-prey
    cycle.”We’re not really sure what is going on now,” said William
    Megill, a member of the Earthwatch team who also holds posts at Bath
    University in the UK and the University of British Columbia in
    Canada.”We certainly saw in Mexico this winter a very large number of
    starving whales,” he told the BBC News website. “There is currently an
    El Nino building, and this is a worry.”

    No fat
    There are
    thought to be between 15,000 and 18,000 grey whales in the eastern
    Pacific, a population that has been in generally good health since
    pulling back from the brink of extinction when hunting stopped in the

    Numbers may be higher now than before the hunting era.
    It may be a lot more serious than just grey whales – they may just be the early warning sign of changes for the whole Pacific,
    William Megill

    contrast, the other population, on the western side of the Pacific near
    Russia, has been in trouble for many years owing to a combination of
    hunting and, latterly, oil and gas exploration. It may now number as
    few as 120 individuals.On the eastern side, whales migrate between
    their summer feeding grounds to the north, which stretch from the
    waters near Seattle and Vancouver to the Arctic Bering Sea, and their
    winter breeding home along Mexico’s Baja peninsula.This is one of the
    longest migrations of any marine mammal; and at the end of it, in the
    last few years, Dr Megill’s team has found the animals arriving thin
    and exhausted.”The animals are starving, their fat has just gone, and
    there’s not a lot of breeding going on,” he related.”They seem to spend
    their time looking around for food when they should be breeding.”

    Going down
    cause of this change is not clear. A link with climatic conditions
    makes sense; warmer waters hold less oxygen, they become less
    productive, resulting in less of the tiny crustaceans which are the
    grey whales’ favoured food.

    This is thought to have caused the slump which followed the 1997/8 El Nino event.
    suggestion, from Dr Justin Cooke, who works with the World Conservation
    Union (IUCN) on cetacean issues, is that the greys have just become too
    plentiful.”No whale population can expand indefinitely,” he said, “and
    these whales seem to have exceeded their historical level so it would
    be surprising if they continued increasing – they’re due for a
    slump.”When whale numbers were lower there was enough to go round in
    poor years, but now numbers are higher and so there’s only enough to go
    round in good years.”William Megill acknowledges that the population
    could have become unsustainably high.”Around the year 2000, colleagues
    looked for mysids (tiny crustaceans) in kelp beds off the Canadian
    coast, and they found lots of them,” he said.”The last two years, we’ve
    stuck cameras down there and seen nothing.”It could just be the whales
    ate them all, and what we’re seeing is the same thing that happens to
    wolf and lynx populations when they eat too much of their prey.”But he
    is concerned that other factors may be involved too, in particular the
    slow rise in the average temperature of the oceans.The deepening annual
    Arctic melt, too, would also deprive the whales of a rich source of
    food, which accumulates along the edge of the pack ice.”I’m looking at
    it and thinking, ‘I’m a bit worried about it’,” he said, “and what we
    need to know is what’s going on quickly so we can get proper management
    plans in place.”It may be a lot more serious than just grey whales -
    they may just be the early warning sign of changes for the whole
    Pacific, and we urgently need to know what’s going on.”