Pacific gray whale 'declining'
Gray whales help to provide food for other sealife
Also In The News
|
Cooking Vinyl, September 17th. |  |
Tuesday, 11, Sep 2007 10:34
Numbers of gray whales in the Pacific Ocean have reduced dramatically due to the climate's impact on food supply, genetic tests have shown.
Researchers at Stanford University and the University of Washington believe that the whales were once three to five times as plentiful as they are now.
More than 22,000 gray whales exist compared to the estimated figure of 96,000 before whaling began.
It had been thought that a dip in whale numbers between 1999 and 2001 was due to the animal reaching its historical ecological capacity.
But writing in the journal Proceedings of the National Academy of Science, the researchers argue that the whales may be starving due to a reduced food supply from changing climatic conditions in their Arctic feeding grounds.
They reached their conclusion after studying DNA samples from 42 gray whales.
As genetic diversity changes slowly over time, DNA variation is a good indicator of past population numbers.
"Our survey uncovers too much variation for a population of 22,000," said Professor Steve Palumbi from Stanford's Hopkins Marine Station.
"The overabundance of genetic variation suggests a much larger population in past centuries."
Reduced numbers of gray whales will also have an impact on other species in the Pacific Ocean, the researchers add.
The whales dig troughs in the seabed for food, sending food to the surface which other animals live on. The feeding plumes of gray whales also provide foraging grounds for Arctic seabirds.
"Despite our best efforts these genetic results suggest gray whales have not fully recovered from whaling. They might be telling us that whales now face a new threat - from changes to the oceans that are limiting their recovery," said Professor Palumbi.
"Decades ago, whales were the first creatures to tell us that we were overfishing the oceans. Maybe now they trying to tell us the oceans are in deeper trouble."