(AP) -- A partial federal assessment of Pacific walruses estimates their minimum population at just 15,164 but says the count likely missed a number of animals.
The estimate released Thursday only represents animals counted in about half of walrus habitats in the Bering and Chukchi seas and does not account for animals that were in water rather than on ice.
The count was done by U.S. Fish and Wildlife Service in response to a court deadline requiring the agency to identify marine mammal stocks most affected by interactions with commercial fishing.
"We're still working on the final population estimate," said Suzann Speckman, a wildlife biologist with the agency.
A 1990 aerial survey estimated the walrus population at 201,039 in the region.
Pacific walruses are found mainly in the two seas off the west coast of Alaska in waters shared with Russia. Walruses occasionally move into the Beaufort Sea off northern Alaska and the East Siberian Sea on the Russian side.
Fish and Wildlife Service officials have been working since 2006 on a full walrus estimate with their Russian counterparts using thermal imaging. The latest target date for release of those numbers is January, Speckman said.
Brendan Cummings, a spokeseman for the Center for Biological Diversity, said the group was frustrated with the delay. The center has petitioned to list walruses as endangered because of the impact of global warming on Arctic sea ice.
In some ways, however, the number of remaining walruses is not important, he said.
"You don't need to know if there are 500 passenger or 1,000 passengers on the Titanic," he said. "When it hits an iceberg, they're all endangered."
Walruses dive from ice over the shallow outer continental shelf to feed on clams and other benthic creatures. Walruses cannot swim indefinitely, and females and young animals traditionally use ice as a moving diving platform to shift hunting areas.
Cummings said the changing conditions in the Arctic are being minimized by Fish and Wildlife Service in reports and decisions on oil and gas leasing.
"The management side of Fish and Wildlife has its head in the sand pretending everything is fine with these species when clearly it is not," he said.
Federal law requires updated stock assessments every year for imperiled marine mammals and every three years for other species.
Wildlife biologist Doug Burn said agency officials had hoped to have a firm walrus population count by now but experienced problems with the thermal imaging methodology.
A method that counts walruses using body heat was tested near St. Lawrence Island during a relatively warm winter but did not prove reliable during a colder winter in 2006, Burn said.
"We realized we were missing a lot of walrus groups," he said.
It took a year to develop and use a new technique, Burn said.
The biologists cautioned against relying too heavily on the partial count of 15,164 walruses.
Ice types, bottom depth, prey abundance and other factors will figure into a final count, they said.
Counting marine mammals in the Arctic is notoriously difficult. Biologists rely on aircraft that must fly in extreme cold, often at low altitudes in low light or darkness far from airports that could provide safe landings if the aircraft gets into trouble.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Fish tale: New study evaluates antibiotic content in farm-raised fish