An aerial survey from the National Oceanic and Atmospheric Administration shows an adult male ribbon seal in the Bering Sea.
ANCHORAGE, Alaska — U.S. and Russian researchers this week will begin flights over Bering Sea ice to answer a basic question about four of the region's most important species: How many ice-dependent seals are out there?
Scientists will count ringed and bearded seals, which the National Oceanic and Atmospheric Administration has recommended for listing as threatened species due to climate warming.
The agency is reviewing a third ice-dependent species, the ribbon seal, and will count spotted seals, a species it rejected for listing three years ago.
Getting an accurate count has been challenging due to the expense of conducting research in a remote location, the danger to scientists flying in small airplanes and the difficulty of counting species that spend time on both water and ice.
Scientists will combine thermal imaging with high-resolution photography.
"Thermal or infrared cameras are good at detecting seals on ice, which are very warm relative to their surroundings, but not good at revealing the species of seals," said Peter Boveng of the National Marine Mammal Laboratory in Seattle. "High-resolution digital photos are good for species identification but very labor-intensive for detecting and counting seals."
The survey will be conducted into May and is expected to be the largest-ever seal survey in the Bering Sea.
The Center for Biological Diversity petitioned to list ringed and bearded seals in 2008 and eventually sued to force a decision.
NOAA Fisheries in 2010 proposed listing ringed seals in the Arctic Basin and the North Atlantic and two populations of bearded seals in the Pacific Ocean as threatened species because of projected loss of sea ice.
A final decision was due in December, but the agency announced a six-month delay.
Ringed seals are the main prey of polar bears, which were listed as threatened by the U.S. Fish and Wildlife Service in 2008. They are the smallest of the ice seals but the only ones that can live in completely ice-covered waters.