What’s the deal on the number of seals?

U.S. and Russia to begin Bering Sea aerial survey to determine populations

Scientists from Russia and the United States will use high-resolution photography and thermal sensors to count ice seals in the Bering Sea. Among them are spotted seals, a species the National Oceanic and Atmospheric Administration rejected for listing as a threatened species three years ago. Enlarge photo

NOAA/AP file

Scientists from Russia and the United States will use high-resolution photography and thermal sensors to count ice seals in the Bering Sea. Among them are spotted seals, a species the National Oceanic and Atmospheric Administration rejected for listing as a threatened species three years ago.

ANCHORAGE, Alaska – A team of researchers 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 from the United States and Russia will count ringed and bearded seals, which the National Oceanic and Atmospheric Administration has recommended for listing as threatened species because of climate warming.

The agency is conducting a status review of a third ice-dependent species, the ribbon seal, and will also count spotted seals, a species it rejected for listing three years ago.

Getting an accurate count has been challenging because of the expense of conducting research in a remote location, the difficulty of counting species that spend time on both water and ice, and the danger to scientists flying in small airplanes.

Scientists hope to obtain significant results beginning this week by combining thermal imaging with high-resolution photography.

“The most novel thing about the survey is the pairing of two devices that have already been used to survey other marine mammals,” said Peter Boveng of the National Marine Mammal Laboratory in Seattle, in the announcement of the study.

The two aircraft picked for the project will fly at 1,000 feet, which is too high for the human eye to distinguish the seals. The thermal sensors, Boveng said, will locate the animals. The high-resolution cameras will take images to be analyzed in a lab.

“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,” Boveng said. “High-resolution digital photos are good for species identification, but very labor intensive for detecting and counting seals.”

He said putting the two technologies together creates a more efficient system in which the thermal camera finds the seals and the photo camera allows identification of species.

The survey will be conducted into May, and plans call for flying nearly 19,000 nautical miles over U.S. waters and 11,000 nautical miles over Russian waters, making it the largest-ever seal survey in the Bering Sea.

The first flights will begin from Nome. Five- to seven-hour survey flights also will originate in Bethel and Dillingham in southwest Alaska and St. Paul Island, the largest of the Pribilof Islands 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 because of projected loss of sea ice.

For ringed seals, the proposal also cited the threat of reduced snow cover because of climate warming. A final decision was due last 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. They give birth to young in snow-covered lairs on sea ice.

Bearded seals give birth and raise pups on drifting pack ice over shallow water where prey such as crabs is abundant. When females give birth, they need ice to last long enough in the spring and early summer to successfully reproduce and then molt.

NOAA Fisheries in December 2008 rejected a threatened species listing for ribbon seals. The decision was based on an interpretation of climate models that concluded that annual ice would continue to form for ribbon seals each winter during birthing and molting. The agency in December, however, announced it was taking another look because new information had become available.

The agency in October 2009 rejected listing spotted seals in waters off Alaska and the decision was not challenged.

NOAA/AP
This map shows the planned survey track lines for a joint U.S.-Russia ice seal survey to be conducted through May. Enlarge photo

NOAA/AP This map shows the planned survey track lines for a joint U.S.-Russia ice seal survey to be conducted through May.

Ribbon seals, such as this one captured on film in 2008 by NOAA during an aerial survey, have not been recommended for listing as a threatened species, but will be counted during the ongoing survey. Enlarge photo

NOAA/AP file

Ribbon seals, such as this one captured on film in 2008 by NOAA during an aerial survey, have not been recommended for listing as a threatened species, but will be counted during the ongoing survey.