Web posted Sunday, February 18, 2007

Fur seals' disappearing act a mystery for scientists

By Margaret Bauman
Alaska Journal of Commerce

  Fur seals and pups sit on a beach on St. Paul Island In this 2006 photo released by the National Oceanic and Atmospheric Administration. Federal biologists reported Feb. 2 that America's northern fur seal pup population has experienced a marked decline in this decade. AP PHOTO/Rod Towell/NOAA    
Federal fisheries officials are reporting a 9 percent decrease in the number of northern fur seal pups born between 2004 and 2006 in the Pribilof Islands, but have no clear answers on why this is happening.

“We have seen a significant decline in the abundance of fur seals on the Pribilof Islands starting about 1998, and we have not been able to identify the factors responsible,” said Doug DeMaster, director of the Alaska Fisheries Science Center within the National Oceanic and Atmospheric Administration.

NOAA announced its findings Feb. 2.

The news came as no surprise to Larry Merculieff, deputy director of the Alaska Native Science Commission and a co-founder of the International Bering Sea Forum, a grassroots effort to look at the Bering Sea ecosystem and to advocate for scientific research.

“The people in the Pribilofs have been noticing these changes for some time,” said Merculieff, a former city manager of St. Paul.

“We don't believe there is a single cause, but we need to reduce human impact on fur seal food,” he said.

Merculieff particularly takes issue with arguments that the Bering Sea fisheries are the best-managed fisheries in the United States. “It doesn't account for management and research of one-half of the entire Bering Sea ecosystem, the Russian side,” he said. “There is no management coordination on a high level. How can you manage half of an ecosystem?”

Fur seals aren't the only species in trouble, he said. “There are over 20 other major species declining in the Bering Sea, and they are all connected,” he said.

Merculieff said he was out in the Pribilofs last year and went to five rookeries at the end of June. “Where we might see 2,000 to 4,000 females at that time, I actually counted only five.”

For the first time in the history of the islands, subsistence hunters had to go to three different rookeries to get their subsistence quota of 50 fur seals, he said. This has not occurred since the catastrophic decline of fur seals in the early 1900s, which was due to the high-seas killing of the seals, he said.

For about a decade, beginning in the late 1950s, there was government-authorized culling of female fur seals over the protests of residents of the Pribilofs. A second population decline occurred in the late 1970s. By about 1977, people started noticing anomalies in the fur seal population again, Merculieff said. In the 1980s, the government acknowledged there was a problem, and declared fur seals depleted in 1996, but nothing really changed in terms of management or funding for research, he said.

“After that, people predicted a third series of declines, saying it was probably food and ecosystem-related, and that those issues had not been resolved. People began to note on St. George and St. Paul that the fur seals were continuing to decline, up until temporarily stabilizing,” he said.

Researchers say the complexity of ecosystem interactions, and limitations of data and models, make it difficult to determine how fishery harvests may have influenced this population. Other factors that may have contributed to past or current declines of northern fur seals include entanglement in marine debris, parasites and disease, pollutants, general nutrition and predation, researchers said.

The main components of the northern fur seal's diet include fish such as herring, anchovy, pollock and capelin, as well as squid.

Northern fur seals are considered depleted under the Marine Mammal Protection Act. The pup estimate decreased most sharply on St. Paul Island. St. George Island showed a small increase over 2004, though it still registered a decrease of 3 percent from the 2002 estimate, researchers said.

In contrast, the total number of adult males counted in the Pribilof Islands increased about 4 percent since 2005.

DeMaster said that NOAA has a very long scientific record of the population of northern fur seals in the Pribilofs. “Adult male counts began in 1909, and pup counts were initiated in 1912,” DeMaster said. “At that time, the northern fur seal population was rebounding at a healthy 8 percent per year, following the cessation of extensive pelagic (open seas) sealing.”

The northern fur seal population rose steadily from the end of unregulated ocean and on-land sealing into the 1950s, when scientists estimated the population at about 2 million. A harvest of adult females from 1956 to 1968 reduced the population through the 1970s. The total Pribilof population size stabilized briefly from about 1980 through the mid-1990s, but has since declined.

The Pribilof Islands are the main breeding and resting areas for northern fur seals, but they also claim other, much smaller breeding areas on Bogoslof, San Miguel and South Farallon islands in the United States and in foreign waters on the Russian islands of Kurile, Commander and Robben. Pribilof Island fur seals spend only the summer months foraging in the Bering Sea. The rest of the year they migrate south of the Aleutian Islands and forage in the ocean.

Citizens of the Pribilof Islands have assisted with population monitoring, behavioral research and untangling seals. Island residents working for the tribal governments on St. Paul and St. George now lead investigations of fur seal entanglement as members of the Alaska Marine Mammal Stranding Network, funded competitively through the national Prescott grant program.

Margaret Bauman can be reached at margie.bauman@alaskajournal.com.