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On Bogoslof Island, a newly formed fur seal population draws researchers

Northern fur seals may have a long history in Alaska, but on Bogoslof Island, they're pretty new residents.

That's partially because the island itself is just a couple of hundred years old.

A team from the Alaska Fisheries Science Center has been studying fur seals on the active volcano in the Aleutian chain.

This summer, the team did several studies there including collecting data for the first population estimate in four years, as well as looking at their foraging behavior.

Researchers have long studied fur seals in the region, which were previously managed by the U.S Bureau of Commercial Fisheries, with data going back to the 1900s, according to Tom Gelatt from the science center's Alaska Ecosystem Program. They are one of the most studied populations of marine mammals in the world.

But on Bogoslof, zoologist Rolf Ream said the first pup was born in the 1980s. Since then, the population has taken off, the only place in Alaska where a fur seal population is increasing. Ream said the growth has been exponential.

The population estimate is based on a mark recapture study of pup production, Ream said.

"We're capturing the animals and putting a mark on them," Ream said.

Essentially, they mark them by clipping a small patch of hair with shears. Then they make observations to estimate how many pups were born this year, and use that to track the population over time. That's done every three to four years.

The newness of the population actually makes it ideal for some studies.

One project looks at disease prevalence. One question the researchers are looking at is how diseases are transferred between species. Bogoslof has both fur seals and Steller sea lions, so it's an opportunity to see what diseases appear in both, Gelatt said.

The Bogoslof work is also informed in part by studies done on the Pribilof Islands. Those are older, with more established fur seal populations -- and, notably, the population there is on the decline, although elsewhere in the world fur seal populations are healthy.

In part, researchers are looking at the newer island to try to better understand why the population on the Pribilofs is declining. (Despite the decline, it's still one of the most productive fur seal rookeries, the team noted.)

Gelatt said that much of the research done on Bogoslof is used to compare or contrast with the Pribilof studies. Gelatt said Bogoslof is a rich island, surrounded by deep water, and populated by thousands of birds.

Another recent study completed by the team showed that foraging trips for adult females feeding pups take longer on the Pribilof islands than on Bogoslof, although the Bogoslof trips have gotten longer as the population there has grown.

That gives researchers a sense not only of food availability, but also tells them about other components of a pups young life.

"The pups are much less vulnerable to other sources of mortality when moms are around," Gelatt said.

This story first appeared in The Bristol Bay Times/Dutch Harbor Fisherman and is republished here with permission.

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