Tracking a sea lion's life

Southeast Steller sea lion numbers doing well, Western Alaska population decline

Posted: Sunday, September 07, 2008

On a blustery July day in Glacier Bay, about 50 Steller sea lions were hauled out on the rocks at South Marble Island. Amid the caterwauling and bellowing animals jockeying for position rested one placid male, a letter and a number on his left side, H 465.

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Another marked male rested nearby; he is known as "= 465."

According to marine mammal biologist Lauri Jemison of the Alaska Department of Fish and Game, these are "northern boys," young sea lions that favor northern Southeast Alaska. It's a coincidence that both share the same number.

Both sea lions are Juneau locals - more or less - Benjamin Island regulars. Benjamin Island, about three miles north of Eagle Beach, is one of the major sea lion haulouts in Lynn Canal.

Steller sea lions are declining in Western Alaska, but doing well in Southeast Alaska. Over the past decade, biologists have marked about 3,600 animals with identifying numbers. To learn how animals live and move about, it's crucial to be able to identify who is who.

As the animals are re-sighted over the years, biologists get a picture of their movements and their fidelity to certain haulouts, rookeries, and feeding areas. They can also learn how long sea lion pups stay with their mothers, how long they depend on their mothers for nursing, and how often females reproduce. It's also important to learn if sea lions are moving between Western Alaska and Southeast Alaska, since animals in these two areas are considered to be separate populations or stocks.

Biologist Lauri Jemison provided the back story for sea lion H 465.

H 465 was born in June 2005 at the Hazy Islands, where Chatham Strait meets the Gulf of Alaska. The Hazy Islands are one of the four major sea lion rookeries in Southeast Alaska.

In the fall of 2005, the young pup accompanied his mother about 200 miles due north, up the long fjord of Chatham Strait, to Benjamin Island. He spent the winter there and in the spring of 2006 he swam north another 45 miles to Gran Point, near the Katzehin River just south of Haines. Later that summer the one-year-old sea lion swam 100 miles south to Sail Island north of Petersburg, at the south end of Stephens Passage. Sail Island and the nearby Brothers Islands, sitting where Stephens Passage meets Frederick Sound, are well-used sea lion haulouts.

H 465 repeated this pattern in 2007 - he was in the north in the spring at Gran Point, and in June he was back at the southern end of Stephens Passage around the Brothers Island for the summer. In the summer of 2008, the 3-year-old was found in Glacier Bay, a 100 mile-swim to the northwest.

Lauri Jemison and her colleagues are continuing their work studying the population dynamics of Steller sea lions in Southeast. They are also working to monitor and address the problem of sea lion entanglements in trash and fishing gear. Future sightings will reveal more about the movements and life of this and other Steller sea lions.

• Riley Woodford is a writer with the Alaska Department of Fish and Game, Division of Wildlife Conservation. He is the editor of Alaska Fish and Wildlife News, available online at http://www.wildlifenews.alaska.gov/

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