Sea Lion Numbers Up: Arctic Science Journeys Radio

Radio Script
2002

Biologists have counted more adult and juvenile Steller sea lions across Western Alaska rookeries and haul-outs for the first time in 20 years. (Courtesy NMFS.)

Sea Lion Numbers Up
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INTRO: Steller sea lion populations in Western Alaska have declined steadily during the last 30 years. So few sea lions remain there today that federal officials have listed them as an endangered species. But this summer's count of sea lions along the state's coast has found cause for some optimism. Doug Schneider has more, in this week's Arctic Science Journeys Radio.

STORY: Federal biologists, using aerial photography, ships, and just plain walking the rocky, remote beaches from Prince William Sound west through the Aleutian Islands—where Steller sea lions breed and haul out—found a glimmer of hope in the nearly 30-year-long decline of the marine mammal. Biologists say that, overall, Steller sea lion numbers in Western Alaska grew by a modest 5.5 percent over the past two years. John Sease is a marine mammal biologist with the National Marine Fisheries Service in Seattle, Washington. He says the increase is a hopeful sign that sea lions, as well as the region's marine ecosystem, may be recovering.

SEASE: "This is the first time in roughly 25 years of systematic surveys through this region that we have actually seen an increase from one survey to the next. There has been a roughly 5 percent per year decline for the last ten years anyway, and it was much steeper before that. Just to have an increase of 5 percent, especially over a fairly wide geographic region, is certainly encouraging."

Steller sea lions (Eumetopias jubatus) live in the North Pacific Ocean and consist of two distinct populations separated at 144° W longitude (near Cape Suckling, just east of Prince William Sound, Alaska). The National Marine Fisheries Service listed the Steller sea lion as threatened range-wide under the Endangered Species Act in April 1990. The decline has continued for the western population in Alaska, which was declared endangered in 1997. The eastern population remains listed as threatened. (Courtesy NMFS.) Click image to see larger version.

Biologists survey Alaska sea lion populations every two years. Steller numbers in Southeast Alaska have remained stable, growing at about 1 percent each year. But it's sea lion numbers in western Alaska that worry scientists most. There, biologists surveyed 84 rookeries and haul-outs across nearly 2,500 miles of coast. In actual numbers, biologists counted 19,300 adult and juvenile sea lions in the region, or about 1,000 more animals than they did two years ago.

Although the count is up slightly, Sease says the actual number of adults and juveniles might be higher, since not all sea lions are on their haul-outs at any given time. And he says, researchers and fishermen have reported seeing more sea lions than usual around places such as Kodiak Island.

SEASE: "What we have seen just during the last few years while visiting haul-outs across Alaska during our regular work, it seems like we're seeing more juveniles. That's just a gut feeling. It's nothing quantitative. But if you combine that with what fishermen who are out on the water all the time are seeing, it seems like things are changing to them."

But it's not all good news for Steller sea lions. While overall counts in Western Alaska are up, Sease says that sea lions on haul-outs near the end of the Aleutian Island chain actually declined by about 24 percent during the past two years, and 75 percent since 1991.

SEASE: "So from Buldir Island westward, or maybe even from Amchitka westward. So the western third of the Aleutians is still going down."

Also of concern are Steller sea lion pups, long thought to be a critical part of the species decline. Their numbers continued their decades-long downward slide. Sease says pup counts on 24 western Alaska rookeries over the past two years have showed a nearly 8 percent decline.

SEASE: "You have to have numerous surveys over a period of many years before you can really detect a change that's real—that mathematically can be proven as a real change. In common-sense terms, it means that one data point reversing a trend doesn't mean that the trend has in fact changed. It could be just a high count for whatever reason."

Sease points out that even with this year's increase, the total number of sea lions is still far below what it was in past years. In the 1960s, before the decline is believed to have begun, Steller sea lion numbers were estimated at more than 200,000 in Western Alaska.

Steller sea lion declines at Ugamak Island in Alaska's Aleutian Island chain. (Courtesy NMFS.) Click image to see larger version.

SEASE: "At those same sites we are still below where we were in 1998. We're still below where we were four years ago, and we are way below where we were ten years ago."

This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences. I'm Doug Schneider.

Audio version and related websites (above right)

Thanks to the following individual for help preparing this script:

John Sease
National Marine Fisheries Service
National Marine Mammal Lab
WASC Route: F/AKC3
Seattle, Washington 98115-6349
Phone: 206-526-4024
Email: John.Sease@noaa.gov

Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks. The shortcut to our ASJ news home page is www.asjnews.org.

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