Alaska Ecosystems Research Program
Resight Surveys for Branded Steller Sea Lions in Gulf of Alaska and Eastern Aleutian Islands
In order to estimate movement patterns, survival, and
other vital rates of Steller sea lions (Eumetopias jubatus), the
National Marine Mammal Laboratory (NMML) and Alaska Department of Fish
and Game have been marking pups with brands or flipper tags at rookeries
in the eastern Aleutian Islands, in the central and eastern Gulf of
Alaska, and in Southeast Alaska. During the last 2 weeks of May 2005,
ship-based surveys were conducted in the Gulf of Alaska and the eastern
Aleutian Islands to resight branded and tagged Steller sea lions.
Resights were conducted at 64 sea lion haulouts and
rookery sites in the eastern Aleutian Islands and western/central Gulf
of Alaska between 169° 15’ W (Samalga Island) and 155° 39.5’ W (Chirikof
Island) aboard the chartered fishing vessel Aleutian Mariner.
Fifty-eight branded sea lions were observed among a total of
approximately 6,146 nonpup sea lions seen at all sites. Most of the
branded sea lions observed were branded as pups at Ugamak Island
rookeries 2001 (n = 20) or 2003 (n = 28). Other sea lions branded as
pups that were observed included two from Marmot Island, one from
Sugarloaf Island, and two from Forrester/Lowrie Island. Additionally,
five sea lions that were initially dive-captured as yearlings or
juveniles were resighted.
A second resight cruise was conducted at 40 sea lion
haulouts and rookery sites in the Kodiak Archipelago and along the
Alaska and Kenai Peninsulas aboard the chartered vessel Waters.
Eighty-three branded sea lions were observed among a total of
approximately 2,590 nonpup sea lions seen at all sites. The majority of
branded sea lions observed in this area were branded as pups on Marmot
and Sugarloaf Islands in 2000 (n = 16), 2002 (n = 14), and 2004 (n =
40). Five branded animals from Southeast Alaska were also sighted,
including two each from Forrester and Hazy Islands and one from Graves
Rock. Two sea lions that were initially dive-captured as yearlings or
juveniles were resighted, and an 18-year-old female, "763," which was
branded on Marmot Island in 1988, was observed on Sugarloaf Island.
During these surveys, fecal samples were collected
for diet and genetic analysis. Additionally, the Aleutian Mariner
delivered field camp supplies and cabin building materials to Ugamak
Island for scientists doing land-based brand resights and behavioral
observations of Steller sea lions.
Steller Sea Lion Pup Survey
The Alaska Ecosystems Program conducted its annual
Steller sea lion pup survey cruise aboard the U.S. Fish and Wildlife
Service (USFWS) research vessel Tiglax in the eastern Aleutian
Islands through the central Gulf of Alaska from 20 June through 6 July
2005. Live pups (n = 3,395) and dead pups (n = 80) were counted at 12
rookeries and haulouts to monitor population trends. Pups were branded
at Ugamak (n = 200) and Seal Rocks (n = 80) rookeries for studies
estimating survival and other vital rates. In order to assess condition
and health status, morphometrics (weight, girth, length) and tissue
samples (blood, tissue, fecal) were collected from 50 randomly selected
pups at Akutan (Cape Morgan), Jude, and Chowiet Islands, and from 40
pups at Clubbing Rocks South. Four freshly-dead pups were collected from
Seal Rocks, a rookery with high pup mortality, for necropsies.
Additionally, 74 scats were collected for dietary analysis, and 73
previously branded and tagged sea lions were resighted.
Steller Sea Lion Field Camps
Scientists from the Alaska Ecosystem Program were
stationed on Marmot and Ugamak Islands beginning in late May and running
through July 2005. Steller sea lions breed and give birth at rookeries
on both islands, and the program has branded pups born there since 2000
(and in 1987-88 at Marmot). Scientists living on the island collect data
on Steller sea lion vital rates and dispersal (brand resights),
behavior, abundance, and attendance. Three scientists and a carpenter
were transferred by helicopter to Ugamak Island from Dutch Harbor
beginning in late May. Materials to build a cabin at Ugamak were
transferred by helicopter to the island from the Aleutian Mariner
on 30 May. The carpenter was transferred off Ugamak to the Tiglax
in late June during the pup survey cruise so that he could travel to
Marmot Island and begin building a cabin at the south end of the island
in early July. Cabin materials were delivered from Kodiak to the south
end of Marmot Island by amphibious vessel in May and were moved to the
top of the island by helicopter in early June when the four NMML
scientists arrived. For the first time, field camps at both the north
and south ends of Marmot Island were occupied, permitting simultaneous
and complete coverage of both rookery beaches (beaches 4 and 7).
By Tonya Zeppelin and Lowell Fritz
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AFSC Quarterly Research Reports April-June 2005
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