NOTES
FROM THE FIELD
Consortium Researchers recently wrapped up a successful summer
field season in the Aleutian Islands, Gulf of Alaska, Southeast
Alaska and British Columbia. The studies focused on killer
whale predation, Steller sea lion diets and the effects of
human disturbance on sea lions.
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Scat Collection and Dietary Analysis for the Eastern Stock of Steller
Sea Lions
Monitoring diet is one of the most important research activities
needed to assess the decline and recovery of Steller sea lions.
Monitoring diet is one of the most important research
activities needed to assess the decline and recovery of Steller
sea lions. Since 1993, Consortium Researchers have been collaborating
with the Alaska Department of Fish and Game, and more recently Fisheries
and Oceans Canada, to monitor the diets of the eastern stock of
sea lions. The work continued this summer with the successful completion
of three research cruises between June and August.
Researchers visited most of the major rookeries and haulouts, and
managed to collect approximately 2,000 scats.
Cleaning and identification of the bones contained
within the scats is underway. The primary goal is to determine
how the diet of sea lions in the growing southeast Alaska and
British Columbia population differs from those in the Gulf of
Alaska and Aleutian Islands. It also provides insight into the
diets of sea lions relative to the availability of prey.
Assessing the Short-term Effects of Human Disturbance
on Steller Sea Lion Behaviour.
One of the major questions perplexing researchers and permitting
authorities is whether or not people are contributing to the population
decline by disturbing Steller sea lions. Major disturbances can
occur when people approach rookeries and haulouts. While most
people feel that they are not having a major impact, this assessment
has never been properly tested.
 Between
May and August, two teams of researchers set out to document the
short-term effects of human disturbance on Steller sea lion behaviour
in Southeast Alaska and British Columbia. Laura Kucey (MSc candidate)
and her assistants conducted counts and behavioural observations
at 6 sites. Sea lions were observed for 1-2 weeks prior to being
disturbed, and for another 1-2 weeks following the disturbance.
Counts and group scans were conducted every twenty minutes, twelve
hours a day, to document the sea lion activities. An additional
study documented individual animals arriving on shore to determine
normal patterns of interactions and disturbance associated with
the movement of animals on land.
The study was successful and has yielded a great deal of data.
Analyses will now be performed to compare populations and activity
levels within and between each location. Results of this study
will contribute to our understanding of the effects of human disturbance
on Steller sea lion.
Killer Whale Predation
 Killer
whales could be the single most important factor preventing the
recovery of Steller sea lions in the Gulf of Alaska and Aleutian
Islands. Unfortunately, little is known about killer whales west
of the Prince William Sound/Kenai Fjords. The killer whale research
program led by Craig Matkin and Lance Barrett Lennard completed
their second field season, and yielded new information and some
surprises.
Some of the killer whales seen near Kodiak were
previously seen further east. However, the whales seen west of
Kodiak in the eastern Aleutians appear to be separate. Both resident
(fish eating) and transient (marine mammal eating) ecotypes have
now been seen in the Aleutians, but most of them (over 500 identified
to date) have been the fish-eating residents.
Last year, fewer than 10% of the whales seen were
genetically typed as marine mammal eating transients. However,
this spring over 80 suspected transient killer whales were seen
in the False Pass/Unimak Pass surveys during the spring grey whale
migration. In four instances killer whales were observed feeding
on whale carcasses. The observations from this summer suggest
there may be more transient killer whales in the eastern Aleutians
than we initially suspected, and indicate that we have a great
deal more to learn. Stay tuned for more…
29 September 2003 |
