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This initiative used the first-ever
application of 3-D backpacks
and the customized 'seal beanie.'
Although seal beanies are
commonly used to track seals,
Thomas' innovation allowed us to
study the interaction between seals
and juvenile salmon, and provided
the first ever direct measure of
predation rates on individual salmon.
3. Determining harbour seal predation on
juvenile salmon
Harbour seals can consume a large number of juvenile
Chinook and Coho Salmon when the fish first enter marine
waters. But their rate of predation may not be as large as
people speculate. Past estimates were based on only a
couple of years of sampling scats from Cowichan Bay and
other areas of the Strait of Georgia. Those studies used the
hard parts that remained in the scat as means to identify
the species eaten. The problem is that we were unable to
determine the age, species, origin or numbers of salmon
in these samples. A new research technique was devel-
oped through the Salish Sea Marine Survival Project to
directly estimate the rate of predation on a release of
hatchery Coho Salmon from Big Qualicum Hatchery.
This research study — conducted by the Marine Mammal
Research Unit at University of British Columbia (UBC) un-
der Dr. Andrew Trites in cooperation with BC Conservation
Foundation — involved using DNA techniques to identify
prey in seal scats, the development of 'seal beanies' to
detect Passive Integrated Transponder (PIT ) tags placed in
salmon, and the application of customized 3-D backpacks
to track the activity, including the feeding behaviour, of
these seals (Figure 3).
The seal beanies are the creation of Austen Thomas and
Brian Battaile, who were both PhD students at UBC during
SSMSP. Thomas and Battaile designed a circular antenna
for the beanie that could detect a PIT tag as a seal con-
sumed it. When a seal fed on a tagged salmon and then
hauled out of marine waters to rest, the tag's information
captured by the beanie was automatically transmitted to
a satellite, then down to Austen's lab at UBC. PIT tags emit
a unique ID meaning salmon can be individually counted
when consumed.
Figure 2. BCCF staff PIT tagging juvenile Chinook on a purse seine in Cowichan Bay.
Figure 3. Seal experts outfit an anaesthetized seal. No seals were
harmed during the project. Photo by Dennis Frost.
