Seasonality of blue and fin whale calls and the influence of sea ice in
the Western Antarctic Peninsula. 2004. Ana Sirovic, John A. Hildebrand,
Sean M. Wiggins, Mark A. McDonald, Sue E. Moore and Deborah Thiele.
Deep-Sea Research II, 51: 2327?2344.
Abstract
The calling seasonality of blue (Balaenoptera musculus) and fin (B.
physalus) whales was assessed using acoustic data recorded on seven
autonomous acoustic recording packages (ARPs) deployed from March 2001
to February 2003 in the Western Antarctic Peninsula. Automatic detection
and acoustic power analysis methods were used for determining presence
and absence of whale calls. Blue whale calls were detected year round,
on average 177 days per year, with peak calling in March and April, and
a secondary peak in October and November. Lowest calling rates occurred
between June and September, and in December. Fin whale calling rates
were seasonal with calls detected between February and June (on average
51 days/year), and peak calling in May. Sea ice formed a month later and
retreated a month earlier in 2001 than in 2002 over all recording sites.
During the entire deployment period, detected calls of both species of
whales showed negative correlation with sea ice concentrations at all
sites, suggesting an absence of blue and fin whales in areas covered
with sea ice. A conservative density estimate of calling whales
from the acoustic data yields 0.43 calling blue whales per 1000 nmi2
and 1.30 calling fin whales per 1000 nmi2, which is about one-third
higher than the density of blue whales and approximately equal to the
density of fin whales estimated from the visual surveys.
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