Abstract:
Descriptions of seasonal occurrence and behaviour of Antarctic blue and fin whales
in the Southern Ocean are of pivotal importance for the effective conservation and management
of these endangered species. We used an autonomous acoustic recorder to collect bioacoustic data
from January through September 2014 to describe the seasonal occurrence, behaviour and detection ranges of Antarctic blue and fin whale calls off the Maud Rise, Antarctica. From 2479 h of
recordings, we detected D- and Z-calls plus the 27 Hz chorus of blue whales, the 20 and 99 Hz
pulses of fin whales and the 18−28 Hz chorus of blue and fin whales. Blue whale calls were
detected throughout the hydrophone deployment period with a peak occurrence in February,
indicating continuous presence of whales in a broad Southern Ocean area (given the modelled
detection ranges). Fin whale calls were detected from January through July when sea ice was
present on the latter dates. No temporal segregation in peaks of diel calling rates of blue and fin
whales was observed in autumn, but a clear temporal segregation was apparent in summer.
Acoustic propagation models suggest that blue and fin whale calls can be heard as far as 1700 km
from the hydrophone position in spring. Random forest models ranked month of the year as the
most important predictor of call occurrence and call rates (i.e. behaviour) for these whales. Our
work highlights areas around the Maud Rise as important habitats for blue and fin whales in the
Southern Ocean.
