Abstract:
APIS (Antarctic Pack Ice Seals) was an international program
formulated by the SCAR Group on Specialists on Seals to consider the
functional significance of upper trophic level predators in the
Antarctic pack ice zone and to investigate the seals' interactions
with their biological and physical environment. The US component
assessed prey, predators, and environmental
... variables in the eastern
Ross Sea (ca. 67 - 77.5 degrees S and 129 - 180 degrees W) from
December 1999 to February 2000.
This data set contains acoustic data collected using a Hydroacoustics
Technology Inc. (HTI) Model 244 Multi-Frequency System with two
transducers (38 and 120 kHz) operating on fast-multiplexed mode. Data
collection includes real-time integration of the acoustic signal in 1
m depth bins and the raw, unthresholded digitized signal stored on
Digital Audio Tapes. Sixteen gigabytes of integrated acoustic data
were collected plus 54 DAT tapes of raw data. All data were collected
using a FM slide (chirp) coded 5 ms pulses, with a slide bandwidth of
10 kHz. Matched filter processing of these pulses resulted in an
effective pulse resolution (output pulse width) of 0.18 ms. The DAT
tapes were reprocessed to correct for calibration offsets based on
field standard target sphere measurements and to correct for noise
interference for the 120 kHz data. The 38 kHz data was not reanalyzed
as it contained much higher and variable noise interference. Data are
available as relative backscattering (SV) and as absolute estimates of
target density based on in situ sigma scaling. The reprocessing was
performed by HTI. 
