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Cetacean population density estimation from single fixed sensors using passive acoustics
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Image of FIG. 1.
FIG. 1.

Distribution of AUTEC’s hydrophones showing the single sensor (#57) used in this paper’s analysis, and the sensors used in ambient noise measurements.

Image of FIG. 2.
FIG. 2.

Whale orientation and respective angles. Upper diagrams show whale heading and pitch, and lower diagrams show whale heading and elevation angle with respect to the hydrophone. These angles are necessary to estimate the acoustic off-axis angle between whale and hydrophone (see text).

Image of FIG. 3.
FIG. 3.

Attenuation of source level as a function of off-axis angle for Blainville’s beaked whales, estimated by using a piston model with radius of 16 cm.

Image of FIG. 4.
FIG. 4.

Sound speed as a function of depth measured in spring at the AUTEC range and used as input for the transmission loss calculations.

Image of FIG. 5.
FIG. 5.

Transmission loss as a function of range, or distance between source and receiver, for 3 different depths: (top) 400, (middle) 800, and (bottom) 1200 m. The different curves represent results of calculations for the coherent (gray) and incoherent (solid black) acoustic fields as well as the spherical spreading law with frequency-dependent attenuation α = 8.9 dB/km (dashed).

Image of FIG. 6.
FIG. 6.

High-frequency ambient noise levels, integrated over 24–48 kHz, measured at five different hydrophones at AUTEC and used in the Monte Carlo simulations.

Image of FIG. 7.
FIG. 7.

Probability of detection (P) as a function of signal-to-noise ratio (SNR), estimated by fitting a binary generalized additive model (GAM) to the manually annotated detections. The vertical lines on the top of the figure correspond to the manually detected clicks that were also detected by the FFT detector, and the ones at the bottom correspond to the manually detected clicks that were not detected by the FFT detector. Circles summarize the data, showing the proportion detected in 8 successive intervals, each containing 1/8 of the measured clicks; the vertical lines above and below each circle indicate 95% binomial confidence intervals for each proportion. Solid line shows estimate from the GAM, and dashed lines are 95% pointwise confidence intervals. The fall-off in detection probability at high SNR is discussed in the text.

Image of FIG. 8.
FIG. 8.

Estimated detection function as a function of slant distance for three angles measured from the whale’s acoustic axis: 0° (solid), 45° (dashed), and 90° (dotted).

Image of FIG. 9.
FIG. 9.

Average probability of detection from the 10 000 simulated clicks for each realization of energy flux density taken from a Gaussian distribution.


Generic image for table

Values used to estimate whale clicking depth z and pitch β for three distinct dive phases. Click proportion is an estimate of the fraction of clicks produced during each dive phase. Mean depth and standard deviation (in parentheses) are used in Gaussian distributions for sampling clicking depths. Pitch distribution indicates the distribution used for each dive phase, the pitch range, and values used for the required distribution parameters. Negative pitch is measured downwards.

Generic image for table

Source levels of beaked whales, Ziphius cavirostris (Zc) and Mesoplodon densirostris (Md), available in the literature. Source levels are in dB re 1 µPa at 1 m. Note that RMS values can vary depending on the window length used.

Generic image for table

Vocal behavior data for beaked whales, Ziphius cavirostris (Zc) and Mesoplodon densirostris (Md), available in the literature and used for estimating click production rate. The inter-click interval (ICI), mean click duration, duration of deep foraging dives, the amount of time spent clicking during each dive, the IDI (or inter-deep-dive interval), and the number of buzz clicks produced per foraging dive are derived from acoustic tag studies.

Generic image for table

Summary of the values derived for each parameter needed to estimate density of Blainville’s beaked whale at AUTEC using Eq. (1), and their associated CVs.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Cetacean population density estimation from single fixed sensors using passive acoustics