Table 1.
Summary details of the recorded harbour porpoise acoustic signals. General observation refers to a free-swimming porpoise scanning the environment; Object investigation refers to targeted high repetition signals used to identify target objects.
Fig 1.
Left: Map showing the locations of the two transect lines conducted for the playback experiment, with playback stations at increments of 100m to 600m from the PAM devices indicated by individual points.
Grey box indicates the position of the moored PAM devices. Note that the moored devices were in slightly different latitudinal/longitudinal positions between the morning and afternoon due to slight movement due to currents and tide, the distance between the two points was 35m. Inset map shows the location of the experimental site in the context of Ireland. Right: Diagram of mooring set-up for the PAM devices.
Table 2.
Number of detected playbacks at each playback station for each device. A total of 40 playbacks were transmitted at each station across all recordings combined, including both gain settings, with 8 playbacks per individual recording. Results are presented for all recordings combined and further classified by individual recording.
Table 3.
Final model summaries including deviance explained (Dev. Expl.) for GAMs investigating the factors affecting the detection of harbour porpoise playbacks for all PAM devices. Significant interactions are indicated by p-value < 0.05, and bold text. Dashes indicate that the factor was excluded in the model selection process. AIC values for model selection shown in supplement material (see S2 File).
Table 4.
Calculated Effective Detection Radii (EDR) and Effective Detection Area for the PAM devices, and EDR for the playback of distinct call types.
Fig 2.
Estimated probability of detection of all harbour porpoise playbacks (solid smooth lines) and 95% bootstrap confidence intervals (smooth dashed lines and shaded area) for A) SoundTrap, B) F-POD, and C) C-POD.
Fig 3.
Detection ranges of SoundTrap, F-POD and C-POD shown as Effective Detection Radius (EDR), and Effective Detection Area (EDA) based on the detection probability of harbour porpoise playbacks.
Date of experiment: 02/04/2023. Estimated probability of detection of the playback of all harbour porpoise vocalisations (solid smooth lines) and 95% bootstrap confidence intervals (smooth dashed lines) for A) SoundTrap, B) F-POD, and C) C-POD.