Streamlining analysis methods for large acoustic surveys using automatic detectors with operator validation

Abstract

Passive acoustic surveys are becoming increasingly popular as a means of surveying for cetaceans and other marine species. These surveys yield large amounts of data, the analysis of which is time consuming and can account for a substantial proportion of the survey budget. Semi‐automatic processes enable the bulk of processing to be conducted automatically while allowing analyst time to be reserved for validating and correcting detections and classifications. Existing modules within the Passive Acoustic Monitoring software PAMGuard were used to process a large (25.4 Terabyte) dataset collected during towed acoustic ship transits. The recently developed ‘Multi‐Hypothesis Tracking Click Train Detector’ and the ‘Whistle and Moan Detector’ modules were used to identify occasions within the dataset at which vocalising toothed whales (odontocetes) were likely to be acoustically present. These putative detections were then reviewed by an analyst, with false positives being corrected. Target motion analysis provided a perpendicular distance to odontocete click events enabling the estimation of detection functions for both sperm whales and delphinids. Detected whistles were assigned to the lowest taxonomical level possible using the PAMGuard ‘Whistle Classifier’ module. After an initial tuning process, this semi‐automatic method required 91 hr of an analyst's time to manually review both automatic click train and whistle detections from 1,696 hr of survey data. Use of the ‘Multi‐Hypothesis Tracking Click Train Detector’ reduced the amount of data for the analyst to search by 74.5%, while the ‘Whistle and Moan Detector’ reduced data to search by 85.9%. In total, 443 odontocete groups were detected, of which 55 were from sperm whale groups, six were from beaked whales, two were from porpoise and the remaining 380 were identified to the level of delphinid group. An effective survey strip half width of 3,277 and 699 m was estimated for sperm whales and delphinids respectively. The semi‐automatic workflow proved successful, reducing the amount of analyst time required to process the data, significantly reducing overall project costs. The workflow presented here makes use of existing modules within PAMGuard, a freely available and open‐source software, readily accessible to acoustic analysts.

Threatened cetaceans off the coast of Israel and long‐range movement of a sperm whale

“…Acoustic .wav files were analysed according to Webber et al (2022) in PAMGuard Viewer mode. A visual survey was conducted during daylight hours of the acoustic survey to provide additional information on cetacean presence and where possible data on species identity, location, numbers of animals and behaviour.…”

“…Data from the SAIL acquisition card were written as four‐channel 16‐bit lossless .wav files using PAMGuard (Gillespie et al, 2009, available at http://www.pamguard.org), which also carried out real‐time acoustic processing and logged the ship location from GPS. Acoustic .wav files were analysed according to Webber et al (2022) in PAMGuard Viewer mode. A visual survey was conducted during daylight hours of the acoustic survey to provide additional information on cetacean presence and where possible data on species identity, location, numbers of animals and behaviour.…”

Automated Detection and Tracking of Marine Mammals in the Vicinity of Tidal Turbines Using Multibeam Sonar

“…The software was developed as a plugin for the PAMGuard passive acous-tic software [30] to utilise the existing PAMGuard infrastructure for automatic processing, followed by human operator browsing and annotation of large datasets. Our workflow for processing sonar data is broadly similar to that for passive acoustic data described in [31] for the monitoring of cetaceans, where automatic detectors are initially applied to a large dataset to detect candidate vocalisations, which are then manually checked and further annotated by an operator viewing sophisticated data displays.…”