A Review and Inventory of Fixed Autonomous Recorders for Passive Acoustic Monitoring of Marine Mammals

Abstract

Fixed autonomous acoustic recording devices (autonomous recorders [ARs]) are defined as any electronic recording system that acquires and stores acoustic data internally (i.e., without a cable or radio link to transmit data to a receiving station), is deployed semi-permanently underwater (via a mooring, buoy, or attached to the sea floor), and must be retrieved to access the data. More than 30 ARs were reviewed. They varied greatly in capabilities and costs, from small, hand-deployable units for detecting dolphin and porpoise clicks in shallow water to larger units that can be deployed in deep water and can record at high-frequency bandwidths for over a year, but must be deployed from a large vessel. The capabilities and limitations of the systems reviewed herein are discussed in terms of their effectiveness in monitoring and studying marine mammals.

Effects of duty-cycled passive acoustic recordings on detecting the presence of beaked whales in the northwest Atlantic

“…Over the past several decades, this method has been applied most extensively to record low-frequency vocalizations from baleen whales, and is particularly valuable for monitoring remote locations and detecting rare or elusive species infrequently encountered at sea (e.g., Mellinger et al, 2007;Sousa-Lima et al, 2013). Recent technological improvements in the performance of autonomous recorders have led to the increasing use of PAM to detect higher frequency signals, including odontocete echolocation (Sousa-Lima et al, 2013). This approach has particular value for studying beaked whales (family Ziphiidae), which are among the most difficult cetacean species to observe due to their offshore distributions and deep-diving behavior.…”

“…particularly at such high sampling rates (Sousa-Lima et al, 2013). Recorder deployment and recovery is both costly and logistically challenging, so the collection of highfrequency data for prolonged periods often involves a reduced recording schedule, employing a duty cycle to extend the duration of each deployment (e.g., Au et al, 2013).…”

“…However, it is important to consider any biases that may be introduced by using a reduced recording schedule (Thomisch et al, 2015). If the duty cycle listening period and recording interval are not appropriately matched to the duration and timing of acoustic events of interest, potential detections may be missed and species occurrence underestimated (Miksis-Olds et al, 2010;Sousa-Lima et al, 2013;Thomisch et al, 2015).…”

Abundance estimate of the Amazon River dolphin (Inia geoffrensis) and the tucuxi (Sotalia fluviatilis) in southern Ucayali, Peru

“…This technology also has certain disadvantages. Animals can only be detected when making noise, analysis of acoustic data files can be difficult and time consuming, and positive species identification is often challenging (Rayment et al, 2009;Sousa-Lima et al, 2013). A variety of equipment, such as hydrophones, Acoustic tags (A-Tags), and Cetacean Porpoise Click Detectors (C-PODs) have been developed to meet different study needs (Nielsen & Møhl, 2006;Marques et al, 2009;Gallus et al, 2012).…”

Monitoring the habitat use of common Bottlenose Dolphins (Tursiops truncatus) using passive acoustics in a Mediterranean marine protected area

“…PAM is a good technique for studying cetaceans because acoustics is often the only tool allowing the study of submerged animals that are not visible to human observers and it does not interfere with animal behaviour (Zimmer, 2011). In particular, autonomous recorders were chosen because they are more flexible as regards configuration, timing, and location of deployment, and they are less obtrusive to both animals and boat traffic when compared to other types of PAM systems (Sousa- Lima et al, 2013). Thus, the main aims of this study were: i) to detect the spatial and temporal trends in bottlenose dolphin habitat use and boat traffic and ii) to assess if boat traffic elicited displacement responses in bottlenose dolphins, influencing habitat use.…”