A large-aperture low-cost hydrophone array for tracking whales from small boats.
05 Nov 2009-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 126, Iss: 5, pp 2248-2256
TL;DR: A passive sonar array designed for tracking diving sperm whales in three dimensions from a single small vessel is presented, and the advantages and limitations of operating this array from a 6 m boat are described.
Abstract: A passive sonar array designed for tracking diving sperm whales in three dimensions from a single small vessel is presented, and the advantages and limitations of operating this array from a 6 m boat are described. The system consists of four free floating buoys, each with a hydrophone, built-in recorder, and global positioning system receiver (GPS), and one vertical stereo hydrophone array deployed from the boat. Array recordings are post-processed onshore to obtain diving profiles of vocalizing sperm whales. Recordings are synchronized using a GPS timing pulse recorded onto each track. Sensitivity analysis based on hyperbolic localization methods is used to obtain probability distributions for the whale’s three-dimensional location for vocalizations received by at least four hydrophones. These localizations are compared to those obtained via isodiachronic sequential bound estimation. Results from deployment of the system around a sperm whale in the Kaikoura Canyon in New Zealand are shown.
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01 Apr 2011Abstract: Acknowledgements Introduction Part I. Underwater Acoustics (The Basics): 1. Principles of underwater sound 2. Cetacean sounds 3. Sonar equation Part II. Signal Processing (Designing the Tools): 4. Detection methods 5. Classification methods 6. Localisation and tracking Part III. Passive Acoustic Monitoring (Putting It All Together): 7. Applications of PAM 8. Detection functions 9. Simulating sampling strategies 10. PAM systems 11. References and literature Index.
135 citations
TL;DR: In this article, the authors used passive acoustic monitoring (PAM) to obtain fine scale geo-referenced tracks of harbor porpoises in tidal rapid areas, where large aperture hydrophone arrays are required to obtain accurate locations of animals from PAM data and automated algorithms are necessary to process the large quantities of acoustic data collected on such systems during a typical survey.
Abstract: The growing interest in generating electrical power from tidal currents using tidal turbine generators raises a number of environmental concerns, including the risk that marine mammals might be injured or killed through collision with rotating turbine blades. To understand this risk, information on how marine mammals use tidal rapid habitats and in particular, their underwater movements and dive behaviour is required. Porpoises, which are the most abundant small cetacean at most European tidal sites, are difficult animals to tag, and the limited size of tidal habitats means that any telemetered animal would be likely to spend only a small proportion of time within them. Here, an alternative approach is explored, whereby passive acoustic monitoring (PAM) is used to obtain fine scale geo-referenced tracks of harbour porpoises in tidal rapid areas. Large aperture hydrophone arrays are required to obtain accurate locations of animals from PAM data and automated algorithms are necessary to process the large quantities of acoustic data collected on such systems during a typical survey. Methods to automate localisation, including a method to match porpoise detections on different hydrophones and separate different vocalising animals, and an assessment of the localisation accuracy of the large aperture hydrophone array are presented.
28 citations
Cites background from "A large-aperture low-cost hydrophon..."
...Widely spaced (or “large aperture”) hydrophone arrays have been used for decades to track the movements of cetaceans underwater (e.g., Watkins and Schevill, 1972; Møhl et al., 2000; Miller and Dawson, 2009; Wiggins et al., 2012)....
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TL;DR: T-POD data suggest that parts of the ‘Dolphin Protection Zone‘, in which boat traffic is restricted, are used frequently while other parts are not, and provide a basis for refining this management tool.
Abstract: Passive acoustic methods are increasingly used to study cetacean habitat use and behaviour. The Timing Porpoise Detector (T-POD; www.chelonia.co.uk) is a self-contained acoustic data logger, which records echolocation by cetaceans. This study used nine T-PODs to document habitat use by bottlenose dolphins in Doubtful Sound, New Zealand, over a 12-month period, collecting data over 76,104 h (of a possible 78,840). T-POD records show that dolphin distribution varied seasonally, with inner fiord sites being used most often in summer and autumn, and outer fiord sites during winter and spring. This seasonal pattern was positively correlated with surface water temperature. Echolocation activity in general and buzzes, which are usually indicative of foraging, were both significantly more common during dawn and/or dusk, suggesting crepuscular foraging. T-POD data suggest that parts of the ‘Dolphin Protection Zone‘, in which boat traffic is restricted, are used frequently while other parts are not, and pr...
26 citations
Cites background from "A large-aperture low-cost hydrophon..."
...…a wide range of techniques are available, ranging from relatively simple self-contained instruments that automatically log echolocation signals (e.g. T-PODs; Carstensen et al. 2006) to hydrophone arrays designed to track diving marine mammals in three dimensions (e.g. Miller & Dawson 2009)....
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01 Oct 2017
TL;DR: Some evidence for circadian patterns in the foraging behaviour of sperm whales is found, which might be related to vertical movements of their prey following the deep scattering layer, and explored the ecological implications of the whales’ foraging preferences on their habitat use.
Abstract: The submarine canyon off Kaikōura (New Zealand) is an extremely productive deep-sea habitat, and an important foraging ground for male sperm whales ( Physeter macrocephalus ). We used high-resolution archival tags to study the diving behaviour of sperm whales, and used the echoes from their echolocation sounds to estimate their distance from the seafloor. Diving depths and distance above the seafloor were obtained for 28 dives from six individuals. Whales foraged at depths between 284 and 1433 m, targeting mesopelagic and demersal prey layers. The majority of foraging buzzes occurred within one of three vertical strata: within 50 m of the seafloor, mid-water at depths of 700–900 m, and mid-water at depths of 400–600 m. Sperm whales sampled during this study performed more demersal foraging than that reported in any previous studies – including at Kaikōura in further inshore waters. This suggests that the extreme benthic productivity of the Kaikōura Canyon is reflected in the trophic preferences of these massive top predators. We found some evidence for circadian patterns in the foraging behaviour of sperm whales, which might be related to vertical movements of their prey following the deep scattering layer. We explored the ecological implications of the whales’ foraging preferences on their habitat use, highlighting the need for further research on how submarine canyons facilitate top predator hotspots.
25 citations
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...D) passive acoustic array (Miller & Dawson 2009, Miller et al. 2013)....
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...Passive acoustic studies using three-dimensional arrays (e.g., Wahlberg 2002, Miller & Dawson 2009, Miller et al. 2013) are an alternative research tool, with the advantage of providing high-resolution georeferenced 3D locations for relating whale movement and behaviour to their physical…...
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TL;DR: A model-based TDOA method is extended to deal with multiple-animal datasets in a way that does not require a TDOA association step; animals are separated based on position and represent a useful new tool in the suite of options available for tracking multiple animals with passive acoustics.
Abstract: Most methods used to track marine mammals with passive acoustics require that time differences of arrivals (TDOAs) are established and are associated between hydrophone pairs. Consequently, multiple animal trackers commonly apply single-animal TDOA localization methods after performing a call separation and/or TDOA association step. When a wide-baseline array is used with multiple animals that make similar calls with short inter-call-intervals, the separation/association step can be challenging and potentially rejects valid TDOAs. This paper extends a model-based TDOA method to deal with multiple-animal datasets in a way that does not require a TDOA association step; animals are separated based on position. Advantageously, false TDOAs (e.g., a direct path associated with a multipath arrival) do not need to be removed. An analogous development is also presented for a model-based time of arrival tracking method. Results from simulations and application to a multiple sperm whale dataset are used to illustrate the multiple-animal methods. Although computationally more demanding than most track-after-association methods because separation is performed in a higher-dimensional space, the methods are computationally tractable and represent a useful new tool in the suite of options available for tracking multiple animals with passive acoustics.
24 citations
References
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TL;DR: Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.
Abstract: 1. Digital tags were used to describe diving and vocal behaviour of sperm whales during 198 complete and partial foraging dives made by 37 individual sperm whales in the Atlantic Ocean, the Gulf of Mexico and the Ligurian Sea. 2. The maximum depth of dive averaged by individual differed across the three regions and was 985 m (SD = 124.3), 644 m (123.4) and 827 m (60.3), respectively. An average dive cycle consisted of a 45 min (6.3) dive with a 9 min (3.0) surface interval, with no significant differences among regions. On average, whales spent greater than 72% of their time in foraging dive cycles. 3. Whales produced regular clicks for 81% (4.1) of a dive and 64% (14.6) of the descent phase. The occurrence of buzz vocalizations (also called 'creaks') as an indicator of the foraging phase of a dive showed no difference in mean prey capture attempts per dive between regions [18 buzzes/dive (7.6)]. Sperm whales descended a mean of 392 m (144) from the start of regular clicking to the first buzz, which supports the hypothesis that regular clicks function as a long-range biosonar. 4. There were no significant differences in the duration of the foraging phase [28 min (6.0)] or percentage of the dive duration in the foraging phase [62% (7.3)] between the three regions, with an overall average proportion of time spent actively encountering prey during dive cycles of 0.53 (0.05). Whales maintained their time in the foraging phase by decreasing transit time for deeper foraging dives. 5. Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.
364 citations
TL;DR: A new equation for the speed of sound in sea water has been developed with validity not only for realistic combinations of the parameters salinity, temperature, and pressure, but with extension to pure water as well.
Abstract: A new equation for the speed of sound in sea water has been developed with validity not only for realistic combinations of the parameters salinity, temperature, and pressure, but with extension to pure water as well. This new equation, referred to as NRL II, has a standard deviation of 0.05 m/sec. Tables are presented comparing calculations using this new model to each of eight earlier equations. Graphs are also included indicating approximate corrections that could be applied to existing sound speed profiles, but it is recommended that such profiles be recalculated and new ones obtained according to NRL II.
350 citations
TL;DR: In this paper, the authors estimate the abundance of sperm whales in a 7.8 million km 2 study area in the eastern temperate North Pacific using data from a ship-based acoustic and visual line-transect survey in spring 1997.
Abstract: We estimate the abundance of sperm whales in a 7.8 million km 2 study area in the eastern temperate North Pacific using data from a ship-based acoustic and visual line-transect survey in spring 1997. Sperm whales were detected acoustically using a hydrophone array towed at 15 km/h and 100 m depth. The hydrophone array was towed for 14,500 km, and locations were estimated acoustically for 45 distinct sperm whale groups. Whales producing slow clicks (.2-s period) were detected at greater distance (up to 37 km), and the estimation of effective strip widths was stratified based on initial click period. Visual survey effort (using 253 binoculars and naked eyes) covered 8,100 km in Beaufort sea states 0‐5 and resulted in only eight sightings. The effective strip width for visual detections was estimated from previous surveys conducted using the same methods and similar vessels in the eastern Pacific. Estimated sperm whale abundance in the study area was not significantly different between acoustic (32,100, CV ¼0.36) and visual (26,300, CV ¼0.81) detection methods. Acoustic techniques substantially increased the number of sperm whales detected on this line-transect survey by increasing the range of detection and allowing nighttime surveys; however, visual observations were necessary for estimating group size.
241 citations