Passive Acoustic Recordings Research Articles

Exploring spatial and temporal trends in the soundscape of an ecologically significant embayment

The Hauraki Gulf, a shallow embayment in north-eastern New Zealand, provides an interesting environment for ecological soundscape research. It is situated on a tectonic plate boundary, contains one of the busiest ports in the southern hemisphere and is home to a diverse range of soniferous animals. The underwater soundscape was monitored for spatial and temporal trends at six different listening stations using passive acoustic recorders. The RMS sound pressure level of ambient sound (50–24,000 Hz) at the six listening stations was similar, ranging from 90–110 dB re 1 μPa throughout the recording period. Biophony had distinct temporal patterns and biological choruses of urchins were significantly correlated to temperature. Geophony and biophony followed the acoustic niche hypothesis, where each sound exhibited both temporal and frequency partitioning. Vessel passage sound were identified in 1.9–35.2% of recordings from the different listening stations. Vessel sound recorded in the Hauraki Gulf has the potential to mask concurrent geophony and biophony, sounds that may be important to marine life. This study provides a baseline of ambient sound, useful for future management strategies in shallow embayments where anthropogenic pressure is likewise increasing.

Temporal and spatial distribution patterns of toothed whales in Massachusetts Bay using passive acoustics from ocean gliders

Basic information on marine mammal habitat use is necessary for informing ecosystem-based management plans and for mitigating human impacts. Massachusetts Bay is an important marine mammal foraging area in the Gulf of Maine and a region of high human activity, but little is known about toothed whale habitat use, particularly during winter months. Passive acoustic monitoring, particularly from autonomous platforms, provides advantages in studying habitat use in unfavorable conditions. The goal of this work is to use acoustic monitoring to investigate temporal and spatial occurrence patterns of toothed whale species in Massachusetts Bay during late fall/early winter using ocean gliders equipped with passive acoustic recorders. Slocum gliders were deployed in western Massachusetts Bay in 2014, 2015, and 2016. Toothed whales were detected on 92 (72%) of 128 deployment days. Detections occurred more often at night. Ongoing work includes acoustic identification of species and assessing relationships between detections and environmental conditions. These data provide the first evidence of a consistent presence of toothed whales in Massachusetts Bay during late fall and winter, and demonstrate the potential for ocean gliders as a tool to detect toothed whales in areas/times that are difficult to survey with traditional visual methods.

Not all snaps are from shrimp: Broadband, impulsive sounds from different benthic organisms can provide information on animal presence and behavior

Snapping shrimp are a dominant source of sound in many marine environments; however, there are several other benthic organisms which produce broadband, impulsive sounds as part of their daily activity. We used a passive acoustic recorder with a video camera to identify and categorize the soniforous behaviors of several different species (fish and bivalves) in both laboratory and field environments. Bay scallops (Argopecten irradians) in shallow water estuaries in New York “cough” when they move via jet propulsion as well as to clean their filter feeding apparatus. Additionally, the substrate they are “scooting” on can alter the characteristics of their “cough.” Parrotfish (multiple species) “chomp” as they forage on seagrasses and surgeonfish (Acanthuridae) “scrape” algae from hard substrates in Caribbean lagoons. We investigated whether these signals can be distinguished from other broadband sounds occurring in the marine environment and, if so, how longer-duration passive acoustic recordings can be used to monitor the abundance or behaviors of these animals.

Designing a scalable passive acoustics network

To realize the potential of passive acoustics to study animal distribution and behavior over large spatial and temporal scales, systems capable of processing acoustic data remotely and transmitting those results to cloud systems are needed. Passive acoustic recorders have been important for allowing researchers to collect large amounts of data over long time periods, but they allow the decision of how to analyze the data to be delayed until after it is collected. Given the availability of inexpensive computing and cloud connectivity, one key challenge in developing a scalable passive acoustics network is deciding what is important to know. A prototype scalable passive acoustics node to detect dolphin whistles and measure sound levels corresponding to fish sounds, boat noise, and snapping shrimp has been developed. The decision was made to bin data over 10 minute periods (e.g., whistles per 10 minutes), and store only small amounts of raw data for quality control. The system takes advantage of recent developments in consumer level Internet of Things (IoT) tools so that the hardware is inexpensive and the cloud system can handle very large numbers of nodes.

Passive acoustic monitoring finds concurrent use of an artificial reef in the New York Bight by foraging humans and odontocetes (Tursiops truncatus)

Passive acoustic recordings collected during summer 2015 at an artificial reef (sunken barge) south of Long Island, New York revealed regular visitation by groups of delphinid odontocetes. Detected signals included social (whistles) and foraging (short-interval echolocation) signals of odontocetes, as well as signals specific to bottlenose dolphins (Tursiops truncatus) and two known prey species. Visual observations, high broadband noise levels, and presence of acoustic signatures specific to boats indicated heavy use of this site by recreational fishers. Boat detections were significantly more frequent on weekends and between sunrise and sunset. Dolphin detections did not vary diurnally and were significantly lower on weekends, possibly due to avoidance of persistent noise disturbance. Bottlenose dolphins produce low-frequency, narrow-band signals that are highly susceptible to masking by boat noise. However, no significant difference was observed in the duration, average peak frequency, or frequency range of these signals when boat noise was present or absent. Our findings demonstrate the benefits of passive acoustic techniques in monitoring soniforous users (including humans) of artificial reef habitats in these waters. Attraction of both human fishers and odontocetes to artificial reefs may increase direct human-predator interactions as well as indirect ecological competition.

Large scale passive acoustic recording efforts improve our understanding of long term changes in marine mammal ecology and distribution

Collaborative efforts across a large number of scientists working throughout the Western Atlantic Ocean has led to sharing of passive acoustic data spanning over a decade. These data allow for a 24/7 lens to be cast providing a long term temporal understanding of species presence. This collaborative approach has allowed for unprecedented research focusing on long term patterns and changes in distribution and movements of baleen whales and odontocetes. Results from these data shows how baleen whales migration paths can be defined and changes in these paths can be detected over time. Additionally, they show that whales are present at times of the year and in regions that were not previously documented, particularly during winter months. Beaked whale composition within and between each shelf break canyon where recordings are available varies considerably, demonstrating latitudinal as well as regional gradients in species presence. The addition of ambient noise curves to this mix provides context and allows for the evaluation of anthropogenic noise. This long term big picture view of species presence and movements improves our capacity to infer whether observed changes are a result of ecological, climatological, or anthropogenic factors.

Characterizing soundscapes and larval fish settlement in tropical seagrass and mangrove habitats

Recent evidence suggests soundscapes of coral reefs may provide acoustic cues that larval reef fish utilize during settlement. Seagrass and mangrove habitats are further important refuges for larvae and juveniles of many fishes; however, compared to reefs, less is known about the characteristics of tropical seagrass and mangrove soundscapes and their potential as settlement cues. We deployed light traps to assess fish larvae settlement and passive acoustic recorders to study the “ecoacoustics” at mangrove, seagrass, and coral reef sites around two bays in St. John, U.S. Virgin Islands. Light traps were deployed nightly around the third quarter and new moon, and 24 h periods of acoustic recordings were taken during the same time. Fish larvae were counted and identified to the lowest possible taxonomic level. Focusing on biotic soundscape components, diel trends in metrics such as sound pressure level, power spectral density, and snap counts of snapping shrimp were assessed. Although what role mangrove and seagrass soundscapes may play in fish settlement remains unclear, these soundscape and larval settlement data provide foundations for deeper investigations of the relationship between acoustic and larval ecology in these essential nursery habitats.

Nocturnal patterns in fish chorusing off the coasts of Georgia and eastern Florida

Fish chorusing is a major component of the marine acoustic environment, and much of this chorusing activity happens at night. These nocturnal sounds are commonly associated with reproductive behavior. For many co-occurring taxa, increases in vocal activity may intensify acoustic competition within a constrained signaling environment; for nocturnal species, there is a limited time window for these critical behaviors, and competition to be heard by conspecifics likely increases. Using passive acoustic recording units deployed in the nearshore waters off Georgia and eastern Florida, we evaluated the nocturnal acoustic habits of fishes and examined how the sounds from nocturnal fish chorusing contribute to the overall soundscape. We examined long-term spectrograms for spatial and temporal patterns of fish calling. Black drum [Pogonias cromis (Linnaeus, 1766)] and toadfish (Opsanus sp.) dominated the nocturnal acoustic scene, but calls of other identified [e.g., red drum, Sciaenops ocellatus (Linnaeus, 1766); silver perch, Bairdiella chrysoura (Lacepede, 1802)] and unidentified calling species also occur. We examined the acoustic indices of entropy, acoustic diversity, and acoustic complexity to compare nocturnal and diurnal fish calling activity across the region. When sustained fish chorusing activity increases, entropy and acoustic diversity decrease, but acoustic complexity increases. With the acoustic differences in composition of nocturnally- and diurnally-active species groups, there is a different nocturnal soundscape than during the day. Passive acoustic surveys represent an exciting approach to understand the nocturnal reproductive activity of coastal fishes.

Potential of passive acoustic recording for monitoring invasive species: freshwater drum invasion of the Hudson River via the New York canal system

We conducted a preliminary passive acoustic survey of the occurrence of freshwater drum, Aplodinotus grunniens, in the New York State Canal System (NYSCS) to demonstrate the usefulness of underwater sound monitoring in invasive species studies. Data from known populations of freshwater drum in Dale Hollow Reservoir and J. Percy Priest Lake in Tennessee and Lake Champlain in New York were used to validate freshwater drum call characteristics. Similar to more well studied marine members of the Sciaenidae, freshwater drum calls are composed of highly variable trains of 1–119 knocks call−1 (mean = 25 knocks call−1), a mean knock period of 33 knocks s−1, mean peak frequency of 400 Hz, and mean duration of 0.8 s. The occurrence of drum chorus calls at many locations within the NYSCS indicates likely spawning throughout the system, and suggests the possibility that individuals have invaded the Hudson River from native populations of Lake Champlain, Lake Erie, and Lake Ontario. We point out that the species has been excluded from the east coast of North America throughout history by geographic barriers, and it would have been impossible for the species to gain entrance to the Hudson without the NYSCS, or direct introduction, and thus it is a true invasive which will likely have a dramatic impact on the Hudson River ecosystem. We suggest that freshwater drum most likely also invaded Lakes Oneida, Onondaga, Cayuga and Seneca through the NYSCS. We conclude that passive acoustic surveys are a highly effective non-invasive tool to monitor the distribution of soniferous invasive organisms in aquatic systems, and promise to be especially useful in documenting the future spread of freshwater drum in the Hudson River system.

Measuring the Marine Soundscape of the Indian Ocean with Southern Elephant Seals Used as Acoustic Gliders of Opportunity

AbstractThe underwater ambient sound field contains quantifiable information about the physical and biological marine environment. The development of operational systems for monitoring in an autonomous way the underwater acoustic signal is necessary for many applications, such as meteorology and biodiversity protection. This paper develops a proof-of-concept study on performing marine soundscape analysis from acoustic passive recordings of free-ranging biologged southern elephant seals (SES). A multivariate multiple linear regression (MMLR) framework is used to predict the measured ambient noise, modeled as a multivariate acoustic response, from SES (depth, speed, and acceleration) and environmental (wind) variables. Results show that the acoustic contributions of SES variables affect mainly low-frequency sound pressure levels (SPLs), while frequency bands above 3 kHz are less corrupted by SES displacement and allow a good measure of the Indian Ocean soundscape. Also, preliminary results toward the development of a mobile embedded weather sensor are presented. In particular, wind speed estimation can be performed from the passive acoustic recordings with an accuracy of 2 m s−1, using a rather simple multiple linear model.

Mapping the Soundscape Off the Southeastern USA by Using Passive Acoustic Glider Technology

AbstractThe purpose of this study was to explore the soundscape of shelf‐edge Atlantic waters of the southeastern USA (SEUS) during winter by using passive acoustic and autonomous glider technologies, with a focus on the distribution of groupers. An autonomous glider was deployed off the SEUS coast near Cape Canaveral, Florida, on March 3, 2014, and transited to Cape Fear, North Carolina, where it was retrieved on April 1, 2014. Using satellite and hydrodynamic model data for guidance, the glider piloted in and out of the Gulf Stream, taking advantage of the high currents to reach the targeted sampling area. Ambient noise was recorded by an integrated passive acoustic recorder during the 29‐d mission, in which the glider traveled 895 km and reached waters 267 m deep. A variety of sounds was identified in the acoustic recordings, including sounds generated by Red Grouper Epinephelus morio and toadfishes Opsanus sp.; two sounds previously documented in the Gulf of Mexico that were suspected to be produced by fish; whistles and echolocation from marine mammals; and extensive vessel noise. Numerous sounds from previously undocumented sources were also recorded. The Red Grouper was the only serranid that was consistently identified from the sound data, with detections occurring within and outside of South Atlantic Fishery Management Council marine protected areas. This research demonstrates the potential utility of a glider‐based passive acoustic approach as a component of a program to map fish, marine mammal, and vessel distributions over large scales.

Calling at the highway: The spatiotemporal constraint of road noise on Pacific chorus frog communication.

Loss of acoustic habitat due to anthropogenic noise is a key environmental stressor for vocal amphibian species, a taxonomic group that is experiencing global population declines. The Pacific chorus frog (Pseudacris regilla) is the most common vocal species of the Pacific Northwest and can occupy human‐dominated habitat types, including agricultural and urban wetlands. This species is exposed to anthropogenic noise, which can interfere with vocalizations during the breeding season. We hypothesized that Pacific chorus frogs would alter the spatial and temporal structure of their breeding vocalizations in response to road noise, a widespread anthropogenic stressor. We compared Pacific chorus frog call structure and ambient road noise levels along a gradient of road noise exposures in the Willamette Valley, Oregon, USA. We used both passive acoustic monitoring and directional recordings to determine source level (i.e., amplitude or volume), dominant frequency (i.e., pitch), call duration, and call rate of individual frogs and to quantify ambient road noise levels. Pacific chorus frogs were unable to change their vocalizations to compensate for road noise. A model of the active space and time (“spatiotemporal communication”) over which a Pacific chorus frog vocalization could be heard revealed that in high‐noise habitats, spatiotemporal communication was drastically reduced for an individual. This may have implications for the reproductive success of this species, which relies on specific call repertoires to portray relative fitness and attract mates. Using the acoustic call parameters defined by this study (frequency, source level, call rate, and call duration), we developed a simplified model of acoustic communication space–time for this species. This model can be used in combination with models that determine the insertion loss for various acoustic barriers to define the impact of anthropogenic noise on the radius of communication in threatened species. Additionally, this model can be applied to other vocal taxonomic groups provided the necessary acoustic parameters are determined, including the frequency parameters and perception thresholds. Reduction in acoustic habitat by anthropogenic noise may emerge as a compounding environmental stressor for an already sensitive taxonomic group.

Beluga whales in the western Beaufort Sea: Current state of knowledge on timing, distribution, habitat use and environmental drivers

The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from aerial surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An aerial survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the aerial survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.

Passive acoustic recording of Ophidion rochei calling activity in Calvi Bay (France)

AbstractPassive acoustic recording (PAR) systems are non‐invasive and allow researchers to collect data over large spatial and/or temporal scales. As fish sounds are species‐specific and repetitive, PAR can provide a large amount of data about spatio‐temporal variation in fish distribution and behaviors. Ophidion rochei, found in the Mediterranean and Black Seas, is a sand‐dwelling species, meaning that the behavior of this cryptic nocturnal fish cannot be observed in the field. Fortunately, male O. rochei produce long, multiple‐pulsed calls that are easy to identify. The aim of this study was to determine whether or not male calls are linked to reproduction behaviors. If so, PAR would allow a detailed description of the seasonal and daily rhythms in O. rochei reproduction behavior. A hydrophone was deployed from 18 July 2011 to 21 June 2012 and from 7 June 2013 to 2 July 2013 on a sandy area (42°34′48′′ N, 8°43′43′′ E) in front of the STARESO research station (NW Corsica). Male sounds were obtained only at night from late spring to early fall. The annual sound production period corresponds to the reproductive season of O. rochei. Sound production followed diel cycles: it was sustained for the entire night at the beginning of the sound production season but limited to shorter periods in the evening during the second half of the season. These differences in daily and seasonal sound production tempo can be used in future recordings to make inter‐annual comparisons and estimate the physiological state of the fish.

A multi-year time series of marine mammal distribution in the Alaskan Arctic

The Marine Mammal Laboratory has deployed long-term, moored, passive acoustic recorders at numerous locations in the Alaskan Arctic since the BOEM-funded Chukchi Acoustics, Oceanography, and Zooplankton (CHAOZ) study began in 2010. These instruments, often collocated with oceanographic instruments, collect year-round passive acoustic data (16 kHz sampling rate, ~30% duty cycle). All acoustic recordings (100%) were analyzed using an in-house Matlab-based manual analysis program for 12 different Arctic and sub-Arctic cetacean and pinniped species, as well as for vessel, seismic airgun, and ice noise. Bowhead and beluga distributions showed similar patterns, with bimodal temporal distributions representing the fall and spring migrations. Infrequent gray whale detections (isolated on nearshore recorders) followed a similar, albeit less defined, bimodal distribution. Walrus and bearded seal calls were detected almost year-round, with peak bearded seal calling from April through June. Detections of sub-Arctic s...

Source level of fin whale calls from the Equatorial Pacific Ocean

Knowledge of source levels is essential for determining the range of effective fin whale communication and for estimating fin whale density from passive acoustic recordings. Source level calculations were performed on vocalizations automatically detected from spectrograms of Comprehensive Nuclear Test-Ban Treaty Organization data recorded at Wake Island in the Equatorial Pacific Ocean. Received levels were calculated, and transmission loss (TL) was determined using a season- specific OASIS Peregrine parabolic equation model for a 20 Hz signal. The model incorporated the location of the sensor in the deep sound channel, bathymetry of the area, and local sound speed profiles. TL was modeled for 360 bearings with a 1o resolution. TL values between the sensor and source were found for individual vocalizations using ranges and bearings calculated through hyperbolic localization. The exact whale depths were unknown but assumed to be 50 m. Over 7500 localizations of the fin whale 20 Hz call were identified from 2007 to 2009 with an average source level of 184.8 dB + /- 8.6 dB. When the 7500 calls were subsampled at 6 hour intervals to reduce the bias of loud, persistent singers, the average source level was 168.5 dB + /- 4.4 dB (n = 174). [Work supported by ONR.]

Studying deep diving odontocetes potential prey fields' densities and size structure in Hawaii using a DIDSON imaging sonar

Deep diving odontocetesodontocetes feed in the deep ocean on mesopelagic squid and fish. The distribution of these prey are poorly known but does affect the distribution of deep diving odontocete predators. Hence, it is important to collect data on the density and composition of potential prey to identify deep sea habitats that attract deep diving odontocetes. We used a DIDSON imaging sonar to investigate the density and size structure of mesopelagic animals along the Kona coast of Hawaii, where beaked, sperm and pilot whales are regularly seen. Data were collected at multiple stations during three research cruises by lowering the sonar in the water column to sample at different depths and monitoring the mesopelagic biomass with an EK60 38 kHz echosounder. Foraging activity of whales was monitored at few stations using passive acoustic recorders and a towed array of hydrophones. We were able to count and size 7068 pelagic animals. Density and size varied in space, with higher densities and bigger animals at the offshore stations. The DIDSON was effective at detecting targets bigger than 10 cm, a size range that includes potential prey of deep diving odontocetes. Preliminary data suggest differences may exists in habitat selection by each deep diving odontocetes.

A first look at the Ocean Noise Reference Station Network: The soundscape of Stellwagen Bank National Marine Sanctuary

In order to compare long-term changes and trends in soundscapes around the United States, a multi-year network of identical autonomous passive acoustic recording systems, the Ocean Noise Reference Station (NRS) Network, has been established. In partnership with the National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research, NOAA Pacific Marine Environmental Laboratory, NOAA National Marine Fisheries Service, NOAA Office of National Marine Sanctuaries, and the National Park Service, hydrophone moorings were deployed in 12 discrete soundscapes in the Northeast Pacific and Northwest Atlantic oceans to record underwater ambient sound levels in the 10 to 2200 Hz frequency range. This initial analysis utilized the first year of available data from the NRS deployed in Stellwagen Bank National Marine Sanctuary (SBNMS), a busy area for both natural and anthropogenic activity. Preliminary results indicate that: (1) broadband (10-2200 Hz) ambient sound levels at SBNMS are stable year round in association with constant vessel activity in the nearby shipping lane to Boston, MA, (2) surface wind speed is positively correlated with broadband noise levels, (3) intensity of low-frequency baleen whale calling activity varies seasonally, but signals are acoustically detectable year-round. Future analyses will compare the soundscapes of all 12 NRS sites.

Stereotyped, repetitive gunshot call patterns produced by the North Pacific right whale, Eubalaena japonica

The Marine Mammal Laboratory has deployed long-term passive acoustic recorders along the 50 m and 70 m isobaths throughout the Bering Sea since 2007. Instruments recorded at either 4 kHz on a ~7-11% duty cycle, or 8 kHz on a 30-45% duty cycle. In addition, directional sonobuoys were deployed during field surveys to allow real-time monitoring for large whale presence. During the 2010 survey, a stereotyped, repetitive gunshot call pattern was acoustically detected on sonobuoys. This same call pattern was then detected on two different long-term moored recorders in two separate years. Since then, six different stereotyped, repetitive patterns have been documented, three of which have been analyzed. Preliminary results show that each pattern has a minimum of 30 iterations repeated over several hours. Furthermore, in several cases, these patterns are repeated throughout the season, in consecutive years, and in one instance, in non-consecutive years. While male North Atlantic right whales produce long gunshot bouts similar to the reproductive advertisement known in other species, right whales are not known to produce any type of repeated stereotyped pattern. This represents the first study to document stereotyped repetitive gunshot patterning in right whales. [Work funded by the Bureau of Ocean Energy Management.]

Effects of anthropogenic noise on migrating bowhead whales in the Beaufort Sea

Greeneridge Sciences, Inc. (Greeneridge), has conducted multi-year, underwater, acoustic measurements at two study areas offshore of the North Slope of Alaska in the Beaufort Sea. The primary objective of these studies was to measure industrial sounds, e.g., those produced by oil production, seismic exploration, and drilling activities, and to assess their potential effects on the behavior of bowhead whales during their annual fall migration. To meet this objective, during open-water season every year from 2001 to 2016 (BP, Hilcorp) and 2007 to 2014 (Shell), Greeneridge deployed passive acoustic recorders equipped with directional sensors (DASARs) along the continental shelf. Over the course of these studies, millions of bowhead calls were localized, while ambient noise and various types of anthropogenic noise, such as tonal sounds associated with machinery and vessels and seismic airgun pulses, were quantified. The localization capabilities of the DASARs, large numbers of observations, and multi-year time series measurements together permitted, with high statistical power, quantitative evaluation of the effects of anthropogenic noise on bowhead behavior. Here, we’ll review some of our major findings, including the apparent displacement of calling bowhead whales and changes in their calling rate in response to industrial activities, consistency in their call source levels, and a shift in the frequency content of their call repertoire. [Work supported by BP Exploration Alaska, Shell Alaska Venture, and Hilcorp Alaska.]