Denise Risch

Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away

The effect of underwater anthropogenic sound on marine mammals is of increasing concern. Here we show that humpback whale (Megaptera novaeangliae) song in the Stellwagen Bank National Marine Sanctuary (SBNMS) was reduced, concurrent with transmissions of an Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment approximately 200 km away. We detected the OAWRS experiment in SBNMS during an 11 day period in autumn 2006. We compared the occurrence of song for 11 days before, during and after the experiment with song over the same 33 calendar days in two later years. Using a quasi-Poisson generalized linear model (GLM), we demonstrate a significant difference in the number of minutes with detected song between periods and years. The lack of humpback whale song during the OAWRS experiment was the most substantial signal in the data. Our findings demonstrate the greatest published distance over which anthropogenic sound has been shown to affect vocalizing baleen whales, and the first time that active acoustic fisheries technology has been shown to have this effect. The suitability of Ocean Acoustic Waveguide Remote Sensing technology for in-situ, long term monitoring of marine ecosystems should be considered, bearing in mind its possible effects on non-target species, in particular protected species.

Seasonal migrations of North Atlantic minke whales: novel insights from large-scale passive acoustic monitoring networks

BackgroundLittle is known about migration patterns and seasonal distribution away from coastal summer feeding habitats of many pelagic baleen whales. Recently, large-scale passive acoustic monitoring networks have become available to explore migration patterns and identify critical habitats of these species. North Atlantic minke whales (Balaenoptera acutorostrata) perform seasonal migrations between high latitude summer feeding and low latitude winter breeding grounds. While the distribution and abundance of the species has been studied across their summer range, data on migration and winter habitat are virtually missing. Acoustic recordings, from 16 different sites from across the North Atlantic, were analyzed to examine the seasonal and geographic variation in minke whale pulse train occurrence, infer information about migration routes and timing, and to identify possible winter habitats.ResultsAcoustic detections show that minke whales leave their winter grounds south of 30° N from March through early April. On their southward migration in autumn, minke whales leave waters north of 40° N from mid-October through early November. In the western North Atlantic spring migrants appear to track the warmer waters of the Gulf Stream along the continental shelf, while whales travel farther offshore in autumn. Abundant detections were found off the southeastern US and the Caribbean during winter. Minke whale pulse trains showed evidence of geographic variation, with longer pulse trains recorded south of 40° N. Very few pulse trains were recorded during summer in any of the datasets.ConclusionThis study highlights the feasibility of using acoustic monitoring networks to explore migration patterns of pelagic marine mammals. Results confirm the presence of minke whales off the southeastern US and the Caribbean during winter months. The absence of pulse train detections during summer suggests either that minke whales switch their vocal behaviour at this time of year, are absent from available recording sites or that variation in signal structure influenced automated detection. Alternatively, if pulse trains are produced in a reproductive context by males, these data may indicate their absence from the selected recording sites. Evidence of geographic variation in pulse train duration suggests different behavioural functions or use of these calls at different latitudes.

Passive acoustic tracking of singing humpback whales (Megaptera novaeangliae) on a northwest Atlantic feeding ground.

Passive acoustic tracking provides an unobtrusive method of studying the movement of sound-producing animals in the marine environment where traditional tracking methods may be costly or infeasible. We used passive acoustic tracking to characterize the fine-scale movements of singing humpback whales (Megaptera novaeangliae) on a northwest Atlantic feeding ground. Male humpback whales produce complex songs, a phenomenon that is well documented in tropical regions during the winter breeding season, but also occurs at higher latitudes during other times of year. Acoustic recordings were made throughout 2009 using an array of autonomous recording units deployed in the Stellwagen Bank National Marine Sanctuary. Song was recorded during spring and fall, and individual singing whales were localized and tracked throughout the array using a correlation sum estimation method on the time-synchronized recordings. Tracks were constructed for forty-three song sessions, revealing a high level of variation in movement patterns in both the spring and fall seasons, ranging from slow meandering to faster directional movement. Tracks were 30 min to 8 h in duration, and singers traveled distances ranging from 0.9 to 20.1 km. Mean swimming speed was 2.06 km/h (SD 0.95). Patterns and rates of movement indicated that most singers were actively swimming. In one case, two singers were tracked simultaneously, revealing a potential acoustic interaction. Our results provide a first description of the movements of singers on a northwest Atlantic feeding ground, and demonstrate the utility of passive acoustic tracking for studying the fine-scale movements of cetaceans within the behavioral context of their calls. These methods have further applications for conservation and management purposes, particularly by enhancing our ability to estimate cetacean densities using passive acoustic monitoring.

Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.

Individual calling behaviour and movements of North Atlantic minke whales (Balaenoptera acutorostrata)

Information on individual calling behaviour and source levels are important for understanding acoustically mediated social interactions of marine mammals, for which visual observations are difficult to obtain. Our study, conducted in the Stellwagen Bank National Marine Sanctuary (SBNMS), located in the Gulf of Maine, USA, used passive acoustic arrays to track North Atlantic minke whales and assess the sound production behaviour of individuals. A total of 18 minke whales were acoustically tracked in this study. Individual calling rates were variable, with a median intercall interval (ICI) of 60.3 s. Average source levels (SLrms) for minke whales pulse trains ranged between 164 and 168 dB re 1 μPa, resulting in a minimum detection range of 0.4–10.2 km for these calls in this urban, coastal environment. All tracked animals were actively swimming at a speed of 5.0 ± 1.2 km/h, which matches swimming speeds of migrating minke whales from other areas and confirms SBNMS as part of the migration route of this species in the Western North Atlantic. Tracked minke whales produced 7 discrete call types belonging to 3 main categories, yet no individual produced all call types. Instead, minke whales produced 2 multisyllabic call sequences (A and B) by combining 3–4 different call types in a non-random order. While 7 of the tracked individuals produced calling pattern A, 10 whales used calling pattern B, and only 1 animal combined call types differently. Animals producing different call sequences were in acoustic range of one another on several occasions, suggesting they may use these sequences for mediating social interactions. The fact that the same calling patterns were shared by several individuals suggests that these patterns may contain information related to sex, age or behavioural context.

Management of acoustic metadata for bioacoustics

Abstract Recent expansion in the capabilities of passive acoustic monitoring of sound-producing animals is providing expansive data sets in many locations. These long-term data sets will allow the investigation of questions related to the ecology of sound-producing animals on time scales ranging from diel and seasonal to inter-annual and decadal. Analyses of these data often span multiple analysts from various research groups over several years of effort and, as a consequence, have begun to generate large amounts of scattered acoustic metadata. It has therefore become imperative to standardize the types of metadata being generated. A critical aspect of being able to learn from such large and varied acoustic data sets is providing consistent and transparent access that can enable the integration of various analysis efforts. This is juxtaposed with the need to include new information for specific research questions that evolve over time. Hence, a method is proposed for organizing acoustic metadata that addresses many of the problems associated with the retention of metadata from large passive acoustic data sets. A structure was developed for organizing acoustic metadata in a consistent manner, specifying required and optional terms to describe acoustic information derived from a recording. A client-server database was created to implement this data representation as a networked data service that can be accessed from several programming languages. Support for data import from a wide variety of sources such as spreadsheets and databases is provided. The implementation was extended to access Internet-available data products, permitting access to a variety of environmental information types (e.g. sea surface temperature, sunrise/sunset, etc.) from a wide range of sources as if they were part of the data service. This metadata service is in use at several institutions and has been used to track and analyze millions of acoustic detections from marine mammals, fish, elephants, and anthropogenic sound sources.

NEPAN: A U.S. Northeast Passive Acoustic Sensing Network for Monitoring, Reducing Threats and the Conservation of Marine Animals

I ncreasing anthropogenic activities in our oceans and their subsequent impacts onmarine ecosystems are clear conservation issues of national and global concern. Habitat degradation and the indirect impacts on marine vertebrates from activities associated with oil and gas exploration, renewable energy development, and shipping or fisheries operations threaten marine ecosystem health (Kappel, 2005; Halpern et al., 2007; Read, 2008; Davidson et al., 2012; Rolland et al., 2012). Efficient and cost-effective means to assess species distribution, abundance, and exposure to anthropogenic impacts are critical to the conservation of those species and their habitat. The mission of some federal agencies, such as National Oceanic and Atmospheric Administration (NOAA) in theUnited States, includes the conservation and recovery of depleted or endangered marine species, in accordance with the Marine Mammal Protection Act and the Endangered Species Act. Essential to these mandates is an adequate understanding of marine animal abundance, population trends, and seasonal occurrence, as well as an assessment of sources of risks associated with human activities. Among these risks are the effects of underwater noise introduced by human activities on marine animal acoustic communication, hearing and behavior, and the direct interactions of individual animals with fisheries and shipping operations (Cholewiak, Risch et al., 2013). Sound propagates more readily and over greater distances through water than light. Given this and the fact that light is limited at depth, sound is the primary modality of choice for marine animal communication, foraging, and navigation. Many marine species are highly vocal and much of their social, reproductive, and foraging behavior is acoustically mediated. Studies of the vocalizations that these animals emit—although completely reliant on the animals actually vocalizing—can provide information on their occurrence, distribution, relative abundance, and habitat use (e.g., Moore et al., 2006; Van Parijs et al., 2009; Širović & Hildebrand, 2011; Van Opzeeland et al., 2013a; Risch et al., 2014). In the past decade, passive acoustic approaches for studying marine animal populations have seen a rapid expansion in both the tools available and the geographic scope in which studies have been conducted. Substantial imMarch/A provements in the capabilities, availability, and price of acoustic recorders now provide a suite of cost-effective options for researchers to characterize the acoustic ecology of many species. They also provide means to quantify human-introduced noise levels in continuous records gathered in broad areas and over long periods. Recording devices include (a) fixed bottom-mounted acoustic recorders (BMARs) that can record up to several years in a single deployment, (b) hydrophone arrays towed behind survey vessels, (c) acoustic tags that record individual animal calls, (d) autonomous underwater vehicles (such as gliders) and unmanned surface vehicles (capable of navigating along assigned routes) or (e) anchored surface buoys that transmit underwater acoustic data to a land-based location in near real-time (Figure 1a). Hardware pril 2015 Volume 49 Number 2 71 and software refinements now allow data collection in remote areas and detection of species that are difficult to observe using aircraftor vesselbased visual surveys. Emerging theoretical methodologies applied to passive acoustic data provide novel ways to address largescale ecological and behavioral questions. For example, using acoustic indices tomonitor biodiversity and species richness (Fay, 2009; McWilliam & Hawkins, 2013; Staaterman et al., 2013; Staaterman & Paris, 2014), modeling loss of “communication space” (i.e., the space over which the sounds of an animal can be heard by conspecifics, or a listening animal can hear sounds of conspecifics) (Clark et al., 2009; Hatch et al., 2012; Williams et al., 2014), and integrating visual data with passively obtained acoustic data to increase the 72 Marine Technology Society Journa value of each technique (Thompson et al., 2014). Studies of marine mammals, especially cetaceans, have traditionally been conducted visually, from either vessel or aerial platforms. However, visual surveys are limited by daylight and weather conditions, as well as the short amount of time that marine mammals spend at the surface and are therefore detectable (e.g., Clark et al., 2010). Unconstrained by visual detection limitations, passive acoustic studies consistently provide a far richer characterization of marine mammal occurrence and habitat use information beyond seasons and regions where visual surveys previously documented them (e.g., Vu et al., 2012; Van Opzeeland et al., 2013b; Širović et al., 2014). Such passive acoustic studies highlight the need to transition to techniques that more completely characterize the actual disl tribution, occurrence, and relative abundance of marine mammals. Recent passive acoustic studies have also been used to identify spawning fish stocks, map their distribution, and define their seasonal occurrence and longterm persistence (Hernandez et al., 2013; Wall et al., 2012). Combined with active acoustic technology (i.e., in this case active acoustics refers to the high-frequency pinging sound produced by tags implanted in individual mature fish), which provides detailed information on behavior, movement patterns, sex ratios, and site fidelity of fish populations (Dean et al., 2012, 2014; Zemeckis et al., 2014a, 2014b, 2014c), this blended approach offers a novel direction for fisheries management and the conservation of fish stocks. Consequently, the use of passive acoustic methods to describe animal distribution, occurrence, abundance, and behavior is increasingly being recognized as tools not only for basic research but also with clear monitoring roles that substantially improve our capacity to inform conservation strategies. These are conservation and monitoring strategies that undoubtedly further the mission of NOAA and those of its partner agencies. NOAA’s Current Involvement in Passive Acoustic Research and Development Within NOAA, passive acoustic research has steadily grown in importance as a valued technique for improving and modernizing the collection of biological and anthropogenic data. NOAA Fisheries’ Offices of Science and Technology and Protected Resources and the National Ocean Service’s Office of National Marine Sanctuaries are currently finalizing an agency-wide Ocean Noise Strategy that aims to guide NOAA’s science FIGURE 1 (a) This image depicts the range of passive acoustic technologies currently available for collecting data. These include bottom-mounted archival marine acoustic recorders, acoustic recording tags deployed on animals, acoustic arrays towed behind survey vessels and autonomous underwater vehicles or gliders, as well as surface-mounted buoys that report back data in near real time. (b) This image depicts the possible “soundscape” of an ocean habitat composed of sound contributions from invertebrates, fish, marine mammals, weather events, and anthropogenic sources such as vessels. Long-term measurements of changes in soundscapes, such as the decrease in biological or increase in anthropogenic sound sources, will enable the relative “acoustic health” of a habitat to be monitored. and management decisions toward a longer-term vision for addressing noise impacts to marine life (http:// cetsound.noaa.gov). The Strategy highlights three major areas: (1) the importance of sound use and hearing for a diverse array of NOAA-managed species, (2) the importance of acoustic habi ta t in support ing NOAA ’ s management of these species, and (3) the data collection, tools, and approaches necessary to characterize soundscapes (e.g., Figure 1b) in order to support speciesand habitat-based management approaches. The Northeast Passive Acoustic Sensing Network (NEPAN) is a premier example of how to go about collecting data to inform the Strategy in a broad reaching manner. NOAA’s Northeast Regional Passive Acoustic Research At NOAA’s Northeast Fisheries Science Center (NEFSC), the Passive Acoustic Research Program’s primary focus is collecting passive acoustic data throughout the westernNorth Atlantic Ocean using a variety of the fixed and mobile platforms identified above. Our work—along with research partners at the Stellwagen Bank National Marine Sanctuary (SBNMS) and regular collaborative interactions withNationalMarine Fisheries Service (NMFS) science centers and headquarters and academia—combines long-term monitoring of marine species to understand their distribution, abundance and ecology, and quantification of anthropogenic noise threats with research focusing on monitoring the soundscapes of various key habitats in our region. Ultimately, our aim is to support broad marine management and conservation strategies throughout NOAA as part of a larger network of scientists conducting passive acoustic research. A Vision for a Comprehensive Passive Acoustic Sensing Network We envision a passive acoustic monitoring network positioned over the continental shelf and upper continental slope off the East Coast of the United States that will employ archival and near real-time passive acoustic systems to meet pressing NOAAmanagement needs. The network would include both fixed and mobile assets that could monitor marine mammals, soniferous fish and ocean noise over both short (days to weeks) and long (months to years) time scales. Some of these assets would be deployed in sensitive or industrial areas, such as wind farm construction sites, shipping lanes, heavily fished areas, or marine reserves, while others would cover broad spatial scales to inform questions about species ’ ranges, migration routes, or presence in unexpected locations. Ideally, some network assets would be collocated with oceanographic observatories (e.g., Northeast Regional Association of Coastal an

Long-term passive acoustic recordings track the changing distribution of North Atlantic right whales (Eubalaena glacialis) from 2004 to 2014

Given new distribution patterns of the endangered North Atlantic right whale (NARW; Eubalaena glacialis) population in recent years, an improved understanding of spatio-temporal movements are imperative for the conservation of this species. While so far visual data have provided most information on NARW movements, passive acoustic monitoring (PAM) was used in this study in order to better capture year-round NARW presence. This project used PAM data from 2004 to 2014 collected by 19 organizations throughout the western North Atlantic Ocean. Overall, data from 324 recorders (35,600 days) were processed and analyzed using a classification and detection system. Results highlight almost year-round habitat use of the western North Atlantic Ocean, with a decrease in detections in waters off Cape Hatteras, North Carolina in summer and fall. Data collected post 2010 showed an increased NARW presence in the mid-Atlantic region and a simultaneous decrease in the northern Gulf of Maine. In addition, NARWs were widely distributed across most regions throughout winter months. This study demonstrates that a large-scale analysis of PAM data provides significant value to understanding and tracking shifts in large whale movements over long time scales.

Tethys: A workbench for bioacoustic measurements and environmental data

A growing number of passive acoustic monitoring systems have resulted in a wealth of annotation information, or metadata, for recordings. These metadata are semi-structured. Some parameters are essentially mandatory (e.g., time of detection and what was detected) while others are highly dependent upon the question that a researcher is asking. Tethys is a metadata system for spatial-temporal acoustic data that provides structure where it is appropriate and flexibility where it is needed. Networked metadata are stored in an extended markup language (XML) database, and served to workstations over a network. The ability to export summary data to OBIS-SEAMAP is in development. The second purpose of Tethys is to serve as a scientific workbench. Interfaces are provided to networked databases, permitting the import of data from a wide variety of sources, such as lunar illumination or sea ice coverage. Interfaces currently exist for Matlab, Java, and Python. Writing data driven queries using a single interface ena...

Sonar signal analysis: Biological consequences of out-of-band acoustic signals from active sonar systems

Sonar signal analysis: Biological consequences of out-of-band acoustic signals from active sonar systems [conference presentation]