Michael A. Thompson

Underwater components of humpback whale bubble-net feeding behaviour

Summary Humpback whales (Megaptera novaeangliae) employ a unique and complex foraging behaviour — bubble-netting — that involves expelling air underwater to form a vertical cylinder-ring of bubbles around prey. We used digital suction cup tags (DTAGs) that concurrently measure pitch, roll, heading, depth and sound (96 kHz sampling rate), to provide the first depiction of the underwater behaviours in which humpback whales engage during bubble-net feeding. Body mechanics and swim paths were analysed using custom visualization software that animates the underwater track of the whale and quantifies tag sensor values. Bubble production was identified aurally and through spectrographic analysis of tag audio records. We identified two classes of behaviour (upward-spiral; 6 animals, 118 events and double-loop; 3 animals, 182 events) that whales used to create bubble nets. Specifically, we show the actual swim path of the whales (e.g., number of revolutions, turning rate, depth interval of spiral), when and where in the process bubbles were expelled and the pattern of bubble expulsion used by the animals. Relative to other baleanopterids, bubble-netting humpbacks demonstrate increased manoeuvrability probably aided by a unique hydrodynamicly enhanced body form. We identified an approximately 20 m depth or depth interval limit to the use of bubble nets and suggest that this limit is due to the physics of bubble dispersal to which humpback whales have behaviourally adapted. All animals were feeding with at

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

Characterizing the relative contributions of large vessels to total ocean noise fields: a case study using the Gerry E. Studds Stellwagen Bank National Marine Sanctuary

Understanding and mitigating the effects of underwater noise on marine species requires substantial information regarding acoustic contributions from shipping. In 2006, we used the U.S. Coast Guards Automatic Identification System (AIS) to describe patterns of large commercial ship traffic within a U.S. National Marine Sanctuary. AIS data were combined with low‐frequency acoustic data from an array of nine‐ten autonomous recording units deployed throughout 2006. Analysis of received sound levels (10‐1000 Hz, root‐mean squared decibels re 1 μPascal ± standard error) averaged 119.5 ± 0.3 at high traffic locations. High traffic locations experienced double the acoustic power of less trafficked locations for the majority of the time period analyzed. Average source level estimates (71‐141 Hz, root‐mean squared decibels re 1 μPascal ± standard error) for individual vessels ranged from 158 ± 2 (research vessel) to 186 ± 2 (oil tanker). Tankers were estimated to contribute two times more acoustic power to the re...

Soundscapes and vocal behavior of humpback whales in Massachusetts Bay

In recent years, technological advances have revolutionized the study of acoustic communication in marine mammals. Exciting new perspectives on vocal behavior, acoustic habitats, and the influence of noise on communication are offered by passive acoustic monitoring (PAM) platforms such as acoustic tags (DTAGs), autonomous PAM recorders, drifting PAM buoys, and subsea gliders. These innovations bring the opportunity to integrate data from fixed and mobile PAM devices to gain deeper insight into the dynamic interactions between marine mammal vocalizations, behavioral context, and the acoustic environment. In this study, we bring together such data sources to study the vocal behavior and acoustic habitat of humpback whales in the context of their spring and summer feeding grounds. Recordings were made in Stellwagen Bank National Marine Sanctuary during 2008–2010, using arrays of autonomous PAM recorders and DTAGs. In addition, AIS ship-tracking data were obtained to study the influence of vessel movements. We present preliminary findings of this work and discuss future strategies for analyzing the spatiotemporal interactions between vocal behavior and acoustical context.