Rutenko, A.N., M.M. Zykov, V.A. Gritsenko, M. Yu. Fershalov, M.R. Jenkerson, D.S. Manulchev, R. Racca, and V.E. Nechayuk

Environmental Monitoring and Assessment 194 (Suppl 1): 744 (2022)

DOI: 10.1007/s10661-022-10021-y

During the summer of 2015, four 4D seismic surveys were conducted on the northeastern Sakhalin shelf near the feeding grounds of the Korean-Okhotsk (western) gray whale (Eschrichtius robustus) population. In addition to the seismic surveys, onshore pile driving activities and vessel operations occurred. Forty autonomous underwater acoustic recorders provided data in the 2 Hz to15 kHz frequency band. Recordings were analyzed to evaluate the characteristics of impulses propagating from the seismic sources. Acoustic metrics analyzed comprised peak sound pressure level (PK), mean square sound pressure level (SPL), sound exposure level (SEL), T100%, T90% (the time intervals that contain the full and 90% of the energy of the impulse), and kurtosis. The impulses analyzed differed significantly due to the variability and complexity of propagation in the shallow water of the northeast Sakhalin shelf. At larger ranges, a seismic precursor propagated in the seabed ahead of the acoustic impulse, and the impulses often interfered with each other, complicating analyses. Additional processing of recordings allowed evaluation and documentation of relevant metrics for pile driving, vessel sounds, and ambient background levels. The computed metrics were used to calibrate acoustic models, generating time resolved estimates of the acoustic levels from seismic surveys, pile driving, and vessel operations on a gray whale distribution grid and along observed gray whale tracks. This paper describes the development of the metrics and the calibrated acoustic models, both of which will be used in work quantifying gray whale behavioral and distribution responses to underwater sounds and to determine whether these observed responses have the potential to impact important parameters at the population level (e.g., reproductive success).

Gailey, G., M.M. Zykov, O. Sychenko, A. Rutenko, A.L. Blanchard, L.A.M. Aerts, and R.H. Melton

Environmental Monitoring and Assessment 194 (Suppl 1): 739 (2022)

DOI: 10.1007/s10661-022-10025-8

Oil and gas development off northeastern Sakhalin Island, Russia, has exposed the western gray whale population on their summer-fall foraging grounds to a range of anthropogenic activities, such as pile driving, dredging, pipeline installation, and seismic surveys. In 2015, the number of seismic surveys within a feeding season surpassed the level of the number and duration of previous seismic survey activities known to have occurred close to the gray whales’ feeding ground, with the potential to cause disturbance to their feeding activity. To examine the extent that gray whales were potentially avoiding areas when exposed to seismic and vessel sounds, shore-based teams monitored the abundance and distribution of gray whales from 13 stations that encompassed the known nearshore feeding area. Gray whale density was examined in relation to natural (spatial, temporal, and prey energy) and anthropogenic (cumulative sound exposure from vessel and seismic sounds) explanatory variables using Generalized Additive Models (GAM). Distance from shore, water depth, date, and northing explained a significant amount of variation in gray whale densities. Prey energy from crustaceans, specifically amphipods, isopods, and cumaceans also significantly influenced gray whale densities in the nearshore feeding area. Increasing cumulative exposure to vessel and seismic sounds resulted in both a short- and longer-term decline in gray whale density in an area. This study provides further insights about western gray whale responses to anthropogenic activity in proximity to and within the nearshore feeding area. As the frequency of seismic surveys and other non-oil and gas anthropogenic activity are expected to increase off Sakhalin Island, it is critical to continue to monitor and assess potential impacts on this endangered population of gray whales.

Rutenko, A.N., M.M. Zykov, V.A. Gritsenko, M.Y. Fershalov, M.R. Jenkerson, R. Racca, and V.E. Nechayuk

Environmental Monitoring and Assessment 194 (Suppl 1): 745 (2022)

DOI: 10.1007/s10661-022-10019-6

Exxon Neftegas Ltd. (ENL) carried out three 4D seismic surveys during the summer of 2015. Seismic operations in two of these fields (Odoptu and Chayvo) ensonified the nearshore feeding area of Korean-Okhotsk (western) gray whales (Eschrichtius robustus), potentially disturbing feeding activities. Following model-based optimization of the source design to minimize its lateral acoustic footprint, pre-season modeling was used to compute the acoustic exposure along each survey line. Real-time acoustic data facilitated implementation of mitigation measures aimed to minimize disturbance of whales. Acoustic data originated from underwater recorders deployed on the seafloor. Two complementary approaches were used to transmit recorded sound data to a computer housed at the Central Post (CP), where decisions regarding mitigation shut downs were made. In the first approach, a limited bandwidth (2–2000 Hz) sampling of the data was transmitted via cable to a surface buoy, which relayed these data to a shore station up to 15 km away via digital VHF telemetry. At the shore station, acoustic impulses from the seismic surveys were processed to compute impulse characteristics in the form of estimates of sound exposure level and peak sound pressure level, as well as one-minute-average 1/3-octave power spectral density coefficients, which were then transmitted to the CP via the internet. In the second, the pulse characteristics were computed through algorithms running on an onboard processor in each recorder’s surface buoy and sent directly to the CP computer via an Iridium satellite uplink. Both methods of data transfer proved viable, but Iridium transmission achieved the goal without the need for any shore based relay stations and is therefore more operationally efficient than VHF transmission. At the CP, analysts used the real-time acoustic data to calibrate and adjust the output of pre-season acoustical model runs. The acoustic footprint for the active seismic source, advancing synchronously with the motion of the seismic vessel and changing as the sound propagation environment changed, was computed from the calibrated and adjusted model output and integrated through the software Pythagoras with locations of gray whales provided by shore-based observers. This enabled analysts to require air gun array shutdowns before whales were exposed to mean square sound pressure levels greater than the behavioral response threshold of 163 dB re 1 μPa^2. The method described here provides a realistic means of mitigating the possible effects of air guns at a behavioral response level, whereas most seismic surveys rely on pre-established mitigation radii to manage the risk of injury to a whale.

Aerts, L.A.M., M.R. Jenkerson, V.E. Nechayuk, G. Gailey, R. Racca, A.L. Blanchard, L.K. Schwarz, and H.R. Melton

Environmental Monitoring and Assessment 194 (Suppl 1): 746 (2022)

DOI: 10.1007/s10661-022-10016-9

In 2015, two oil and gas companies conducted seismic surveys along the northeast coast of Sakhalin Island, Russia, near western gray whale (Eschrichtius robustus) feeding areas. This population of whales was listed as Critically Endangered at the time of the operations described here but has been reclassified as Endangered since 2018. The number and duration of the 2015 seismic surveys surpassed the level of previous seismic survey activity in this area, elevating concerns regarding disturbance of feeding gray whales and the potential for auditory injury. Exxon Neftegas Limited (ENL) developed a mitigation approach to address these concerns and, more importantly, implemented a comprehensive data collection strategy to assess the effectiveness of this approach. The mitigation approach prioritized completion of the seismic surveys closest to the nearshore feeding area as early in the season as possible, when fewer gray whales would be present. This was accomplished by increasing operational efficiency through the use of multiple seismic vessels and by establishing zones with specific seasonal criteria determining when air gun shutdowns would be implemented. These zones and seasonal criteria were based on pre-season modeled acoustic footprints of the air gun array and on gray whale distribution data collected over the previous 10 years. Real-time acoustic and whale sighting data were instrumental in the implementation of air gun shutdowns. The mitigation effectiveness of these shutdowns was assessed through analyzing short-term behavioral responses and shifts in gray whale distribution due to sound exposure. The overall mitigation strategy of an early survey completion was assessed through bioenergetics models that predict how reduced foraging activity might affect gray whale reproduction and maternal survival. This assessment relied on a total of 17 shore-based and 5 vessel-based teams collecting behavior, distribution, photo-identification, prey, and acoustic data. This paper describes the mitigation approach, the implementation of mitigation measures using real-time acoustic and gray whale location data, and the strategy to assess impacts and mitigation effectiveness.

Gailey, G., O. Sychenko, M.M. Zykov, A. Rutenko, A. Blanchard, and R.H. Melton

Environmental Monitoring and Assessment 194 (Suppl 1): 740 (2022)

DOI: 10.1007/s10661-022-10023-w

Gray whales utilizing their foraging grounds off northeastern Sakhalin Island, Russia, have been increasingly exposed to anthropogenic activities related to oil and gas development over the past two decades. In 2015, four seismic vessels, contracted by two operators, conducted surveys near and within the gray whale feeding grounds. Mitigation and monitoring plans were developed prior to the survey and implemented in the field, with real-time data transfers to assist the implementation of measures aimed at minimizing impacts of acoustic exposure. This study examined the behavioral response of gray whales relative to vessel proximities and sounds generated during seismic exploration. Five shore-based teams monitored gray whale behavior from 1 June to 30 September using theodolite tracking and focal follow methodologies. Behavioral data were combined with acoustic and benthic information from studies conducted during the same period. A total of 1270 tracks (mean duration = 0.9 h) and 401 focal follows (1.1 h) were collected with gray whales exposed to sounds ranging from 59 to 172 dB re 1 μPa^2 SPL. Mixed models were used to examine 13 movement and 10 respiration response variables relative to “natural,” acoustic, and non-acoustic explanatory variables. Water depth and behavioral state were the largest predictors of gray whale movement and respiration patterns. As vessels approached whales with increasing seismic/vessel sound exposure levels and decreasing distances, several gray whale movement and respiration response variables significantly changed (increasing speed, directionality, surface time, respiration intervals, etc.). Although the mitigation measures employed could have reduced larger/long-term responses and sensitization to the seismic activities, this study illustrates that mitigation measures did not eliminate behavioral responses, at least in the short-term, of feeding gray whales to the activities.

Kowarski, K., S. Cerchio, H. Whitehead, D. Cholewiak, and H. Moors-Murphy

Bioacoustics (Advance Online Publication)

DOI: 10.1080/09524622.2022.2122561

The use of song as a reproductive display is common in the animal kingdom; however, for many taxa, little is known of song ontogeny. Male humpback whales produce elaborate songs on low latitude breeding grounds in winter and begin to sing on high latitude feeding grounds in late summer, yet songs from the two locations are rarely compared. Seasonal song ontogeny in western North Atlantic humpback whales was explored by comparing songs recorded in high latitude feeding grounds (Canada in spring 2016 and fall 2016 to winter 2017) with songs recorded in a low latitude breeding ground (Dominican Republic in winter and spring 2017). High-quality song samples were selected, and every phrase annotated. Song theme order, song duration, and number of phrase repetitions were compared across samples. The most variability in theme order was found between November and December in the Canadian recordings, a phase in song ontogeny that may be important for learning. Song duration gradually increased, via an increase in phrase repetitions, through the breeding season, before peaking in the Dominican Republic between January and March. A comparison to oscine bird seasonal song ontogeny revealed many similarities, highlighting potentially similar physiological processes between humpback whales and songbirds.

Miksis-Olds, J.L., B.S. Martin, K. Lowell, C. Verlinden, and K.D. Heaney

JASA Express Letters 2: 090801 (2022)

DOI: 10.1121/10.0013999

Using a 2-year time series (2019–2020) of 1-min sound pressure level averages from seven sites, the extension of COVID-related quieting documented in coastal soundscapes to deep (approximately 200–900 m) waters off the southeastern United States was assessed. Sites ranged in distance to the continental shelf break and shipping lanes. Sound level decreases in 2020 were observed at sites closest to the shelf break and shipping lanes but were inconsistent with the timing of shipping changes related to a COVID-19 slowdown. These observations are consistent with increased numbers of vessel tracks in 2020 compared to 2019 at a majority of sites.

MacGillivray, A.O., L.M. Ainsworth, J. Zhao, J.N. Dolman, D.E. Hannay, H. Frouin-Mouy, K.B. Trounce, and D.A. White

Journal of the Acoustical Society of America 152: 1547-1563 (2022)

DOI: 10.1121/10.0013747

Measurements of the source levels of 9880 passes of 3188 different large commercial ships from the Enhancing Cetacean Habitat and Observation (ECHO) program database were used to investigate the dependencies of vessel underwater noise emissions on several vessel design parameters and operating conditions. Trends in the dataset were analyzed using functional regression analysis, which is an extension of standard regression analysis and represents a response variable (decidecade band source level) as a continuous function of a predictor variable (frequency). The statistical model was applied to source level data for six vessel categories: cruise ships, container ships, bulk carriers, tankers, tugs, and vehicle carriers. Depending on the frequency band and category, the functional regression model explained approximately 25%–50% of the variance in the ECHO dataset. The two main operational parameters, speed through water and actual draft, were the predictors most strongly correlated with source levels in all of the vessel categories. Vessel size (represented via length overall) was the design parameter with the strongest correlation to underwater radiated noise for three categories of vessels (bulkers, containers, and tankers). Other design parameters that were investigated (engine revolutions per minute, engine power, design speed.

Kowarski, K.A., S.B. Martin, E.E. Maxner, C.B. Lawrence, J.J.-Y. Delarue, and J.L. Miksis-Olds

Marine Mammal Science (Advanced Online Publication)

DOI: 10.1111/mms.12962

Long-term distribution data for cetaceans are lacking, inhibiting the ability of management bodies to assess trends and react appropriately. Such is true even along the US Atlantic Outer Continental Shelf (OCS) where previous passive acoustic monitoring programs have laid the groundwork for monitoring cetacean occurrence over a multidecadal scale. Here, we continue and expand the scope of previous acoustic programs, providing a synopsis of the monthly cetacean acoustic occurrence from late 2017 to late 2020. Acoustic data were collected using bottom-mounted autonomous recorders located at seven stations along the OCS in depths of 212–900 m. Automated cetacean vocalization detector-classifiers were applied, and the resulting automated detections directed the manual review of a subset of the data by analysts. Only manual detections informed the occurrence results. Six baleen whale species and at least eight toothed whale species occurred in the region with diversity increasing in winter. In considering previous monitoring program results, we found evidence that some mysticete whales are spending less time in the region annually, confirmed that some species occur farther offshore than previously reported, and identified two previously unreported areas utilized by beaked whales. For effective species management, these findings must be considered, and monitoring programs continued.

van der Knaap, I., E. Ashe, D. Hannay, A.G. Bergman, K.A. Nielsen, C.F. Lo, and R. Williams

Marine Pollution Bulletin 174: 113257 (2022)

DOI: 10.1016/j.marpolbul.2021.113257

There is growing concern about impacts of ship and small boat noise on marine wildlife. Few studies have quantified impacts of anthropogenic noise on ecologically, economically, and culturally important fish. We conducted open net pen experiments to measure Pacific herring (Clupea pallasii) and juvenile salmon (pink, Oncorhynchus gorbuscha, and chum, Oncorhynchus keta) behavioural response to noise generated by three boats travelling at different speeds. Dose-response curves for herring and salmon estimated 50% probability of eliciting a response at broadband received levels of 123 and 140 dB (re 1 μPa), respectively. Composite responses (yes/no behaviour change) were evaluated. Both genera spent more time exhibiting behaviours consistent with anti-predator response during boat passings. Repeated elicitation of vigilance or anti-predatory responses could result in increased energy expenditure or decreased foraging. These experiments form an important step toward assessing population-level consequences of noise, and its ecological costs and benefits to predators and prey.

Letessier, T.B., J. Johnston, J. Delarue, B. Martin, and R.C. Anderson

Journal of Zoology (Advanced Online Publication)

DOI: 10.1111/jzo.13000

Mobile predators serve important ecological functions, including acting as nutrient vectors between different ecosystems. In coral reefs, pelagic nutrient subsidies are believed to play an increasingly important role under ongoing and projected environmental changes. Here, we combine visual sightings with passive acoustic monitoring to report habitat use and behaviour by cetaceans within atoll lagoons in the Maldives and Chagos archipelagoes. We demonstrate that spinner dolphins (Stenella longirostris) are the most widely distributed and numerically abundant cetacean inside these atolls (>90% of all individual cetaceans by numbers). Our visual and acoustic observations both provide evidence of a regular diurnal behaviour, where dolphins enter the lagoons during the morning, for day-time resting, and exit during the afternoon, for night-time foraging offshore. Using standard metabolic models and timing of lagoonal residencies, we estimate that a dolphin pod would deposit approximately 288 ± 17 kg/year of nitrogen of primarily mesopelagic origin inside the lagoons. The nitrogen deposited inside an atoll lagoon by a dolphin pod resident year-round will therefore likely enhance coral reef productivity and resilience and suggests that these dolphins play a role in making pelagic energy and nutrients available to coral reefs. The absence of any acoustic detections following the reversal of the monsoon winds suggests that the short-to-medium-term residency of the dolphins is sensitive to seasonal productivity dynamics.

Delarue, J.-Y., H. Moors-Murphy, K.A. Kowarski, G.E. Davis, I.R. Urazghildiiev, and S.B. Martin

Endangered Species Research 47: 265-289 (2022)

DOI: 10.3354/esr01176

Six baleen whale species occur off eastern Canada, but little is known of their year-round occurrence across this large region. This complicates identifying areas that are important to them and may require critical habitat designation, especially for those species considered at risk. This is particularly true between fall and spring because of a lack of visual survey effort. The main objective of this paper is to provide a year-round and pluriannual description of the minimum acoustic occurrence of baleen whales, particularly blue Balaenoptera musculus, fin B. physalus, and humpback whales Megaptera novaeangliae. We deployed 25 acoustic recorders off eastern Canada between May 2015 and November 2017, and the data were analyzed using a combination of automated detectors and manual validation to identify vocalizations produced by these species. Blue, fin, and humpback whales occurred off eastern Canada year-round, a finding which contrasts the traditional seasonal latitude migration narrative for these species. The Scotian Shelf region and Flemish Pass-Orphan Basin areas seem particularly important for these animals and should be the focus of future research. Sei B. borealis, minke B. acutorostrata, and North Atlantic right whale Eubalaena glacialis vocalizations also occurred in the data but were not adequately captured by the adopted methodology. Coarse patterns of occurrence are presented for these species as a foundation for more detailed analyses. This study is the first to cover eastern Canadian waters for an extended continuous period and provides a baseline against which future changes can be assessed.

Shabangu, F.W. and K.A. Kowarski

Frontiers in Marine Science 9: 827324 (2022)

DOI: 10.3389/fmars.2022.827324

Little is known of the movements and seasonal occurrence of humpback whales (Megaptera novaeangliae) of South Africa and the Antarctic, populations once brought to near extinction by historic commercial whaling. We investigated the seasonal occurrence and diel-vocalizing pattern of humpback whale songs off the west coast of South Africa (migration route and opportunistic feeding ground) and the Maud Rise, Antarctica (feeding ground), using passive acoustic monitoring data collected between early 2014 and early 2017. Data were collected using acoustic autonomous recorders deployed 200-300 m below the sea surface in waters 855, 1,118 and 4,400 m deep. Acoustic data were manually analyzed for humpback whale vocalizations. While non-song calls were never identified, humpback whale songs were detected from June through December in South African waters, with a peak in percentage of acoustic occurrence around September/October in the austral spring. In Antarctic waters, songs were detected from March through May and in July (with a peak occurrence in April) where acoustic occurrence of humpback whales was negatively correlated to distance to the sea ice extent. Humpback whales were more vocally active at night than in the day at all recording sites. Detection range modelling indicates that humpback whale vocalizations could be detected as far as 18 and 45 km from recorders in South African and Antarctic waters, respectively. This study provides a multi-year description of the offshore acoustic occurrence of humpback whales off the west coast of South Africa and Maud Rise, Antarctica, regions that should continue to be monitored to understand these recovering populations.

Sweeney, S.O, J.M. Terhune, H. Frouin-Mouy, and P.A. Rouget

Journal of the Acoustical Society of America 151: 2310-2325 (2022)

DOI: 10.1121/10.0009956

Shipping is increasing in Arctic regions, exposing marine mammals to increased underwater noise. Noise analyses often use unweighted broadband sound pressure levels (SPL) to assess noise impacts, but this does not account for the animals' hearing abilities at different frequencies. In 2018 and 2019, noise levels were recorded at five and three sites, respectively, along a shipping route in an inlet of Northern Baffin Island, Canada. Broadband SPLs (10 Hz–25 kHz), unweighted and with auditory weighing functions from three marine mammal groups, were compared between times ore carriers (travelling < 9 knots) were present or absent. Clearly audible distances of shipping noise and exposure durations were estimated for each weighting function relative to vessel direction, orientation, and year. Auditory weighting functions had significant effects on the potential perception of shipping noise. Bowhead whales (Balaena mysticetus) experienced similar SPLs to unweighted levels. Narwhals (Monodon monoceros) and ringed seals (Pusa hispida) experienced lower SPLs. Narwhals were unlikely to clearly perceive shipping noise unless ships were in close proximity (<3 km) and ambient noise levels were low. Detectability propagation models of presumed noise exposure from shipping must be based on the hearing sensitivities of each species group when assessing noise impacts on marine mammals.

Stanistreet, J.E., W.A.M. Beslin, K. Kowarski, S.B. Martin, A. Westell, and H.B. Moors-Murphy

Scientific Reports 12(1): 1973 (2022)

DOI: 10.1038/s41598-022-05930-4

Experimental research has shown that beaked whales exhibit strong avoidance reactions to naval active sonars used during antisubmarine warfare training exercises, including cessation of echolocation and foraging activity. Behavioural responses to sonar have also been linked to strandings and mortality. Much of the research on the responses of beaked whales and other cetaceans to naval active sonar has occurred on or near U.S. naval training ranges, and the impacts of sonar in other regions remain poorly understood, particularly as these impacts, including mortality, are likely to go unobserved in offshore areas. In September 2016 the multinational naval exercise ‘CUTLASS FURY 2016’ (CF16) was conducted off eastern Canada. We used passive acoustic recordings collected in the region to quantify the occurrence and characteristics of sonar signals, measure ambient noise levels, and assess changes in the acoustic activity of beaked and sperm whales. The number of hours per day with echolocation clicks from Cuvier’s beaked whales and sperm whales were significantly reduced during CF16, compared to the pre-exercise period in 2016 (sperm whales) and to control data from 2015 (both species). Clicks from an unidentified Mesoplodont beaked whale species, sporadically detected prior to CF16, were absent during the exercise and for 7 days afterward. These results suggest that beaked and sperm whales ceased foraging in the vicinity of CF16 and likely avoided the affected area. Such disturbance may have energetic, health, and fitness consequences.

Popper, A.N. L. Hice-Dunton, E. Jenkins, D.M. Higgs, J. Krebs, A. Mooney, A. Rice, L. Roberts, F. Thomsen, K. Vigness-Raposa, D. Zeddies, and K.A. Williams

J. Acoust. Soc. Am. 151: 205–215 (2022)

DOI: 10.1121/10.0009237

There are substantial knowledge gaps regarding both the bioacoustics and the responses of animals to sounds associated with pre-construction, construction, and operations of offshore wind (OSW) energy development. A workgroup of the 2020 State of the Science Workshop on Wildlife and Offshore Wind Energy identified studies for the next five years to help stakeholders better understand potential cumulative biological impacts of sound and vibration to fishes and aquatic invertebrates as the OSW industry develops. The workgroup identified seven short-term priorities that include a mix of primary research and coordination efforts. Key research needs include the examination of animal displacement and other behavioral responses to sound, as well as hearing sensitivity studies related to particle motion, substrate vibration, and sound pressure. Other needs include: identification of priority taxa on which to focus research; standardization of methods; development of a long-term highly instrumented field site; and examination of sound mitigation options for fishes and aquatic invertebrates. Effective assessment of potential cumulative impacts of sound and vibration on fishes and aquatic invertebrates is currently precluded by these and other knowledge gaps. However, filling critical gaps in knowledge will improve our understanding of possible sound-related impacts of OSW energy development to populations and ecosystems.

Ainslie, M.A., S.B. Martin, K.B. Trounce, D.E. Hannay, J.M. Eickmeier, T.J. Deveau, K. Lucke, A.O. MacGillivray, V. Nolet, and P. Borys

Marine Pollution Bulletin 174: 113124 (2022)

DOI: 10.1016/j.marpolbul.2021.113124

The habitat of the endangered southern resident killer whale (SRKW) overlaps major international shipping lanes near the Port of Vancouver, British Columbia. Shipping is a dominant source of underwater noise, which can hinder SRKW key life functions. To reduce environmental pressure on the SRKWs, Vancouver Fraser Port Authority offers incentives for quieter ships. However, the absence of a widely accepted underwater radiated noise (URN) measurement procedure hinders the determination of relative quietness. We review URN measurement procedures, summarizing results to date from two Canadian-led projects aimed at improving harmonization of shallow-water URN measurement procedures: One supports the International Organization for Standardization (ISO) in the development of a URN measurement standard; the other supports the alignment of URN measurement procedures developed by ship classification societies. Weaknesses in conventional shallow-water URN metrics are identified, and two alternative metrics proposed. Optimal shallow-water measurement geometry is identified.

Ainslie, M.A., M.B. Halvorsen, and S.P. Robinson

IEEE J. Ocean. Eng. 47: 179-200 (2022)

DOI: 10.1109/JOE.2021.3085947

Applications of underwater acoustics include sonar, communication, geophysical imaging, acoustical oceanography, and bioacoustics. Specialists typically work with little interdisciplinary interaction, and the terminology they employ has evolved separately in each discipline, to the point that transdisciplinary misunderstandings are common. Furthermore, increasing societal concern about possible detrimental effects of underwater noise on aquatic animals has led national and international regulators to require monitoring of underwater noise, with a consequent need for interdisciplinary harmonization of terminology. By adopting a common language, we facilitate the effective communication of concepts and information in underwater acoustics, whether for research, technology, or regulation. In the words of William H. Taft, “Don’t write so that you can be understood, write so that you can’t be misunderstood.” Clear definitions of widely used terms are needed, such as those used for the characterization of sound fields (e.g., “soundscape” and “ambient noise”), sound sources (“source level” and “source waveform”), sound propagation (“transmission loss” and “propagation loss”), and sound reception (“hearing threshold” and “frequency weighting function”). Terms that are used synonymously in one application have different meanings in another (examples include “hearing threshold” versus “detection threshold” and “transmission loss” versus “propagation loss”). Distinct definitions for these and many other acoustic terms are provided in a standard published in April 2017 by the International Organization for Standardization, ISO 18405. This article summarizes ISO 18405 and the process that led to the published definitions, including the reasons for omitting some terms.

Kowarski, K., S. Cerchio, H. Whitehead, and H. Moors-Murphy

Bioacoustics 31: 450-469 (2022)

DOI: 10.1080/09524622.2021.1972838

At the onset of the winter breeding season, male humpback whales begin a prominent breeding behaviour, singing. Early songs are produced on summer feeding grounds prior to migration, but little is known about the proximate cues for the initiation of this behaviour, nor where or when it begins. We document the phenology of humpback whale singing along the western North Atlantic coast ranging from Newfoundland and Labrador, Canada to Massachusetts, USA through the fall-winter of 2015-16 (seven stations) and 2016-17 (three stations). Acoustic data from static recorders were categorised as containing humpback whale non-song calls, song fragments, or full songs. First heard in September, singing occurred throughout the fall-winter, but was not regular until October. Latitude, temperature, photoperiod, sea surface pressure, and wind speed were considered as potential explanatory variables for four definitions of song onset using forward stepwise regression. Final models included the environmental variables with photoperiod negatively correlated to singing (coefficient = −657; p-value = 0.04). Reliable environmental cues, such as photoperiod, may produce a heritable physiological response, resulting in whales acquiring the capacity and motivation to sing, with the subsequent timing and nature of song production influenced by other factors.

MacGillivray, A. and C. de Jong

J. Mar. Sci. Eng. 9: 369 (2021)

DOI: 10.3390/jmse/9040369

Underwater sound mapping is increasingly being used as a tool for monitoring and managing noise pollution from shipping in the marine environment. Sound maps typically rely on tracking data from the Automated Information System (AIS), but information available from AIS is limited and not easily related to vessel noise emissions. Thus, robust sound mapping tools not only require accurate models for estimating source levels for large numbers of marine vessels, but also an objective assessment of their uncertainties. As part of the Joint Monitoring Programme for Ambient Noise in the North Sea (JOMOPANS) project, a widely used reference spectrum model (RANDI 3.1) was validated against statistics of monopole ship source level measurements from the Vancouver Fraser Port Authority-led Enhancing Cetacean Habitat and Observation (ECHO) Program. These validation comparisons resulted in a new reference spectrum model (the JOMOPANS-ECHO source level model) that retains the power-law dependence on speed and length but incorporates class-specific reference speeds and new spectrum coefficients. The new reference spectrum model calculates the ship source level spectrum, in decidecade bands, as a function of frequency, speed, length, and AIS ship type. The statistical uncertainty (standard deviation of the deviation between model and measurement) in the predicted source level spectra of the new model is estimated to be 6 dB.

Kowarski, K.A., J.J.-Y. Delarue, B.J. Gaudet, and S.B. Martin

JASA Express Letters 1: 051201 (2021)

DOI: 10.1121/10.0004851

Passive acoustic monitoring (PAM) can inform wildlife management by providing information on the distribution of cetaceans. This paper presents an automatic data selection for validation (ADSV) method to effectively identify all species acoustically present in large PAM data sets. The ADSV method involves the application of automated detectors, the automated selection of a portion of data for manual review, and the evaluation/optimization of automated detectors. Using an exemplar data set, results from the ADSV method were compared to a more intensive systematic manual review method. The two methods were found to have similar species occurrence results (hourly occurrence matching 73%–100%).

Insley, S.J., W.D. Halliday, X. Mouy, and N. Diogou

R. Soc. Open Sci. 8: 202268 (2021)

DOI: 10.1098/rsos.202268

The bowhead whale is the only baleen whale endemic to the Arctic and is well adapted to this environment. Bowheads live near the polar ice edge for much of the year and although sea ice dynamics are not the only driver of their annual migratory movements, it likely plays a key role. Given the intrinsic variability of open water and ice, one might expect bowhead migratory plasticity to be high and linked to this proximate environmental factor. Here, through a network of underwater passive acoustic recorders, we document the first known occurrence of bowheads overwintering in what is normally their summer foraging grounds in the Amundsen Gulf and eastern Beaufort Sea. The underlying question is whether this is the leading edge of a phenological shift in a species' migratory behaviour in an environment undergoing dramatic shifts due to climate change.

Prior, M.K., M.A. Ainslie, M.B. Halvorsen, I. Hartstra, R.M. Laws, A.O. MacGillivray, R. Müller, S. Robinson, and L. Wang

J. Acoust. Soc. Am. 150: 3675-3692 (2021)

DOI: 10.1121/10.0006751

The acoustical output of marine-seismic airguns is determined from recordings of the sound pressure made on hydrophones suspended below a floating barge from which the airguns are also deployed. The signals from multiple types of airguns are considered and each type is operated over a range of deployment depths and chamber pressures. The acoustical output is characterized in terms of a “source waveform” with dimensions of the pressure-times-distance and in an infinite idealized medium, could be divided by the source-receiver distance to give the sound pressure at that receiver. In more realistic environments, the source waveform may be used to predict the pressure at any arbitrary receiver position simply by the application of a time-domain transfer function describing the propagation between the source and receiver. The sources are further characterized by metrics such as the peak source waveform and energy source level. These metrics are calculated in several frequency bands so that the resulting metrics can be used to characterize the acoustical output of the airguns in terms of their utility for seismic image-processing or possible effects on marine life. These characterizations provide reference data for the calibration of models that predict the airguns' acoustical output. They are validated via comparisons of the acoustic pressure measured on far-field hydrophones and predicted using the source waveforms. Comparisons are also made between empirically derived expressions relating the acoustic metrics to the chamber volume, chamber pressure, and deployment depth and similar expressions from the literature.

van der Knaap, I., J. Reubens, L. Thomas, M.A. Ainslie, H.V. Winter, J. Hubert, B. Martin, and H. Slabbekoorn

Current Biology 31(7): 1555-1562 (2021)

DOI: 10.1016/j.cub.2021.01.050

Geophysical exploration of the seabed is typically done through seismic surveys, using airgun arrays that produce intense, low-frequency-sound pulses that can be heard over hundreds of square kilometers, 24/7. Little is known about the effects of these sounds on free-ranging fish behavior. Effects reported range from subtle individual change in activity and swimming depth for captive fish to potential avoidance and changes in swimming velocity and diurnal activity patterns for free-swimming animals. However, the extent and duration of behavioral responses to seismic surveys remain largely unexplored for most fish species. In this study, we investigated the effect of a full-scale seismic survey on the movement behavior of free-swimming Atlantic cod (Gadus morhua). We found that cod did not leave the detection area more than expected during the experimental survey but that they left more quickly from 2 days to 2 weeks after the survey. Furthermore, during the exposure, cod decreased their activity, with time spent being “locally active” (moving small distances, showing high body acceleration) becoming shorter, and time spent being “inactive” (moving small distances, having low body acceleration) becoming longer. Additionally, diurnal activity cycles were disrupted with lower locally active peaks at dusk and dawn, periods when cod are known to actively feed. The combined effects of delayed deterrence and activity disruption indicate the potential for seismic surveys to affect energy budgets and to ultimately lead to population-level consequences.

Martin, S.B., B.J. Gaudet, H. Klinck, P.J. Dugan, J.L. Miksis-Olds, D.K. Mellinger, D.A. Mann, O. Boebel, C.C. Wilson, D.W. Ponirakis, and H. Moors-Murphy

JASA Express Letters 1(1): 011203 (2021)

DOI: 10.1121/10.0003324

This Letter proposes a frequency scaling for processing, storing, and sharing high-bandwidth, passive acoustic spectral data that optimizes data volume while maintaining reasonable data resolution. The format is a hybrid that uses 1 Hz resolution up to 455 Hz and millidecade frequency bands above 455 Hz. This hybrid is appropriate for many types of soundscape analysis, including detecting different types of soundscapes and regulatory applications like computing weighted sound exposure levels. Hybrid millidecade files are compressed compared to the 1 Hz equivalent such that one research center could feasibly store data from hundreds of projects for sharing among researchers globally.

Frouin-Mouy, H. and M.O. Hammill

J. Acoust. Soc. Am. 150: 281–293 (2021)

DOI: 10.1121/10.0005478

The hooded seal is a migratory species inhabiting the North Atlantic. Passive acoustic monitoring (PAM) conducted over spatial scales consistent with their known and potential habitat could provide insight into seasonal and spatial occurrence patterns of this species. Hooded seal airborne and underwater acoustic signals were recorded during the breeding season on the pack ice in the Gulf of St. Lawrence in March 2018 to better characterize their acoustic repertoire (notably underwater calls). In-air and underwater signals were classified into 12 and 22 types, respectively. Signals produced by males through the inflation and deflation of the proboscis and septum were the predominant sounds heard on the ice surface. Five of the 22 underwater signals were proboscis and septum noises. The remaining underwater signals (17) were categorized as voiced calls and further analyzed using two classification methods. Agreement with the initial subjective classification of voiced calls was high (77% for classification tree analysis and 88% for random forest analysis), showing that 12–13 call types separated well. The hooded seal's underwater acoustic repertoire is larger and more diverse than has been previously described. This study provides important baseline information necessary to monitor hooded seals using PAM.

McIntyre, D., W. Lee, H. Frouin-Mouy, D. Hannay, and P. Oshkai

Ocean Engineering 232: 109075 (2021)

DOI: j.oceaneng.2021.109075

Underwater radiated noise from marine ships represents the largest source of anthropogenic noise in oceans the world over, representing a substantial and persistent stressor to the health of marine ecosystems. The radiated noise from vessels can often be related to their velocity, and slowing vessels in critical habitat areas has been shown to reduce the average level of ambient noise in those regions; however, universal speed limits ignore the significant variation in speed-noise behaviour between vessels. We investigated the underwater radiated noise signatures and levels from eight coastal ferry vessels each operating at a range of speeds in order to examine the underlying causes of the atypical speed-noise correlations. The analysis revealed discrete patterns associated with speed ranges, suggesting that the increase in noise radiated at low velocities that was observed from some vessels was the result of a change in the regime of the physical mechanism generating the sound. Propeller-induced cavitation is the strongest possible explanation for noise of this type. The present results suggest that controllable-pitch propellers may be susceptible to changes in cavitation regimes resulting in increased radiated noise when operated under reduced loads, a finding that corroborates previous model-scale experimental evidence of the same behaviour.

Urazghildiiev, I.R. and D.E. Hannay

IEEE J. Ocean. Eng. 46: 1302-1312 (2021)

DOI: 10.1109/JOE.2021.3082758

The problem of passive acoustic estimating the position of a source using a network of synchronized underwater compact arrays is considered. Maximum-likelihood estimators using angle of arrival (AOA), time difference of arrival (TDOA), as well as a combination of AOA/TDOA estimates are developed. The localization accuracy provided by the AOA-based, TDOA-based, and hybrid estimators is evaluated using Cramér–Rao bounds, statistical simulations, and in situ test. Test results demonstrated that the efficiency of AOA-based and TDOA-based estimators strongly depends on variances of the AOA and TDOA estimates. Relative efficiency of the hybrid estimator is higher than any of the AOA-based and TDOA-based algorithms.

Warren, V.E., C. McPherson, G. Giorli, K.T. Goetz, and C.A. Radford

Royal Society Open Science 8(3): 201503 (2021)

DOI: 10.1098/rsos.201503

Baleen whales reliably produce stereotyped vocalizations, enabling their spatio-temporal distributions to be inferred from acoustic detections. Soundscape analysis provides an integrated approach whereby vocal species, such as baleen whales, are sampled holistically with other acoustic contributors to their environment. Acoustic elements that occur concurrently in space, time and/or frequency can indicate overlaps between free-ranging species and potential stressors. Such information can inform risk assessment framework models. Here, we demonstrate the utility of soundscape monitoring in central New Zealand, an area of high cetacean diversity where potential threats are poorly understood. Pygmy blue whale calls were abundant in the South Taranaki Bight (STB) throughout recording periods and were also detected near Kaikōura during autumn. Humpback, Antarctic blue and Antarctic minke whales were detected in winter and spring, during migration. Wind, rain, tidal and wave activity increased ambient sound levels in both deep- and shallow-water environments across a broad range of frequencies, including those used by baleen whales, and sound from shipping, seismic surveys and earthquakes overlapped in time, space and frequency with whale calls. The results highlight the feasibility of soundscape analysis to quantify and understand potential stressors to free-ranging species, which is essential for conservation and management decisions.

von Benda-Beckmann, A.M., S. Isojunno, M. Zandvliet, M.A. Ainslie, P.J. Wensveen, P.L. Tyack, P.H. Kvadsheim, F.P.A. Lam, and P.J.O. Miller

J. Acoust. Soc. Am. 149: 2908-2925 (2021)

DOI: 10.1121/10.0004769

Modern active sonar systems can (almost) continuously transmit and receive sound, which can lead to more masking of important sounds for marine mammals than conventional pulsed sonar systems transmitting at a much lower duty cycle. This study investigated the potential of 1–2 kHz active sonar to mask echolocation-based foraging of sperm whales by modeling their echolocation detection process. Continuous masking for an echolocating sperm whale facing a sonar was predicted for sonar sound pressure levels of 160 dB re 1 μPa2, with intermittent masking at levels of 120 dB re 1 μPa2, but model predictions strongly depended on the animal orientation, harmonic content of the sonar, click source level, and target strength of the prey. The masking model predicted lower masking potential of buzz clicks compared to regular clicks, even though the energy source level is much lower. For buzz clicks, the lower source level is compensated for by the reduced two-way propagation loss to nearby prey during buzzes. These results help to predict what types of behavioral changes could indicate masking in the wild. Several key knowledge gaps related to masking potential of sonar in echolocating odontocetes were identified that require further investigation to assess the significance of masking.

Miksis-Olds, J.L., P.J. Dugan, S.B. Martin, H. Klinck, D.K. Mellinger, D.A. Mann, D.W. Ponirakis, and O. Boebel

Front. Mar. Sci. 8: 703650 (2021)

DOI: 10.3389/fmars.2021.703650

Making Ambient Noise Trends Accessible (MANTA) software is a tool for the community to enable comparisons between soundscapes and identification of ambient ocean sound trends required by ocean stakeholders. MANTA enhances the value of individual datasets by assisting users in creating thorough calibration metadata and internationally recommended products comparable over time and space to ultimately assess ocean sound at any desired scale up to a global level. The software package combines of two applications: MANTA Metadata App, which allows users to specify information about their recordings, and MANTA Data Mining App, which applies that information to acoustic recordings to produce consistently processed, calibrated time series products of sound pressure levels in hybrid millidecade bands. The main outputs of MANTA are daily.csv and NetCDF files containing 60-s spectral energy calculations in hybrid millidecade bands and daily statistics images. MANTA data product size and formats enable easy and compact transfer and archiving among researchers and programs, allowing data to be further averaged and explored to address user-specified questions.

Warren, V.E., A. Širović, C. McPherson, K.T. Goetz, C.A. Radford, and R. Constantine

Frontiers in Marine Science 7: 1162 (2021)

DOI: 10.3389/fmars.2020.575257

Effective management of wild animal populations relies on an understanding of their spatio-temporal distributions. Passive acoustic monitoring (PAM) is a non-invasive method to investigate the distribution of free-ranging species that reliably produce sound. Critically endangered Antarctic blue whales (Balaenoptera musculus intermedia) (ABWs) co-occur with pygmy blue whales (B. m. brevicauda) (PBWs) around New Zealand. Nationally, both are listed as “data deficient” due to difficulties in access and visual sub-species identification. PAM was used to investigate the distributions of blue whales via sub-species specific song detections in central New Zealand. Propagation models, incorporating ambient noise data, enabled the comparison of detections among recording locations in different marine environments. ABW detections peaked during austral winter and spring, indicating that New Zealand, and the South Taranaki Bight (STB) in particular, is a migratory corridor for ABWs. Some ABW calls were also detected during the breeding season (September and October). PBW calls were highly concentrated in the STB, particularly between March and May, suggesting that an aggregation of PBWs may occur here. Therefore, the STB is of great importance for both sub-species of blue whale. PBW detections were absent from the STB during parts of austral spring, but PBWs were detected at east coast locations during this time. Detection area models were valuable when interpreting and comparing detections among recording locations. The results provide sub-species specific information required for management of critically endangered ABWs and highlight the relative importance of central New Zealand for both sub-species of blue whale.

Wilford, D.C., J.L. Miksis-Olds, S.B. Martin, D.R. Howard, K. Lowell, A.P. Lyons, and M.J. Smith

Frontiers in Marine Science 8: 672336 (2021)

DOI: 10.3389/fmars.2021.672336

A methodology for the analysis of soundscapes was developed in an attempt to facilitate efficient and accurate soundscape comparisons across time and space. The methodology consists of a collection of traditional soundscape metrics, statistical measures, and acoustic indices that were selected to quantify several salient properties of marine soundscapes: amplitude, impulsiveness, periodicity, and uniformity. The metrics were calculated over approximately 30 h of semi-continuous passive acoustic data gathered in seven unique acoustic environments. The resultant metric values were compared to a priori descriptions and cross-examined statistically to determine which combination most effectively captured the characteristics of the representative soundscapes. The best measures of amplitude, impulsiveness, periodicity, and uniformity were determined to be SPLrms and SPLpk for amplitude, kurtosis for impulsiveness, an autocorrelation based metric for periodicity, and the Dissimilarity index for uniformity. The metrics were combined to form the proposed “Soundscape Code,” which allows for rapid multidimensional and direct comparisons of salient soundscape properties across time and space. This initial characterization will aid in directing further analyses and guiding subsequent assessments to understand soundscape dynamics.

Booy, K.V., X. Mouy, S.H. Ferguson, and M. Marcoux

Arctic Science 7: 394–412 (2021)

DOI: 10.1139/as-2019-0031

The Cumberland Sound (Nunavut, Canada) beluga whale (Delphinapterus leucas (Pallas, 1776)) population has been designated as threatened and updated biological information about summer distribution is required for a sound recovery plan. Variation in aerial survey counts are speculated to occur due to movement of belugas in and out of the fiord, and there is still uncertainty related to their distribution within key summer habitat. To address these knowledge gaps, non-invasive passive acoustic monitoring (PAM) systems were deployed in August of 2010 and 2011. An automated detector was used to determine presence/absence and quantify calls by recorder site. Results were verified by partial manual analysis of 20% of the files. The detector had a minimum accuracy of 85% for presence/absence and 42% for call quantification. Belugas were detected primarily at the uppermost site of Clearwater Fiord, with detections subsiding with increasing proximity to the fiord entrance. Diel variation in call patterns were quantified at two separate sites in different years, but no correlation was observed between tidal cycles and number of detections. This study indicates that Cumberland Sound beluga may prefer sites at the head of Clearwater Fiord. Further research is required to identify which environmental variables contribute to this observed summer distribution.

Ainslie, M.A., R.K. Andrew, B.M. Howe, and J.A. Mercer

J. Acoust. Soc. Am. 149: 2531–2545 (2021)

DOI: 10.1121/10.0003960

The soundscape of the Northeast Pacific Ocean is studied with emphasis on frequencies in the range 63–125 Hz. A 34-year (1964–1998) increase and seasonal fluctuations (1994–2006) are investigated. This is achieved by developing a simple relationship between the total radiated power of all ocean sound sources and the spatially averaged mean-square sound pressure in terms of the average source factor, source depth, and sea surface temperature (SST). The formula so derived is used to predict fluctuations in the sound level in the range 63–125 Hz with an amplitude of 1.2 dB and a period of 1 year associated with seasonal variations in the SST, which controls the amount of sound energy trapped in the sound fixing and ranging (SOFAR) channel. Also investigated is an observed 5 dB increase in the same frequency range in the Northeast Pacific Ocean during the late 20th century [Andrew, Howe, Mercer, and Dzieciuch (2002). ARLO 3, 65–70]. The increase is explained by the increase in the total number of ocean-going ships and their average gross tonnage.

Urazghildiiev, I.R., B. Martin, and D.E. Hannay

IEEE J. Ocean. Eng. 46: 1057-1067 (2021)

DOI: 10.1109/JOE.2020.3040703

The problem of estimating bearings of impulsive wideband acoustic signals produced by vocalizing animals and received by a compact array of synchronized sensors is addressed. The accuracy provided by the maximum-likelihood (ML), the beamformer (BF), and the time-difference-of-arrival (TDOA) based estimators is evaluated by simulations and in situ tests and compared with the Cramér-Rao bounds. Test results demonstrated that the ML estimator and BF provided similar bearing estimation accuracy for all types of signals. They are more accurate than the TDOA-based estimator for mid- and low-frequency impulsive signals. The accuracy of the TDOA-based estimates comes close to the ML- and BF-based estimates when the signal bandwidth increases. TDOA-based estimators outperformed the BFs and the ML algorithms when estimating the bearings of clicks. The empirical standard deviations provided by the ML/BF and TDOA-based estimators were 0.2° ...3° and 2°...70° for mid- and low-frequency impulsive signals and 5.0° and 0.6° for clicks, respectively.

Mirzaei Hotkani, M., J.-F. Bousquet, S.A. Seyedin, B. Martin, and E. Malekshahi

Acoustics 3: 611-629 (2021)

DOI: 10.3390/acoustics3040039

In this research, a new application using broadband ship noise as a source-of-opportunity to estimate the scattering field from the underwater targets is reported. For this purpose, a field trial was conducted in collaboration with JASCO Applied Sciences at Duncan’s Cove, Canada in September 2020. A hydrophone array was deployed in the outbound shipping lane at a depth of approximately 71 m to collect broadband noise data from different ship types and effectively localize the underwater targets. In this experiment, a target was installed at a distance (93 m) from the hydrophone array at a depth of 25 m. In this study, a matched field processing (MFP) algorithm is utilized for localization. Different propagation models are presented using Green’s function to generate the replica signal; this includes normal modes in a shallow water waveguide, the Lloyd-mirror pattern for deep water, as well as the image model. We use the MFP algorithm with different types of underwater environment models and a proposed estimator to find the best match between the received signal and the replica signal. Finally, by applying the scatter function on the proposed multi-channel cross correlation coefficient time-frequency localization algorithm, the location of target is detected.

Pyć , C.D., J. Vallarta , A.N. Rice, D.G. Zeddies, E.E. Maxner, and S.L. Denes

Conservation Science and Practice 3(5): e352 (2021)

DOI: 10.1111/csp2.352

Vessel‐related noise is a potential stressor for coral reef fauna. The Parque Nacional Arrecifes de Cozumel (PNAC) is a Mexican Marine Protected Area that is exposed to pervasive vessel traffic. PNAC is also the primary range of splendid toadfish (Sanopus splendidus, family Batrachoididae), an IUCN red‐listed soniferous fish for which vessel noise may represent a threat. We conducted a passive acoustic monitoring survey during summer of 2017 at Paraiso Reef in PNAC and obtained the first scientific recordings from splendid toadfish, enabling a vocal characterization of the species. We simultaneously collected data on sound levels of vessels passing near the reef. High noise levels of cruise ship and small motorboat traffic caused elevated anthropogenic sound pressure levels for up to 15 hr per day in the same bandwidth as toadfish vocalizations. A single cruise ship added up to 4 dB above nighttime ambient levels while small motorboat traffic added up to 7 dB. The overlap of toadfish vocalizations and vessel‐related noise highlights the susceptibility of splendid toadfish to acoustic masking and reduction in communication space throughout the day, warranting further study. Because acoustic communication is critical to toadfish reproductive success, noise from cruise ships and small motorboats may threaten splendid toadfish individuals or population viability.

Halliday, W.D., M.K. Pine, S.J. Insley, R.N. Soares, P. Kortsalo, and X. Mouy

Can. J. Zool. 97(1): 72–80 (2019)

DOI: 10.1139/cjz-2018-0077

The Arctic marine environment is changing rapidly through a combination of sea ice loss and increased anthropogenic activity. Given these changes can affect marine animals in a variety of ways, understanding the spatial and temporal distributions of Arctic marine animals is imperative. We use passive acoustic monitoring to examine the presence of marine mammals near Ulukhaktok, Northwest Territories, Canada, from October 2016 to April 2017. We documented bowhead whale (Balaena mysticetus Linnaeus, 1758) and beluga whale (Delphinapterus leucas (Pallas, 1776)) vocalizations later into the autumn than expected, and we recorded bowhead whales in early April. We recorded ringed seal (Pusa hispida (Schreber, 1775)) vocalizations throughout our deployment, with higher vocal activity than in other studies and with peak vocal activity in January. We recorded bearded seals (Erignathus barbatus (Erxleben, 1777)) throughout the deployment, with peak vocal activity in February. We recorded lower bearded seal vocal activity than other studies, and almost no vocal activity near the beginning of the spring breeding season. Both seal species vocalized more when ice concentration was high. These patterns in vocal activity document the presence of each species at this site over autumn and winter and are a useful comparison for future monitoring.

Frouin‑Mouy, H., X. Mouy, C.L. Berchok, S.B. Blackwell, and K.M. Stafford

Polar Biology 42: 657–674 (2019)

DOI: 10.1007/s00300-019-02462-y

Due to the difficulty of studying ice seals in their natural environment, distribution and movement patterns of ribbon seals (Histriophoca fasciata) over large spatio-temporal scales are poorly understood. In this study, we analyzed their distribution patterns in the Bering, Chukchi, and Beaufort seas, using passive acoustic data collected between August 2012 and July 2013 at 53 recording sites. Ribbon seal downsweeps were found using spectrogram correlation autodetection, at 30 of these recording sites. These detections were further manually analyzed to investigate the vocal repertoire and quantify the diel pattern in acoustic presence. We found that the Beaufort Sea shelf and the northern Bering Strait/southern Chukchi Sea are ecologically important for ribbon seals during the open-water season. Our results suggest that the northeastern Chukchi Sea serves as part of a migration corridor to and from the Chukchi Plateau and/or Beaufort Sea. In the Bering Sea, most detections occurred from February to June. Vocal activity was higher at nighttime than during the daytime prior to the peak calling period, while during the peak calling period, diel rhythm became less pronounced. The number of calls, proportional use of downsweeps, and bandwidth of downsweeps (estimated broadband source level 170–178 dB re 1 μPa-m) increased during the breeding period, from March to June, peaking in May. An additional call type, the “shuffle”, was identified in this study. These results improve our understanding of the migration, occurrence, and acoustic behavior of ribbon seals in the Bering, Chukchi, and Beaufort seas.

MacGillivray, A.O.

IEEE J. Ocean. Eng. 44: 582-588 (2019)

DOI: 10.1109/JOE.2018.2853199

JASCO's Airgun Array Source Model (AASM) is a combined deterministic and stochastic model that separately treats the low-frequency and high-frequency components of signals produced by airgun arrays. The low-frequency module is based on solving the equations of motion for interacting spherical bubbles. The high-frequency module is based on a stochastic model of the airgun spectrum, which has been derived from a principal component regression analysis of the experimental data. This stochastic model determines the frequency spectrum of an airgun waveform during the rapid onset of a pressure that occurs when air is released from the gun chamber. AASM combines the output of these two modules to predict the source waveform of an airgun array over a wide frequency range (0-25 kHz). AASM was among the source models included in benchmark comparisons presented at the International Airgun Modeling Workshop (IAMW), held in Dublin, Ireland, in 2016. Results from the workshop showed that different source models agreed reasonably well at low frequencies (<200 Hz), but they diverged substantially at high frequencies (>1 kHz). To help better understand the reasons for a mismatch between source models, this paper presents solutions to the IAMW source test cases, calculated using AASM, as well as a detailed description of AASM's theoretical underpinnings.

Sertlek, H.Ö., M.A. Ainslie, and K.D. Heaney

IEEE J. Ocean. Eng. 44: 1240-1252 (2019)

DOI: 10.1109/JOE.2018.2865640

An analytical formulation for the calculation of the range and depth-dependence of propagation loss in isospeed water is introduced. The range-dependent bathymetry is handled with Weston's ray invariant approach, requiring a gradually varying water depth. The depth dependence of propagation loss is formulated using a transformation from an incoherent mode sum to an integral over angle, in the adiabatic approximation, and the results obtained in this way are tested by comparison with a full adiabatic normal mode sum. The validity of the adiabatic approximation itself is then investigated by means of a comparison with parabolic equation and coupled normal mode results for selected test cases from the Weston Memorial Workshop, held at the University of Cambridge in April 2010. Propagation loss calculations based on different methods are compared. The proposed analytical approach provides practical, fast and accurate results.

Quijano, J.E., D.E. Hannay, and M.E. Austin

IEEE J. Ocean. Eng. 44: 1228-1239 (2019)

DOI: 10.1109/JOE.2018.2858606

In this paper, we present the results of a comprehensive acoustic monitoring and modeling study of the composite underwater noise footprint of an exploration drilling project in shallow waters (46 m) in the northeastern Chukchi Sea. Measured acoustic source levels of multiple vessels and drilling equipment were used as inputs to theoretical propagation models. The models generated time-dependent wide-area noise fields, accounting for oceanographic and weather conditions and the time-dependent drilling activities and positions of multiple vessels. Modeling in increments of 1 h was performed over the full operations period, from July 7, 2015 to October 16, 2015. Model validation was carried out by comparing simulated results with high-resolution acoustic data acquired at multiple stations in the area. The study shows that noise radiating from up to 19 supporting vessels is usually dominant, but noise from certain drilling-related activities occasionally rises above vessel noise within a radius of 8 km from drill sites, limited to a few hours in durations. Modeled scenarios show that by constraining vessel positions to within a few kilometers of the drilling location, the extent of the 120 dB re 1 μPa noise footprint, as defined for single-well and concurrent double-well drilling operations, is contained within a nominal radius of 20 km. Broadband noise from drilling platforms and support vessels reached wind-generated ambient noise levels at ranges between 60 and 85 km from the drill site. Still, some tones and narrowband sounds may remain above the natural ambient noise at the same frequencies to longer ranges.

Martin, S.B. and D.R. Barclay

J. Acoust. Soc. Am. 146: 109-121 (2019)

DOI: 10.1121/1.5114797

Acoustic recordings were made during the installation of four offshore wind turbines at the Block Island Wind Farm, Rhode Island, USA. The turbine foundations have four legs inclined inward in a pyramidal configuration. Four bottom mounted acoustic recorders measured received sound levels at distances of 541–9067 m during 24 pile driving events. Linear mixed models based on damped cylindrical spreading were used to analyze the data. The model's random effects coefficients represented useful information about variability in the acoustic propagation conditions. The received sound levels were dependent on the angle between pile and seabed, strike energy, and pile penetration (PP). Deeper PPs increased sound levels in a frequency dependent manner. The estimated area around the piles where auditory injury and disturbance to marine life could occur were not circular and changed by up to an order of magnitude between the lowest and highest sound level cases. The study extends earlier results showing a linear relationship between the peak sound pressure level and per-strike sound exposure level. Recommendations are made for how to collect and analyze pile driving data. The results will inform regulatory mitigations of the effects of pile driving sound on marine life, and contribute to developing improved pile driving source models.

Thode, A.M., T. Sakai, J. Michalec, S. Rankin, M.S. Soldevilla, B. Martin, and K.H. Kim

J. Acoust. Soc. Am. 146: 95–102 (2019)

DOI: 10.1121/1.5114810

The AN/SSQ-53 Directional Frequency Analysis and Recording (DIFAR) sonobuoy is an expendable device that can derive acoustic particle velocity along two orthogonal horizontal axes, along with acoustic pressure. This information enables computation of azimuths of low-frequency acoustic sources from a single compact sensor. The standard approach for estimating azimuth from these sensors is by conventional beamforming (i.e., adding weighted time series), but the resulting “cardioid” beampattern is imprecise, computationally expensive, and vulnerable to directional noise contamination for weak signals. Demonstrated here is an alternative multiplicative processing scheme that computes the “active intensity” of an acoustic signal to obtain the dominant directionality of a noise field as a function of time and frequency. This information is conveniently displayed as an “azigram,” which is analogous to a spectrogram, but uses color to indicate azimuth instead of intensity. Data from several locations demonstrate this approach, which can be computed without demultiplexing the raw signal. Azigrams have been used to help diagnose sonobuoy issues, improve detectability, and estimate bearings of low signal-to-noise ratio signals. Azigrams may also enhance the detection and potential classification of signals embedded in directional noise fields.

Urazghildiiev, I.R. and D.E. Hannay

IEEE J. Ocean. Eng. 45(3): 1091-1098 (2019)

DOI: 10.1109/JOE.2019.2915913

This paper considers the problem of passive acoustic localization of sources using a network of stationary compact arrays of acoustic sensors providing azimuth and elevation measurements of detected sounds. The maximum-likelihood estimator and Cramér-Rao bounds are derived. The localization accuracy is evaluated using statistical simulations and in situ tests. The plots of azimuth, range, and position estimation accuracy are presented. Test results demonstrated that superefficient position estimates with an error lower than the Cramér-Rao bounds can be achieved for surface vessels and other sound sources with known depths.

Joy, R., D. Tollit, J. Wood, A. MacGillivray, Z. Li, K. Trounce, and O. Robinson

Frontiers in Marine Science 6: 344 (2019)

DOI: 10.3389/fmars.2019.00344

A voluntary commercial vessel slowdown trial was conducted through 16 nm of shipping lanes overlapping critical habitat of at-risk southern resident killer whales (SRKW) in the Salish Sea. From August 7 to October 6, 2017, the trial requested piloted vessels to slow to 11 knots speed-through-water. […] Slowdown results were compared to ‘Baseline’ noise of the same region, matched across lunar months. […] A regional vessel noise model predicted noise for a range of traffic volume and vessel speed scenarios for a 1133 km^2 ‘Slowdown region’ containing the 16 nm of shipping lanes. A temporally and spatially explicit simulation model evaluated the changes in traffic volume and speed on SRKW in their foraging habitat within this Slowdown region. The model tracked the number and magnitude of noise-exposure events that impacted each of 78 (simulated) SRKW across different traffic scenarios. These disturbance metrics were simplified to a cumulative effect termed ‘potential lost foraging time’ that corresponded to the sum of disturbance events described by assumptions of time that whales could not forage due to noise disturbance. […]

MacGillivray, A.O., Z. Li, D.E. Hannay, K.B. Trounce and O.M. Robinson

J. Acoust. Soc. Am. 146: 340-351 (2019)

DOI: 10.1121/1.5116140

During 2017, the Vancouver Fraser Port Authority's Enhancing Cetacean Habitat and Observation program carried out a two-month voluntary vessel slowdown trial to determine whether slowing to 11 knots was an effective method for reducing underwater radiated vessel noise. The trial was carried out in Haro Strait, British Columbia, in critical habitat of endangered southern resident killer whales. During the trial, vessel noise measurements were collected next to shipping lanes on two hydrophones inside the Haro Strait slowdown zone, while a third hydrophone in Strait of Georgia measured vessels noise outside the slowdown zone. Vessel movements were tracked using the automated identification system (AIS), and vessel pilots logged slowdown participation information for each transit. An automated data processing system analyzed acoustical and AIS data from the three hydrophone stations to calculate radiated noise levels and monopole source levels (SLs) of passing vessels. Comparing measurements of vessels participating in the trial with measurements from control periods before and after the trial showed that slowing down was an effective method for reducing mean broadband SLs for five categories of piloted commercial vessels: containerships (11.5 dB), cruise vessels (10.5 dB), vehicle carriers (9.3 dB), tankers (6.1 dB), and bulkers (5.9 dB).

Martin, S.B., C. Morris, K. Bröker, and C. O’Neill

J. Acoust. Soc. Am. 146: 135-149 (2019)

DOI: 10.1121/1.5113578

The auditory frequency weighted daily sound exposure level (SEL) is used in many jurisdictions to assess possible injury to the hearing of marine life. Therefore, using daily SEL to describe soundscapes would provide baseline information about the environment using the same tools used to measure injury. Here, the daily SEL from 12 recordings with durations of 18–97 days are analyzed to: (1) identify natural soundscapes versus environments affected by human activity, (2) demonstrate how SEL accumulates from different types of sources, (3) show the effects of recorder duty cycling on daily SEL, (4) make recommendations on collecting data for daily SEL analysis, and (5) discuss the use of the daily SEL as an indicator of cumulative effects. The autocorrelation of the one-minute sound exposure is used to help identify soundscapes not affected by human activity. Human sound sources reduce the autocorrelation and add low-frequency energy to the soundscapes. To measure the daily SEL for all marine mammal auditory frequency weighting groups, data should be sampled at 64 kHz or higher, for at least 1 min out of every 30 min. The daily autocorrelation of the one-minute SEL provides a confidence interval for the daily SEL computed with duty-cycled data.

Wladichuk, J.L., D.E. Hannay, A.O. MacGillivray, Z. Li, and S. Thornton

Journal of Ocean Technology 14(3): 108-126 (2019)

JOT Article page

Marine mammals rely heavily on sound for foraging, communicating, and navigating. As noise in the ocean increases, their ability to perform these important life functions can be affected. In the past decade, numerous studies have expanded our awareness of the effects of anthropogenic noise on marine life. Improving our knowledge of how sound impacts marine mammals is particularly important in coastal waters where the spatial distributions of vessels and marine mammals overlap, as exemplified by the critical habitat for the endangered Southern Resident killer whale (Orcinus orca). The impacts of small vessel traffic (including the commercial and recreational whale watching that is directed on this population) has been difficult to assess as there is a data gap for small vessel noise emissions. In this study, two autonomous marine acoustic recorders were deployed in transboundary Haro Strait (British Columbia, Canada, and Washington State, USA) from July to October 2017 to measure sound levels produced by whale watching vessels and other small boats. […]

Burnham, R.E., D.A. Duffus, and X. Mouy

Continental Shelf Research 177: 15–23 (2019)

DOI: 10.1016/j.csr.2019.03.004

Large whale populations in the northeast Pacific were severely reduced by whaling, with many showing limited recovery. Their use of offshore waters and limited knowledge of life histories has hindered studies focused on estimating population numbers and mapping habitat use. Acoustic recordings, using vocalizations as a marker of whale presence, may be the first step in re-establishing baseline knowledge of species presence over time and space. Recordings from both stationary and mobile platforms, covering waters from coastal to shelf-break and offshore waters, show spatial segregation in the dominant species recorded. Inshore recordings are dominated by more coastally-focused species, whereas fin (Balaenoptera physalus) blue (Balaenoptera musculus) and sperm whales (Physeter macrocephalus) are primarily heard in the shelf-break zones. Calls tentatively described for sei whales (Balaenoptera borealis) are also noted. Calls matching those previously described to these species as breeding and foraging calls were found. Acoustic monitoring surveys like this study are needed to better map presence and habitat use of these rare and endangered species, ultimately leading to the identification and protection of areas important to population recovery.

Kowarski, K., H. Moors-Murphy, E. Maxner, and S. Cerchio

J. Acoust. Soc. Am. 145: 2305–2316 (2019)

DOI: 10.1121/1.5095404

Humpback whale songs have been described worldwide and studies exploring non-song vocal behavior continue to expand; however, studies on the transition periods when whales shift to and from the seasonal behavioral state of singing are lacking and may be potentially informative regarding the proximal factors controlling the onset and offset of humpback whale male singing. Acoustic recorders collected data off eastern Canada continuously from the Bay of Fundy in the fall of 2015 and near-continuously off northeast Nova Scotia in the spring of 2016. Humpback whale acoustic occurrence and behavior were identified by systematically reviewing a subset of acoustic recordings for presence before analyzing the highest quality recordings for behavior. The onset of singing in the fall was gradual over a period of about three weeks with an intermediate form, termed “song fragment,” occurring prior to full songs. In comparison, singing in the spring seemed to end abruptly with few song fragments. Song fragments could be produced by juveniles learning to sing for the first time or mature males preparing for breeding activities prior to migrating to southern breeding grounds. The authors propose an alternative hypothesis that the timing and manner of transitions could be driven by physiological processes similar to those documented in songbirds.

Austin, M.E., D.E. Hannay, and K.C. Bröker

Journal of the Acoustical Society of America 144: 115–123 (2018)

DOI: 10.1121/1.5044417

This paper characterizes underwater sound levels produced by three drilling units during offshore exploration drilling at three sites in the Beaufort and Chukchi seas. Received levels and spectra are reported as functions of distance during drilling and excavation of mudline cellars (MLCs). Sound levels emitted during MLC excavation exceeded those during drilling at all three sites, although this operation was much shorter in duration. Drilling sounds exhibited tones below 2 kHz, with harmonics present to 10 kHz, while MLC excavation sounds were broadband in character. Drilling sounds varied substantially between the three operations, whereas MLC excavation sounds were more consistent in amplitude and spectral distribution. Estimates of broadband and 1/3-octave band source levels were computed from measurements at 1 km range. The broadband drilling source levels were 168.6 dB re 1 μPa m for the Kulluk drilling unit, 174.9 dB re 1 μPa m for the drillship Noble Discoverer, and 170.1 dB re 1 μPa m for the semi-submersible Polar Pioneer. The received levels measured at 1 km during MLC excavation yielded source level estimates that were more consistent among sources: 191.8, 193.0, and 193.3 dB re 1 μPa for the Discoverer, Kulluk, and Polar Pioneer, respectively.

Pine, M.K., D.E. Hannay, S.J. Insley, W.D. Halliday, and F. Juanes

Marine Pollution Bulletin 135: 290-302 (2018)

DOI: 10.1016/j.marpolbul.2018.07.031

Vessel slowdown may be an alternative mitigation option in regions where re-routing shipping corridors to avoid important marine mammal habitat is not possible. We investigated the potential relief in masking in marine mammals and fish from a 10 knot speed reduction of container and cruise ships. The mitigation effect from slower vessels was not equal between ambient sound conditions, species or vessel-type. Under quiet ambient conditions, a speed reduction from 25 to 15 knots resulted in smaller listening space reductions by 16–23%, 10–18%, 1–2%, 5–8% and 8% respectively for belugas, bowheads, bearded seals, ringed seals, and fish, depending on vessel-type. However, under noisy conditions, those savings were between 9 and 19% more, depending on the species. This was due to the differences in species' hearing sensitivities and the low ambient sound levels measured in the study region. Vessel slowdown could be an effective mitigation strategy for reducing masking.

Kastelein, R.A., L. Helder-Hoek, S. Van de Voorde, S. de Winter, S. Janssen, and M.A. Ainslie

Aquatic Mammals 44: 389-404 (2018)

DOI: 10.1578/AM.44.4.2018.389

Naval sonar signals may affect the behavior of harbor porpoises (Phocoena phocoena). The 53C sonar system produces 1,600 ms sonar signals in the 3.5 to 4.1 kHz band, each consisting of a sweep immediately followed by two tones which are separated by a 100 ms silence. Effects of sound pressure level (SPL) and duty cycle on the behavioral responses of two harbor porpoises to these sounds were investigated. Respiration rate, distance to the transducer, swimming speed, and the number of jumps during sound exposure and baseline periods were compared. Harbor porpoises were exposed to 30-min playbacks of 53C sonar sounds at five average received SPLs (Lrecs) with a duty cycle of 2.7%, and at six Lrecs with a duty cycle of 96%, under low ambient noise conditions. They did not respond to the sounds when the duty cycle was 2.7%, even at the maximum Lrec (143 dB re 1 μPa). When the duty cycle was 96%, only Porpoise 06 increased his respiration rate when the Lrec was ≥119 dB re 1 μPa, and he moved away from the transducer only at an Lrec of 143 dB re 1 μPa. At the same Lrec and duty cycle, the effect of 53C sonar sounds on harbor porpoise behavior was weaker than that of 1 to 2 kHz, 6 to 7 kHz, and 25 kHz sonar signals observed in previous studies.

Cominelli, S., R. Devillers, H. Yurk, A. MacGillivray, L. McWhinnie, and R. Canessa

Marine Pollution Bulletin 136: 177-200 (2018)

DOI: 10.1016/j.marpolbul.2018.08.050

This study assesses vessel-noise exposure levels for Southern Resident Killer Whales (SRKW) in the Salish Sea. Kernel Density Estimation (KDE) was used to delineate SRKW summer core areas. Those areas were combined with the output of a regional cumulative noise model describing sound level variations generated by commercial vessels (1/3-octave-bands from 10 Hz to 63.1 kHz). Cumulative distribution functions were used to evaluate SRKW's noise exposure from 15 vessel categories over three zones located within the KDE. Median cumulative noise values were used to group categories based on the associated exposure levels. Ferries, Tugboats, Vehicle Carriers, Recreational Vessels, Containers, and Bulkers showed high levels of exposure (Leq−50th > 90 dB re 1 μPa) within SRKW core areas. Management actions aiming at reducing SRKW noise exposure during the summer should target the abovementioned categories and take into consideration the spatial distribution of their levels of exposure, their mechanical and their operational characteristics.

Urazghildiiev, I.R. and D.E. Hannay

Journal of the Acoustical Society of America 143: 2825-2833 (2018)

DOI: 10.1121/1.5037361

The problem of estimating the number of sound-producing sources detected using a compact array of hydrophones is addressed. Closed form expressions representing the techniques of automatic detection and estimation of the number of callers are given. Their performance is evaluated on a year-long dataset (1 October 2015–6 October 2016) containing humpback whale and killer whale calls collected in the Strait of Georgia, near Vancouver, British Columbia. Manual verification of the automatic detections produced by the approach required ∼40 h.

Farmer, N.A., K. Baker, D.G. Zeddies, S.L. Denes, D.P. Noren, L.P. Garrison, A. Machernis, E.M. Fougères, and M. Zykov

Biological Conservation 227: 189-204 (2018)

DOI: 10.1016/j.biocon.2018.09.006

Sperm whale (Physeter macrocephalus) populations are still recovering from massive population declines associated with commercial whaling operations. The species continues to face a suite of contemporary threats, including pollution, ship strikes, fisheries interactions, habitat loss and degradation, oil spills, and anthropogenic noise. The sperm whale stock in the northern Gulf of Mexico was exposed to oil from the Deepwater Horizon (DWH) oil spill and is exposed to high levels of anthropogenic noises generated by geological and geophysical (G&G) surveys for hydrocarbon deposits. Population impacts from oil and gas activities were predicted from models that incorporated two stressors: (i) oil exposure from DWH and (ii) noise from G&G surveys. Oil exposure was projected to reduce survival and reproductive success, causing a mean stock decline of 26% by 2025. Additionally, exposure to underwater noise can adversely impact whale hearing, communication, foraging efficiency, and disturb essential behaviors. Exposures to G&G survey noise were determined by simulating individual movements through three-dimensional sound fields generated by different survey methods. Behavioral disturbance was evaluated as reduced foraging opportunities under four dose-response functions. Bioenergetic models tracked the depletion of reserves in blubber, muscle, and viscera. All simulations suggested significant reductions in relative fitness of reproductive females were a likely consequence of persistent disturbances to foraging behaviors. Under a 160 dB SPL unweighted dose-response function, up to 4.4 ± 0.3% of the stock may reach terminal starvation due to behavioral disturbance associated with future G&G surveys, leading to abortions, calf abandonment, and up to 25% greater stock declines beyond those predicted from DWH oil exposure. Uncertainty in our results emphasizes a need for further controlled exposure experiments to generate behavioral disturbance dose-response curves and detailed evaluation of individual resilience following disturbance events. Given our focus on a limited suite of threats and need for field verification of these modeled impacts, precautionary management application of our results is recommended for this endangered species.

Kowarski, K., J. Delarue, B. Martin, J. O’Brien, R. Meade, O.Ó. Cadhla, and S. Berrow

PLoS ONE 13: e0199431 (2018)

DOI: 10.1371/journal.pone.0199431

Little is known of the spatio-temporal occurrence of beaked whales off western Ireland, limiting the ability of Regulators to implement appropriate management and conservation measures. To address this knowledge gap, static acoustic monitoring was carried out using eight fixed bottom-mounted autonomous acoustic recorders: four from May to December 2015 on Ireland’s northern slope and four from March to November 2016 on the western and southern slopes. Recorders ran for 205 to 230 days, resulting in 4.09 TB of data sampled at 250 kHz which could capture beaked whale acoustic signals. Zero-crossing-based automated detectors identified beaked whale clicks. A sample of detections was manually validated to evaluate and optimize detector performance. Analysis confirmed the occurrence of Sowerby’s and Cuvier’s beaked whales and Northern bottlenose whales. Northern bottlenose whale clicks occurred in late summer and autumn, but were too few to allow further analysis. Cuvier’s and Sowerby’s clicks occurred at all stations throughout the monitoring period. There was a significant effect of month and station (latitude) on the mean daily number of click detections for both species. Cuvier’s clicks were more abundant at lower latitudes while Sowerby’s were greater at higher latitudes, particularly in the spring, suggesting a spatial segregation between species, possibly driven by prey preference. Cuvier’s occurrence increased in late autumn 2015 off northwest Porcupine Bank, a region of higher relative occurrence for each species. Seismic airgun shots, with daily sound exposure levels as high as 175 dB re 1 μPa^2·s, did not appear to impact the mean daily number of Cuvier’s or Sowerby’s beaked whale click detections. This work provides insight into the significance of Irish waters for beaked whales and highlights the importance of using acoustics for beaked whale monitoring.

Kowarski, K., C. Evers, H. Moors-Murphy, B. Martin, and S.L. Denes

Marine Mammal Science 34: 169-189 (2018)

DOI: 10.1111/mms.12447

Humpback whale use of areas off eastern Canada is poorly understood, a knowledge gap that could impact future conservation efforts. We describe the acoustic occurrence of humpback whales in and around the Gully Marine Protected Area (MPA), an eastern Scotian Shelf submarine canyon. Near-continuous acoustic recordings sampling at 16 kHz were collected from the MPA and nearby slope areas from October 2012 to September 2014 using near-bottom recorders. In an offshore region where humpbacks were thought to be rare, we observed calls from October to June with a peak in song and nonsong calls in December and January. This suggests that some individuals occur in Canadian waters in winter and the Gully region may be a North Atlantic humpback whale migratory corridor. Calls were predominantly songs indicating potential mating activities. Song and nonsong calls occurred more at sunset and during hours of darkness than during daylight. This study improves our understanding of the seasonal occurrence of humpback whales on the Scotian Slope and, more specifically, their use of an offshore protected area.

MacGillivray, A.

Journal of the Acoustical Society of America 143: 450-459 (2018)

DOI: 10.1121/1.5021554

Underwater noise from impact pile driving of 512 -m-long conductor casings was measured at a deep-water offshore oil platform in the Santa Barbara Channel. Beamforming measurements, obtained with a vertical array, confirmed that the primary wave front generated by hammering the conductor casing was a Mach cone propagating at an angle of 17.6° below the horizontal. Analysis of the processed array data also revealed the presence of high-frequency secondary waves at angles steeper than 45° below the horizontal. These secondary waves, which appeared to be generated near the sea-surface, dominated the acoustic spectrum of the pulses at frequencies above 1 kHz. Shallow hydrophone measurements outside the Mach cone showed clear evidence of a surface shadow zone, which was caused by the strong downward directivity of the source. Although reflected waves, diffraction, and secondary waves still produced sound inside the surface shadow zone, sound levels were 10–15 dB lower in this region. Long-term hydrophone measurements showed that there was little difference (±1 dB) in mean sound levels from impact hammering of different conductors installed at the same platform over three months.

Giorli, G., K.T. Goetz, T. Kimberly, J. Delarue, E. Maxner, K.A. Kowarski, S. Bruce Martin, and C. McPherson

Journal of the Acoustical Society of America 143:EL285-EL291 (2018)

DOI: 10.1121/1.5032127

The echolocation signals of most beaked whale species are still unknown. In fact, out of the 22 species comprising the family Ziphiidae, only the echolocation pulses for 7 species have been clearly described. This study describes two distinct beaked whale echolocation signals recorded in the Cook Strait region using passive acoustic technology. These signals differ from previously described Ziphiid species clicks. A description of the time-frequency characteristics of the two signals is provided. Understanding the characteristics of these signals is necessary to correctly identify species from their echolocation signals and enables future monitoring of beaked whales using passive acoustics techniques.

Urazghildiiev, I.R. and D.E. Hannay

IEEE J. Ocean. Eng. 43: 1134–1142 (2018)

DOI: 10.1109/JOE.2017.2772984

Compact arrays of acoustic sensors can provide bearing measurements of detected sounds. An important application for compact arrays is estimating the motion parameters of sources. This work considers the problem of bearings-only estimating of the positions and heading angles of vessels in the presence of bearing and speed measurement errors. Statistical simulations are used to evaluate the dependence of bearing estimation accuracy on the duration of the observation interval and the variance of speed errors. Plots of range and heading estimation errors obtained for 171 vessel passes with known positions are presented. Test results demonstrate that the accuracy of the estimating range depends strongly on speed error variance.

Warner, G.A., S.E. Dosso, and D.E. Hannay

Journal of the Acoustical Society of America 141: 1921-1935 (2017)

DOI: 10.1121/1.4978438

This paper estimates bowhead whale locations and uncertainties using nonlinear Bayesian inversion of the time-difference-of-arrival (TDOA) of low-frequency whale calls recorded on onmi-directional asynchronous recorders in the shallow waters of the northeastern Chukchi Sea, Alaska. A Y-shaped cluster of seven autonomous ocean-bottom hydrophones, separated by 0.5–9.2 km, was deployed for several months over which time their clocks drifted out of synchronization. Hundreds of recorded whale calls are manually associated between recorders. The TDOA between hydrophone pairs are calculated from filtered waveform cross correlations and depend on the whale locations, hydrophone locations, relative recorder clock offsets, and effective waveguide sound speed. A nonlinear Bayesian inversion estimates all of these parameters and their uncertainties as well as data error statistics. The problem is highly nonlinear and a linearized inversion did not produce physically realistic results. Whale location uncertainties from nonlinear inversion can be low enough to allow accurate tracking of migrating whales that vocalize repeatedly over several minutes. Estimates of clock drift rates are obtained from inversions of TDOA data over two weeks and agree with corresponding estimates obtained from long-time averaged ambient noise cross correlations. The inversion is suitable for application to large data sets of manually or automatically detected whale calls.

Martin, S.B., M.-N.R. Matthews, J.T. MacDonnell, and K. Bröker

Journal of the Acoustical Society of America 142: 3331-3346 (2017)

DOI: 10.1121/1.5014049

In 2012 a seismic survey campaign involving four vessels was conducted in Baffin Bay, West Greenland. Long-distance (150 km) pre-survey acoustic modeling was performed in accordance with regulatory requirements. Four acoustic recorders, three with hydrophones at 100, 200, and 400 m depths, measured ambient and anthropogenic sound during the survey. Additional recordings without the surveys were made from September 2013 to September 2014. The results show that (1) the soundscape of Baffin Bay is typical for open ocean environments and Melville Bay's soundscape is dominated by glacial ice noise; (2) there are distinct multipath arrivals of seismic pulses 40 km from the array; (3) seismic sound levels vary little as a function of depth; (4) high fidelity pre-survey acoustic propagation modeling produced reliable results; (5) the daily SEL did not exceed regulatory thresholds and were different using Southall, Bowles, Ellison, Finneran, Gentry, Greene, Kastak, Ketten, Miller, Nachtigall, Richardson, Thomas, and Tyack [(2007) Aquat. Mamm. 33, 411–521] or NOAA weightings [National Marine Fisheries Service (2016). NOAA Technical Memorandum NMFS-OPR-55, p. 178]; (6) fluctuations of SPL with range were better described by additive models than linear regression; and (7) the survey increased the 1-min SPL by 28 dB, with most of the energy below 100 Hz; energy in the 16 000 Hz octave band was 20 dB above the ambient background 6 km from the source.

Horwich, L., J. Prowse, A. MacGillivray, B. Martin, S. Molloy, W. Renaud, and D. Hannay

Canadian Acoustics 45(2): 13-15 (2017)

jcaa.caa-aca.ca/index.php/jcaa/article/view/3041

Man-made ocean noise can cause physical injury and behavioral disturbance to marine life. It hampers marine mammals’ use of sound for foraging, communicating, navigating, socializing, and mating. Advancements in acoustic recorders, ocean observatories, vessel tracking, and noise modelling allow us to study and manage the effects of vessel noise on marine life. This paper discusses a study for the Canadian Space Agency to investigate the feasibility of a user-controlled web interface that provides near-real-time prediction of vessel noise in marine life habitats. ‘ShipNoiseView’ integrates live vessel position data from the Satellite-Automatic Identification System (S-AIS) with real-time remote sensing of oceanographic data and verified vessel noise propagation models to assess cumulative vessel sound levels and to manage the effect of noise on marine life through real-time monitoring and mitigation.

Morris, C.J., D. Cote, B. Martin, and D. Kehler

Fisheries Research 197: 67–77 (2017)

DOI: 10.1016/j.fishres.2017.09.012

Sound is used by a variety of marine taxa for feeding, reproduction, navigation and predator avoidance and therefore alterations to the soundscape from industrial noise have the potential to negatively affect an animal’s fitness. Furthermore, responses to industrial noise would also have the potential to negatively influence commercial fishing interests. Unfortunately marine invertebrates are generally underrepresented in the seismic effects literature. Snow crab harvesters in Atlantic Canada contend that seismic noise from widespread hydrocarbon exploration has strong negative effects on catch rates. We repeated a Before-After-Control-Impact study over two years to assess the effects of industry scale seismic exposure on catch rates of snow crab along the continental slope of the Grand Banks of Newfoundland. Our results did not support the contention that seismic activity negatively affects catch rates in shorter term (i.e. within days) or longer time frames (weeks). However, significant differences in catches were observed across study areas and years. While the inherent variability of the CPUE data limited the statistical power of this study, our results do suggest that if seismic effects on snow crab harvests do exist, they are smaller than changes related to natural spatial and temporal variation.

Davis, G.E. M.F. Baumgartner, J.M. Bonnell, J. Bell, C. Berchok, J. Bort Thornton, S. Brault, G. Buchanan, … J. Delarue, … B. Martin, et al.

Scientific Reports 7: 13460 (2017)

DOI: 10.1038/s41598-017-13359-3

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.

Urazghildiiev, I.R. and D. Hannay

Journal of the Acoustical Society of America 141: 2548-2555 (2017)

DOI: 10.1121/1.4979792

The problem of estimating the azimuth and elevation angle of a sound source using a compact array of hydrophones is addressed. The closed-form representations for several time-difference of arrival (TDOA) based estimators are given, and their accuracies are evaluated using both statistical simulations and in situ tests. Simulations demonstrated that the accuracy provided by the estimators is close to the Cramér–Rao bounds. In real conditions, the main cause of azimuth and elevation errors can be refraction, surface and bottom reflections and other unpredictable sound propagation effects resulting in large and slowly changing errors.

Frouin-Mouy, H., K. Kowarski, B. Martin, and K. Bröker

Arctic 70: 59-76 (2017)

DOI: 10.14430/arctic4632

The expansion of hydrocarbon exploration in northwest Greenland has made it increasingly important to understand the occurrence of marine mammals in the region. We describe the seasonal occurrence of marine mammals and the spatial distribution of their calls in Baffin Bay and Melville Bay. Four Autonomous Multichannel Acoustic Recorders (AMARs) were deployed during summer 2012 (late July to early October), five recorders during September 2013, and two recorders from late September 2013 to early September 2014. The call presence of several species was analyzed using automatic call detection and manual verification analysis methods. A novel approach to discern narwhal (Monodon monoceros) clicks from beluga (Delphinapterus leucas) clicks was implemented during the verification process. Narwhal calls were detected in spring and fall, showing a south-to-north migration pattern in spring and a north-to-south migration pattern in fall. Few beluga whales were detected during fall 2013 and spring 2014. Bearded seal (Erignathus barbatus) calls were detected mainly during spring (mating period). A small number of bowhead whale calls (Balaena mysticetus) were detected during fall 2013 and spring and summer 2014. For the first time at this latitude in Baffin Bay, long-finned pilot whales (Globicephala melas) and sperm whales (Physeter macrocephalus) were detected during summer and fall. Our results suggest that the presence of marine mammals in Baffin Bay and Melville Bay is governed mainly by the annual cycle of sea ice formation and decay.

Erbe, C. and C. McPherson

Journal of the Acoustical Society of America 142: EL281-EL285 (2017)

DOI: 10.1121/1.5003328

Geotechnical site investigations prior to marine construction typically involve shallow, small-core drilling and standard penetration testing (SPT), during which a small tube is hammered into the ground at the bottom of the borehole. Drilling (120 kW, 83 mm diameter drillbit, 1500 rpm, 16–17 m drill depth in sand and mudstone) and SPT (50 mm diameter test tube, 15 mm wall thickness, 100 kg hammer, 1 m drop height) by a jack-up rig in 7–13 m of water were recorded with a drifting hydrophone at 10–50 m range. Source levels were 142–145 dB re 1 μPa rms @ 1 m (30–2000 Hz) for drilling and 151–160 dB re 1 μPa2s @ 1 m (20–24 000 Hz) for SPT.

Urazghildiiev, I.R. and S.M. Van Parijs

Journal of the Acoustical Society of America 139: 2532-2540 (2016)

DOI: 10.1121/1.4948569

Northwest Atlantic cod (Gadus morhua) have been heavily overfished in recent years and have not yet recovered. Passive acoustic technology offers a new approach to identify the spatial location of spawning fish, as well as their seasonal and long term persistence in an area. To date, the lack of a species-specific detector has made searching for Atlantic cod grunts in large amounts of passive acoustic data cumbersome. To address this problem, an automatic grunt detection and recognition algorithm that processes yearlong passive acoustic data recordings was designed. The proposed technique is a two-stage hypothesis testing algorithm that includes detecting and recognizing all grunt-like sounds. Test results demonstrated that the algorithm provided a detection probability of 0.93 for grunts with a signal-to-noise ratio (SNR) higher than 10 dB, and a detection probability of 0.8 for grunts with the SNR ranging from 3 to 10 dB. This detector is being used to identify cod in current and historical data from U.S. waters. Its use has significantly reduced the time required to find and validate the presence of cod grunts.

Gailey, G., O. Sychenko, T. McDonald, R. Racca, A. Rutenko, and K. Bröker

Endangered Species Research 30: 53-71 (2016)

DOI: 10.3354/esr00713

A seismic survey was conducted off the northeastern coast of Sakhalin Island, Russia in 2010. The survey area was adjacent to the only known near-shore feeding ground of the Critically Endangered population of western gray whales Eschrichtius robustus in the western Pacific south of the Aleutian Islands. This study examined the effectiveness of efforts to minimize the behavioural responses of the whales to vessel proximity and sound during the survey. Two shore-based behavioural observation teams monitored whale movements and respirations pre-, during and post-seismic survey. Theodolite tracking and focal-animal follow methods were used to collect behavioural data. Mixed linear models were used to examine deviations from ‘normal’ patterns in 10 movement and 7 respiration response variables in relation to vessel proximity, vessel/whale relative orientations and 8 received sound metrics to examine if seismic survey sound and/or vessel activity influenced the whales’ behaviour. Behavioural state and water depth were the best ‘natural’ predictors of whale movements and respiration. After considering natural variation, none of the response variables were significantly associated with seismic survey or vessel sounds. A whale’s distance from shore and its orientation relative to the closest vessel were found to be significantly influenced by vessel proximity, which suggested some non-sound related disturbance. The lack of evidence that the whales responded to seismic survey sound and vessel traffic by changing either their movement or respiration patterns could indicate that the current mitigation strategy is effective. However, power analyses suggest that our sample sizes were too small to detect subtle to moderate changes in gray whale behaviour.

Warner, G.A., S.E. Dosso, D.E. Hannay, and J. Dettmer

Journal of the Acoustical Society of America 140: 20-34 (2016)

DOI: 10.1121/1.4954755

This paper estimates bowhead whale locations and uncertainties using non-linear Bayesian inversion of their modally-dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of 7 asynchronous ocean-bottom hydrophones that were separated by 0.5–9.2 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, seabed geoacoustic parameters, relative recorder clock drifts, and residual error standard deviations, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization as long as the inversion treats the environment as unknown. Joint inversion of multiple recorded calls is shown to substantially reduce uncertainties in location, source IF, and relative clock drift. Whale location uncertainties are estimated to be 30–160 m and relative clock drift uncertainties are 3–26 ms.

Lippert, S., M. Nijhof, T. Lippert, D. Wilkes, A. Gavrilov, K. Heitmann, M. Ruhnau, O. von Estorff, A. Schäfke, … A. MacGillivray, … M. Wood, et al.

IEEE J. Ocean. Eng. 41: 1061-1071 (2016)

DOI: 10.1109/JOE.2016.2524738

The prediction of underwater noise emissions from impact pile driving during near-shore and offshore construction activities and its potential effect on the marine environment has been a major field of research for several years. A number of different modeling approaches have been suggested recently to predict the radiated sound pressure at different distances and depths from a driven pile. As there are no closed-form analytical solutions for this complex class of problems and for a lack of publicly available measurement data, the need for a benchmark case arises to compare the different approaches. Such a benchmark case was set up by the Institute of Modelling and Computation, Hamburg University of Technology (Hamburg, Germany) and the Organisation for Applied Scientific Research (TNO, The Hague, The Netherlands). Research groups from all over the world, who are involved in modeling sound emissions from offshore pile driving, were invited to contribute to the first so-called COMPILE (a portmanteau combining computation, comparison, and pile) workshop in Hamburg in June 2014. In this paper, the benchmark case is presented, alongside an overview of the seven models and the associated results contributed by the research groups from six different countries. The modeling results from the workshop are discussed, exhibiting a remarkable consistency in the provided levels out to several tens of kilometers. Additionally, possible future benchmark case extensions are proposed.

Muir, J.E., L. Ainsworth, R. Racca, Y. Bychkov, G. Gailey, V. Vladimirov, S. Starodymov, and K. Bröker

Endangered Species Research 29: 211-227 (2016)

DOI: 10.3354/esr00709

Some whale populations that were severely reduced by commercial whaling have shown strong recovery since becoming protected, while others remain depleted and of high conservation concern. Small populations are particularly susceptible to anthropogenic threats, including acoustic disturbance from industrial activities such as seismic surveys. Here, we investigated if sound exposure from a 16 d seismic survey displaced gray whales Eschrichtius robustus from their coastal feeding area off northeastern Sakhalin Island, Russia. We conducted multiple shore-based surveys per day, weather permitting, and created daily 1 km2 density surfaces that provided snapshots of gray whale distribution throughout the seismic activity. A Bayesian spatio-temporal analysis was used to examine possible effects of characteristics of sound exposure from seismic airguns on gray whale occupancy and abundance. Models suggested highest occupancy in areas with moderate sound exposure. Slightly decreased densities were associated with sound exposure when the pattern for the previous 3 d was high sound on Day 2 and low sound on Days 1 and 3. Our findings should be interpreted with caution, given the low number of positive densities. This was due to success of the primary mitigation measure, which was to conduct the seismic survey as early in the feeding season as possible when few gray whales would be present. It is also possible that observed differences in occupancy and density reflect changes in prey availability rather than noise. Prey distribution and abundance data were unavailable for our study, and this important covariate could not be included in models.

Ellison, W.T., R. Racca, C.W. Clark, B. Streever, A.S. Frankel, E. Fleishman, R. Angliss, J. Berger, D. Ketten, et al.

Endangered Species Research 30: 95-108 (2016)

DOI: 10.3354/esr00727

Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by researchers and regulators on the basis of exposure to a single, relatively loud sound source. However, marine mammals typically receive sounds from multiple, dynamic sources. We developed a method to aggregate modeled sounds from multiple sources and estimate the sound levels received by individuals. To illustrate the method, we modeled the sound fields of 9 sources associated with oil development and estimated the sound received over 47 d by a population of 10000 simulated bowhead whales Balaena mysticetus on their annual migration through the Alaskan Beaufort Sea. Empirical data were sufficient to parameterize simulations of the distribution of individual whales over time and their range of movement patterns. We ran 2 simulations to estimate the sound exposure history and distances traveled by bowhead whales: one in which they could change their movement paths (avert) in response to set levels of sound and one in which they could not avert. When animals could not avert, about 2% of the simulated population was exposed to root mean square (rms) sound pressure levels (SPL) ≥180 dB re 1 µPa, a level that regulators in the U.S. often associate with injury. When animals could avert from sound levels that regulators often associate with behavioral disturbance (rms SPL >160 dB re 1 µPa), <1% of the simulated population was exposed to levels associated with injury. Nevertheless, many simulated bowhead whales received sound levels considerably above ambient throughout their migration. Our method enables estimates of the aggregated level of sound to which populations are exposed over extensive areas and time periods.

Nikolich, K., H. Frouin-Mouy, and A. Acevedo-Gutiérrez

Journal of the Acoustical Society of America 140: 1300-1308 (2016)

DOI: 10.1121/1.4961008

During breeding season, male harbor seals (Phoca vitulina) produce underwater calls used in sexual competition and advertisement. Call characteristics vary among populations, and within-population differences are thought to represent individual variation. However, vocalizations have not been described for several populations of this widely-distributed and genetically diverse species. This study describes the vocal repertoire of harbor seals from British Columbia, Canada. Underwater recordings were made near Hornby Island during the summer of 2014 using a single hydrophone. A wide variability was detected in breeding vocalizations within this single breeding site. Four candidate call types were identified, containing six subtypes. Linear discriminant analysis showed 88% agreement with subjective classification of call types, and 74% agreement for call subtypes. Classification tree analysis gave a 92% agreement with candidate call types, with all splits made on the basis of call duration. Differences in duration may have reflected individual differences among seals. This study suggests that the vocal repertoire of harbor seals in this area comprises a vocal continuum rather than discrete call types. Further work with the ability to localize calls may help to determine whether this complexity represents variability due to propagation conditions, animal orientation, or differences among individual seals.

Martin, S.B. and A.N. Popper

Journal of the Acoustical Society of America 139: 1886-1897 (2016)

DOI: 10.1121/1.4944876

There is a growing body of research on natural and man-made sounds that create aquatic soundscapes. Less is known about the soundscapes of shallow waters, such as in harbors, rivers, and lakes. Knowledge of soundscapes is needed as a baseline against which to determine the changes in noise levels resulting from human activities. To provide baseline data for the Hudson River at the site of the Tappan Zee Bridge, 12 acoustic data loggers were deployed for a 24-h period at ranges of 0–3000 m from the bridge, and four of the data loggers were re-deployed for three months of continuous recording. Results demonstrate that this region of the river is relatively quiet compared to open ocean conditions and other large river systems. Moreover, the soundscape had temporal and spatial diversity. The temporal patterns of underwater noise from the bridge change with the cadence of human activity. Bridge noise (e.g., road traffic) was only detected within 300 m; farther from the bridge, boating activity increased sound levels during the day, and especially on the weekend. Results also suggest that recording near the river bottom produced lower pseudo-noise levels than previous studies that recorded in the river water column.

Burham, R., R. Palm, D. Duffus, X. Mouy, and A. Riera

Global Ecology and Conservation 8: 24-30 (2016)

DOI: 10.1016/j.gecco.2016.08.001

Observations of cetaceans during the winter are difficult, if not impossible in some locations, yet their presence, habitat use, and behaviour during this period are important for conservation and management. Typically, observations come from vessel surveys, with citizen science networks increasingly adding significant sighting data. In compliment to this, acoustic data collection systems can be deployed to collect information remotely over long periods, and in almost any conditions. Here we describe how the combination of these data collection techniques works to fill knowledge gaps, with data from a well-established citizen science network, and a single passive acoustic monitoring (PAM) recorder integrated to identify killer whale presence during winter months in Clayoquot Sound, on the west coast of Vancouver Island.

Together these data show the overwinter use of Clayoquot Sound by killer whales is greater than previously thought. During the study period, February 21 to April 25, 2015, the citizen science network noted 14 visual encounters ranging from Amphitrite Point to Hot Spring Cove, Vancouver Island. The PAM recorded 17 acoustic encounters within the 10 km detection radius of the recorder, deployed off Siwash Point, Flores Island. This included 15 encounters not recorded by the visual network. Both resident and Bigg’s (transient) transient whale groups were recorded, although analysis of vocalizations determined that the majority of the encounters recorded acoustically were of northern resident killer whales. This may be a function of life history, with Bigg’s killer whales typically noted to be less acoustically active, or could represent greater site use by this group. This first use of acoustic monitoring over the winter, complemented with visual data, can establish a better understanding of year-round use of this area by killer whales and has broader application to other sites.

Martin, S.B. and P.A. Cott

Journal of Great Lakes Research 42: 248-255 (2016)

DOI: 10.1016/j.jglr.2015.09.012

Most recent research and monitoring of under-water “soundscapes” has focused on marine systems in open water conditions. Here we present the first long-term assessment of the diel and seasonal patterns of a fresh-water aquatic soundscape under-ice cover. Acoustic data recorded in Yellowknife Bay, Great Slave Lake in Canada's Northwest Territories, measured the under-ice soundscape near an ice road and airport. From December to late January, the soundscape consisted of geophony from ice cracking and anthrophony from snowmobiles, aircraft, and road vehicles. In late January, burbot spawning calls began and added a localized biophony source to the soundscape that increased the total sound pressure level due to an increase in sound levels in the 10–425 Hz frequency band. The median 1 min root-mean-square sound pressure level (rms SPL) in the period without burbot biophony was 90.3 dB re 1 μPa. The measured hourly rms SPL was negatively correlated with air temperature in the 200–800 Hz band but positively correlated with average hourly wind speed in the 800–8000 Hz band. The nightly mean rms SPL was 88 dB re 1 μPa and increased to 96 dB re 1 μPa in late afternoon. This diel cycle had a strong positive correlation with the number of minutes per hour where ice-road vehicles were detected. Further work is recommended to quantify the soundscape in deep-water areas of large lakes and to include particle motion. Such information will enable the assessment of cumulative impacts of anthrophony and geophony on aquatic biota.

Frouin-Mouy, H., X. Mouy, B. Martin, and D. Hannay

Marine Mammal Science 32: 141-160 (2016)

DOI: 10.1111/mms.12246

Bearded seal (Erignathus barbatus) calls were recorded using autonomous passive acoustic recorders deployed in the northeastern Chukchi Sea between October 2007 and October 2010. Continuous acoustic data were acquired during summer (August to mid-October), and overwinter data (mid-October through July) were acquired on a duty cycle of 40/48 min every 4 h. We investigated the spatio-temporal distribution and acoustic behavior of vocalizing bearded seals in this multiyear data set. Peaks in calling occurred in spring, coinciding with the mating period, and calls stopped abruptly in late June/early July. Fewer calls were detected in summer, and the vocal presence of seals increased with the formation of pack ice in winter. Vocal activity was higher at night than during the day, with a peak around 0400 (AKST). Monthly patterns in proportional use of each call type and call duration were examined for the first time. The proportion and duration of AL1(T) and AL2(T) call types increased during the mating period, suggesting that males advertise their breeding condition by producing those specific longer trills. The observed seasonal and diel trends were consistent between years. These results improve our understanding of occurrence and acoustic behavior of bearded seals across the northeastern Chukchi Sea.