Demonstrating the feasibility of near-real-time vessel noise mapping to manage marine mammal noise impacts (PDF)

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.

Effects of 2D seismic on the snow crab fishery (PDF)

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.

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

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.

Maximum likelihood estimators and Cramér-Rao bound for estimating azimuth and elevation angles using compact arrays (PDF)

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.

Seasonal trends in acoustic detection of marine mammals in Baffin Bay and Melville Bay, Northwest Greenland (PDF)

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.

Underwater noise from geotechnical drilling and standard penetration testing (PDF)

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.

Automatic grunt detector and recognizer for Atlantic cod (Gadus morhua) (PDF)

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.

Behavioural responses of western gray whales to a 4-D seismic survey off northeastern Sakhalin Island, Russia (PDF)

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.

Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea (PDF)

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.

COMPILE—A generic benchmark case for predictions of marine pile-driving noise

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.

Gray whale densities during a seismic survey off Sakhalin Island, Russia (PDF)

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.

Modeling the aggregated exposure and responses of bowhead whales Balaena mysticetus to multiple sources of anthropogenic underwater sound (PDF)

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.

Quantitative classification of harbor seal breeding calls in Georgia Strait, Canada (PDF)

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.

Short- and long-term monitoring of underwater sound levels in the Hudson River (New York, USA) (PDF)

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.

The combined use of visual and acoustic data collection techniques for winter killer whale (Orcinus orca) observations (PDF)

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.

The under-ice soundscape in Great Slave Lake near the city of Yellowknife, Northwest Territories, Canada (PDF)

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.

Underwater acoustic behavior of bearded seals (Erignathus barbatus) in the northeastern Chukchi Sea, 2007–2010 (PDF)

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.

Bayesian environmental inversion of airgun modal dispersion using a single hydrophone in the Chukchi Sea (PDF)

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

Journal of the Acoustical Society of America 137: 3009-3023 (2015)

DOI: 10.1121/1.4921284

This paper presents estimated water-column and seabed parameters and uncertainties for a shallow-water site in the Chukchi Sea, Alaska, from trans-dimensional Bayesian inversion of the dispersion of water-column acoustic modes. Pulse waveforms were recorded at a single ocean-bottom hydrophone from a small, ship-towed airgun array during a seismic survey. A warping dispersion time-frequency analysis is used to extract relative mode arrival times as a function of frequency for source-receiver ranges of 3 and 4 km which are inverted for the water sound-speed profile (SSP) and subbottom geoacoustic properties. The SSP is modeled using an unknown number of sound-speed/depth nodes. The subbottom is modeled using an unknown number of homogeneous layers with unknown thickness, sound speed, and density, overlying a halfspace. A reversible-jump Markov-chain Monte Carlo algorithm samples the model parameterization in terms of the number of water-column nodes and subbottom interfaces that can be resolved by the data. The estimated SSP agrees well with a measured profile, and seafloor sound speed is consistent with an independent headwave arrival-time analysis. Environmental properties are required to model sound propagation in the Chukchi Sea for estimating sound exposure levels and environmental research associated with marine mammal localization.

Distance from shore as an indicator of disturbance of gray whales during a seismic survey off Sakhalin Island, Russia (PDF)

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

Endangered Species Research 29: 161-178 (2015)

DOI: 10.3354/esr00701

A seismic survey was conducted adjacent to the nearshore feeding ground of gray whales Eschrichtius robustus off northeastern Sakhalin Island, Russia. Scan surveys were conducted at 7 shore stations before, during and after the seismic survey. We investigated whether gray whales shifted their distribution with respect to distance from the shoreline in response to acoustic pulses from the seismic source. To do this, we used linear mixed effects modelling that included effects of detection, space and time. Data were tested for effects of magnitude and presence/absence of sound from seismic activity on whale distance from shore. Sound covariates were estimated over 3 temporal scales (8 h, 3 d and since the start of seismic activity) at locations 500 and 5000 m offshore each observation station. Sighting distance from shore was less in poor visibility and at earlier times of day. No significant effects of sound were identified, although data suggest that at most stations, sighting distance from shore increased slightly over the 2 wk of the seismic survey. The analysis was limited, however, by several factors that included low numbers of sightings throughout most of the study, non-availability of data on biomass of gray whale prey and sources of error that could not be accounted for in the model. Sensitivity to potential errors in sighting distance estimation was assessed using a correction factor based on known locations of vessels and gray whales when sighted. The model was refitted using distance-corrected sightings. Results were consistent with the original model.

Monitoring and impact mitigation during a 4D seismic survey near a population of gray whales off Sakhalin Island, Russia (PDF)

Bröker, K., G. Gailey, J. Muir, and R. Racca

Endangered Species Research 28: 187-208 (2015)

DOI: 10.3354/esr00670

A 4D seismic survey was conducted in 2010 near the feeding grounds of gray whales off Sakhalin Island, Russia. To minimize disruptions to the whales’ feeding activity and enhance understanding of the potential impacts of seismic surveys on gray whales Eschrichtius robustus, an extensive monitoring and mitigation plan (MMP) was developed. Typically, mitigation plans involve observers on seismic vessels to monitor for the presence of marine mammals in an exclusion zone so as to prevent physical injury to the animals. Due to the protected status of western gray whales, an additional protection zone based on a behavioural disturbance threshold of exposure of 156 dB re μPa2-s per pulse was applied for whales within their feeding habitat defined by the estimated 95% abundance contour. Real-time radio-transmitting acoustic recorders were deployed along this contour to verify modelled acoustic footprints within the feeding grounds. Shore- and vessel-based observation teams monitored for the presence and activity of whales. A real-time GIS workflow tracking procedure was developed that integrated acoustic and whale positioning data to determine if sound levels at a whales’ position within the feeding area exceeded the behavioural threshold, in which case a shut-down of the seismic source was implemented. Additionally, behaviour and distribution surveys were conducted before, during and after the seismic survey to evaluate the effectiveness of the MMP. No large changes in whale movement, respiration, or distribution patterns were observed during the seismic survey. This could be interpreted to mean that the MMP was effective in reducing the sound exposure and behavioural responses of gray whales to seismic sounds.