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.

/pdf/long-term-passive-acoustic-recordings-track-the-changing-2hlwy0nsq5.pdf

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

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).

Slowing deep-sea commercial vessels reduces underwater radiated noise.

Six baleen whale species are found in the temperate western North Atlantic Ocean, with limited information existing on the distribution and movement patterns for most. There is mounting evidence of distributional shifts in many species, including marine mammals, likely because of climate-driven changes in ocean temperature and circulation. Previous acoustic studies examined the occurrence of minke (Balaenoptera acutorostrata) and North Atlantic right whales (NARW; Eubalaena glacialis). This study assesses the acoustic presence of humpback (Megaptera novaeangliae), sei (B. borealis), fin (B. physalus), and blue whales (B. musculus) over a decade, based on daily detections of their vocalizations. Data collected from 2004 to 2014 on 281 bottom-mounted recorders, totaling 35,033 days, were processed using automated detection software and screened for each species' presence. A published study on NARW acoustics revealed significant changes in occurrence patterns between the periods of 2004-2010 and 2011-2014; therefore, these same time periods were examined here. All four species were present from the Southeast United States to Greenland; humpback whales were also present in the Caribbean. All species occurred throughout all regions in the winter, suggesting that baleen whales are widely distributed during these months. Each of the species showed significant changes in acoustic occurrence after 2010. Similar to NARWs, sei whales had higher acoustic occurrence in mid-Atlantic regions after 2010. Fin, blue, and sei whales were more frequently detected in the northern latitudes of the study area after 2010. Despite this general northward shift, all four species were detected less on the Scotian Shelf area after 2010, matching documented shifts in prey availability in this region. A decade of acoustic observations have shown important distributional changes over the range of baleen whales, mirroring known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats like fixed fishing gear, shipping, and noise pollution.

https://repository.library.noaa.gov/view/noaa/25727/noaa_25727_DS1.pdf

Exploring movement patterns and changing distributions of baleen whales in the western North Atlantic using a decade of passive acoustic data

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. Analysis of AIS vessel tracking data showed that 421 of 951 (44%) piloted transits achieved speeds within one knot of the target (i.e., ≤12 knots) and 55% achieved speeds ≤13 knots. Slowdown results were compared to ‘Baseline’ noise of the same region, matched across lunar months. A local hydrophone listening station in Lime Kiln State Park, 2.3 km from the shipping lane, recorded 1.2 dB reductions in median broadband noise (10-100,000 Hz, rms) compared to the Baseline period, despite longer transit durations during the trial. Filtering for commercial vessels within 6 km radius of Lime Kiln listening station (aiming to remove confounding effects of variability in vessel numbers), and excluding small boat noise, high current and wind speed periods, median noise was reduced by 2.5 dB. The reductions were highest in the 1st decade band (-3.1 dB, 10-100 Hz) and lowest in the 4th decade band (-0.3 dB reduction, 10-100 kHz). A regional vessel noise model predicted noise for a range of traffic volume and vessel speed scenarios for a 1133 km2 ‘Slowdown region’ containing the 16 nm of the trial’s shipping lanes. A temporally and spatially-explicit simulation model was used to evaluate the changes in traffic volume and speed on SRKW in their foraging habitat within this Slowdown region. The simulation model tracked the number and magnitude of noise-exposure events that impacted each of 78 SRKW across different traffic volume-speed scenarios. These metrics were simplified to a cumulative effect termed ‘potential lost foraging time’. The model predicted that the voluntary Slowdown trial achieved 22% reduction in ‘potential lost foraging time’ for SRKW, with 40% reductions under 100% 11 knot participation. Slower vessel speeds reduced underwater noise in the Slowdown area despite longer passage times and therefore suggest this is an effective way to benefit SRKW habitat function in the vicinity of shipping lanes.

http://summit.sfu.ca/system/files/iritems1/18841/fmars-06-00344.pdf

Potential Benefits of Vessel Slowdowns on Endangered Southern Resident Killer Whales

Source localization is an important field of research with numerous applications in signal processing and wireless communications. In this paper, we present a received signal strength difference (RSSD) based method to localize a source with unknown transmit power in the presence of sensor position uncertainty. It is an efficient low complexity technique which does not require transmit power estimation as with other approaches. This eliminates the uncertainty due to signal propagation parameter variations. A constrained adaptive weighted least squares technique is presented to obtain a least squares initial estimate (LSIE) of the source location. Then, this estimate is improved using a computationally efficient modified Newton method (MNM) with adaptive weights. The bias of the proposed LSIE-MNM method and the Cramer-Rao lower bound (CRLB) of the RSSD based measurement model are derived to determine the effect of sensor position uncertainties on the source location estimate. Results are presented which show that the proposed method achieves the CRLB when the SNR is sufficiently high.

Unknown Transmit Power RSSD Based Source Localization With Sensor Position Uncertainty

The Autonomous Multichannel Acoustic Recorder (AMAR, JASCO Applied Sciences) is a sophisticated precision instrument for passive acoustic monitoring and accurate underwater sound level measurements. It can be integrated with small hydrophone arrays and non-acoustic oceanographic sensors. To date, AMARs have typically been used autonomously and deployed for a few months to a year on oceanographic moorings; however, AMARs are also capable of real-time data streaming when connected to a data telemetry system. This paper describes the capabilities and functionality of the AMAR through the example of its integration within Ocean Networks Canada's VENUS Ocean Observatory deployed off the coast of British Columbia, Canada. The recent deployment of two AMAR-based hydrophone arrays and associated non-acoustic and oceanographic sensors within the VENUS system is presented in detail. The planned research and development within the AMARs on VENUS program, as well as preliminary results on the real-time automatic detection, classification, localization, and tracking of marine mammals, are presented. The two AMARs deployed on the VENUS Ocean Observatory demonstrate that, unlike traditional underwater acoustic recorders, the AMAR can act as a hub for mini ocean observatories, capturing and transmitting both acoustic and non-acoustic sensor data in realtime. It is demonstrated that the AMAR is an effective technology that can be used in near-shore, small-scale, low-cost ocean observatories.

Autonomous Multichannel Acoustic Recorders on the VENUS Ocean Observatory

Proposed metrics for the management of underwater noise for southern resident killer whales

A passive energy based analysis of the acoustic signal from a diver is presented. The frequency components of the signal during inhaling and exhaling are investigated, as well as the periodicity of the signal features. The effect of different regulators on the power spectral density of the signals is evaluated. The energy based detection problem is formulated using the time-frequency Teager Energy Operator (TEO) as it can be used to develop an adaptive detector. To evaluate the proposed approach, experimental data is employed which was recorded in the open ocean at different ranges and depths. This data was obtained using accurate hydrophones provided by Ocean Network Canada (ONC).

Passive energy based acoustic signal analysis for diver detection

Passive source location determination is a very active research area. In this paper, we present a received signal strength difference (RSSD) source localization method based on a total least square (TLS) estimator. Due to errors in the data vector and system matrix, the least squares (LS) and weighted least squares (WLS) methods are not applicable as they produce large bias in the location estimation. Therefore, an extension of the LS methods, called total least squares (TLS) is used to solve this problem. Due to the relationship between the data vector and system matrix, a modified TLS method is presented to achieve a closed form estimate. The advantage of this approach is that it does not require transmit power estimation as with other methods, and the complexity is low. The received signal strength difference is used to eliminate uncertainties due to the signal propagation parameters. Performance results are presented which show that the performance of the proposed method comes close to achieving the Cram'er-Rao lower bound.

Efficient RSSD-Based Source Positioning with System Parameter Uncertainties

Visual presentation of the outputs from marine mammal detectors is key for efficient mining of large acoustic datasets. Operators must be able to easily navigate through large time series of detections, examine spectrograms, listen to detected sounds, and validate and compare detections for different species over time and space. The JMesh web platform has been designed with these constraints in mind. The interface is organized around three interconnected visualization panels: 1) a geographic interface displays maps showing the total number of detections for each species at all monitoring locations within an adjustable time period, 2) a detection time series plot displays temporal variations of detections for several species at a selected monitoring location, and 3) a multimedia panel allows the user to visualize spectrograms, listen to sounds and validate detections. All three panels are interactive and allow the user to navigate intuitively between them. The platform uses load balancing, microservices orchestration, shared non-relational databases, and virtualization technologies to make the infrastructure fully scalable and expandable from a single server to a resource farm composed of hundreds of hosts. JMesh can display detections from archived data or from real-time acquisition systems. Compatibility with mobile devices through the Bootstrap framework simplifies access to the data while in the field.

JMesh -- A Scalable Web-Based Platform for Visualization and Mining of Passive Acoustic Data

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