Nathalie Roy

Fisheries and Oceans Canada, Ottawa, Ontario, Canada

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Publications (20)15.44 Total impact

  • Yvan Simard · Nathalie Roy · Cédric Gervaise · Samuel Giard
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    ABSTRACT: A setup for measuring spectral source levels (SSLs) of ships transiting along a seaway, the traffic density and shipping noise, is presented. The results feed shipping-noise modeling that reproduces the actual in situ observations to map shipping-noise variability over space and time for investigating its effects on aquatic organisms. The ship's SSL databank allows sorting the different contributors to total shipping noise for assisting in exploring mitigation approaches (e.g., fleet composition, rerouting). Such an acoustic observatory was deployed since November 2012 for a complete annual cycle of measurements in the deep downstream part of the St. Lawrence Seaway.
    No preview · Article · Nov 2015 · Advances in Experimental Medicine and Biology
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    ABSTRACT: A three-dimensional circulation model, coupled to a Lagrangian particle drift model, is used to understand the processes leading to krill transport from the northwest Gulf of St. Lawrence (nwGSL) towards the head of the Lower St. Lawrence Estuary (LSLE), a well-known site of krill accumulation. An analysis of the circulation at the scale of the Gulf of St. Lawrence (GSL) over five years (2006 to 2010) evidenced four major findings. (i) There are two main seasonal circulation patterns, one in winter–spring and one in summer–fall, driven by local wind forcing and transport at Cabot Strait and at the Strait of Belle Isle. (ii) The freshwater runoff variability does not control the observed inflow events at the mouth of the LSLE. (iii) Extratropical storms passing over the GSL are important for the transport of krill into the LSLE through the generation of inflow events at Pointe-des-Monts. (iv) The contribution of the transport in the surface layer (where krill are found at night) during these inflow events is also important in modulating the variability of the transport of krill into the LSLE. The inflow events, combined with the presence or absence of high krill densities in the nwGSL, partly control the interannual variability of the transport of krill into the LSLE
    Full-text · Article · Oct 2015 · Atmosphere-ocean
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    ABSTRACT: Mapping vessel noise is emerging as one method of identifying areas where sound exposure due to shipping noise could have negative impacts on aquatic ecosystems. The probability distribution function (pdf) of sound exposure levels (SEL) is an important metric for identifying areas of concern. In this paper a probabilistic shipping SEL modeling method is described to obtain the pdf of SEL using the sonar equation and statistical relations linking the pdfs of ship traffic density, source levels, and transmission losses to their products and sums.
    Full-text · Article · Jun 2015 · The Journal of the Acoustical Society of America
  • Yvan Simard · Nathalie Roy · Samuel Giard · Mehmet Yayla
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    ABSTRACT: http://www.dfo-mpo.gc.ca/Library/352593.pdf The Automatic Identification System (AIS) ship-tracking data collected by Fisheries and Oceans Canada’s (DFO) Canadian Coast Guard (CCG) in southern Canadian waters were used to map traffic density throughout 2013. The region considered in this report is eastern Canadian marine waters east of Ile d’Orléans near Québec City in the St. Lawrence Estuary. The AIS traffic maps are provided for the whole year and by month. For each time period, maps of daily traffic density are provided for all vessel traffic and selectively for seven vessel types, five vessel length classes, and five sailing speed classes. The data were binned using a common metric of ship-h per 1 × 1 km grid cell per day for all maps. The cumulative histogram of traffic density, total area with traffic, and the sum of daily traffic density are provided for each map. The atlas contains a total of 299 traffic maps. Les données du système AIS (Automatic Identification System) de suivi de la navigation maritime récoltées par la Garde Côtière canadienne du ministère des Pêches et des Océans (MPO) dans les eaux méridionales canadiennes sont utilisées pour cartographier l’intensité du trafic au cours de 2013. La région considérée dans ce rapport est celle des eaux marines canadiennes à l’est de l’Ile d’Orléans, près de Québec dans l’estuaire du Saint-Laurent. Les cartes du trafic AIS sont fournies pour l’année entière ainsi que par mois. Pour chaque période, les cartes sont fournies pour le trafic total ainsi que séparément pour sept types de navires, cinq classes de longueur de navire et cinq classes de vitesse de transit. Une métrique commune, navire-h par cellule de 1 × 1 km par jour, est utilisée pour toutes les cartes. L’histogramme cumulé de la densité du trafic, l’aire totale avec trafic et la somme du trafic quotidien sont fournis pour chaque carte. L’atlas renferme un total de 299 cartes de trafic.
    No preview · Chapter · Jan 2014
  • Yvan Simard · Nathalie Roy · Samuel Giard · Mehmet Yayla
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    ABSTRACT: The Automatic Identification System (AIS) ship-tracking data collected by Fisheries and Oceans Canada’s (DFO) Canadian Coast Guard (CCG) in southern Canadian waters were used to map traffic density throughout 2013. The region considered in this report is the Great Lakes and upper St. Lawrence fresh waters, west of the eastern end of Ile d’Orléans near Québec City in the St. Lawrence estuary. The AIS traffic maps are provided for the whole year and by month. For each time period, maps of daily traffic density are provided for all vessel traffic and selectively for seven vessel types, five vessel length classes, and five sailing speed classes. The data were binned using a common metric of ship-h per 1 × 1 km grid cell per day for all maps. The cumulative histogram of traffic density, total area with traffic, and the sum of daily traffic density are provided for each map. The atlas contains a total of 299 traffic maps. Les données du système AIS (Automatic Identification System) de suivi de la navigation maritime récoltées par la Garde Côtière canadienne du ministère des Pêches et des Océans (MPO) dans les eaux méridionales canadiennes sont utilisées pour cartographier l’intensité du trafic au cours de 2013. La région considérée dans ce rapport est celle des Grands Lacs et des eaux douces à l’ouest de de la pointe est de l’Ile d’Orléans, près de Québec dans l’estuaire du Saint-Laurent. Les cartes du trafic AIS sont fournies pour l’année entière ainsi que par mois. Pour chaque période, les cartes sont fournies pour le trafic total ainsi que séparément pour sept types de navires, cinq classes de longueur de navire et cinq classes de vitesse de transit. Une métrique commune, navire-h par cellule de 1 × 1 km par jour, est utilisée pour toutes les cartes. L’histogramme cumulé de la densité du trafic, l’aire totale avec trafic et la somme du trafic quotidien sont fournis pour chaque carte. L’atlas renferme un total de 299 cartes de trafic.
    No preview · Chapter · Jan 2014
  • Yvan Simard · Nathalie Roy · Samuel Giard · Mehmet Yayla
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    ABSTRACT: http://www.dfo-mpo.gc.ca/Library/352600.pdf The Automatic Identification System (AIS) ship-tracking data collected by Fisheries and Oceans Canada’s (DFO) Canadian Coast Guard (CCG) in southern Canadian waters were used to map traffic density throughout 2013. The region considered in this report is the West Coast. The AIS traffic maps are computed for the whole year and by month. The AIS traffic maps are provided for the whole year and by month. For each time period, maps of daily traffic density are provided for all vessel traffic and selectively for seven vessel types, five vessel length classes, and five sailing speed classes. The data were binned using a common metric of ship-h per 1 × 1 km grid cell per day for all maps. The cumulative histogram of traffic density, total area with traffic, and the sum of daily traffic density are provided for each map. The atlas contains a total of 299 traffic maps. Les données du système AIS (Automatic Identification System) de suivi de la navigation maritime récoltées par la Garde Côtière canadienne du ministère des Pêches et des Océans (MPO) dans les eaux méridionales canadiennes sont utilisées pour cartographier l’intensité du trafic au cours de 2013. La région considérée dans ce rapport est celle de la Côte Ouest. Les cartes du trafic AIS sont fournies pour l’année entière ainsi que par mois. Pour chaque période, les cartes sont fournies pour le trafic total ainsi que séparément pour sept types de navires, cinq classes de longueur de navire et cinq classes de vitesse de transit. Une métrique commune, navire-h par cellule de 1 × 1 km par jour, est utilisée pour toutes les cartes. L’histogramme cumulé de la densité du trafic, l’aire totale avec trafic et la somme du trafic quotidien sont fournis pour chaque carte. L’atlas renferme un total de 299 cartes de trafic.
    No preview · Chapter · Jan 2014

  • No preview · Article · Dec 2012
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    ABSTRACT: A continuous car ferry line crossing the Saguenay Fjord mouth and traffic from the local whale-watching fleet introduce high levels of shipping noise in the heart of the Saguenay-St. Lawrence Marine Park. To characterize this noise and examine its potential impact on belugas, a 4-hydrophone array was deployed in the area and continuously recorded for five weeks in May-June 2009. The source levels of the different vessel types showed little dependence on vessel size or speed increase. Their spectral range covered 33 dB. Lowest noise levels occurred at night, when ferry crossing pace was reduced, and daytime noise peaked during whale-watching tour departures and arrivals. Natural ambient noise prevailed 9.4% of the time. Ferry traffic added 30-35 dB to ambient levels above 1 kHz during crossings, which contributed 8 to 14 dB to hourly averages. The whale-watching fleet added up to 5.6 dB during peak hours. Assuming no behavioral or auditory compensation, half of the time, beluga potential communication range was reduced to less than ~30% of its expected value under natural noise conditions, and to less than ~15% for one quarter of the time, with little dependence on call frequency. The echolocation band for this population of belugas was also affected by the shipping noise.
    Full-text · Article · Jul 2012 · The Journal of the Acoustical Society of America
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    ABSTRACT: Passive acoustic monitoring (PAM) of marine mammal vocalizations has been efficiently used in a wide set of applications ranging from marine wildlife surveys to risk mitigation of military sonar emissions. The primary use of PAM is for detecting bioemissions, a good proportion of which are impulse sounds or clicks. A click detection algorithm based on kurtosis estimation is proposed as a general automatic click detector. The detector works under the assumption that click trains are embedded in stochastic but Gaussian noise. Under this assumption, kurtosis is used as a statistical test for detection. The algorithm explores acoustic sequences with the optimal frequency bandwidth for focusing on impulse sounds. The detector is successfully applied to field observations, and operates under weak signal to noise ratios and in presence of stochastic background noise. The algorithm adapts to varying click center frequency. Kurtosis appears as a promising approach to detect click trains, alone or in combination with other clicks detector, and to isolate individual clicks.
    No preview · Article · Nov 2010 · Applied Acoustics
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    ABSTRACT: A passive acoustic method is developed to estimate whale density from their calling activity in a monitored area. The algorithm is applied to a loquacious species, the white whale (Delphinapterus leucas), in Saguenay fjord mouth near Tadoussac, Canada, which is severely affected by shipping noise. Beluga calls were recorded from cabled coastal hydrophones deployed in the basin while the animal density was estimated visually from systematic observations from a fixed-point on the shore. Beluga calling activity was estimated from an algorithm extracting the call events in time–frequency space, while simultaneously tracking the masking intensity resulting from local shipping noise. The activity index was summarized in 15- and 30-min bins using four different metrics. For bins containing more than 40% of valid data, the metrics were compared to the corresponding visual observations. The estimated mean acoustic detection range generally exceeded the fjord width, and extended to the whole ∼3-km long monitored area under low-noise conditions. The significant linear relations of the visual estimates with the calling activity metrics allowed assessing expected number of visually detected belugas in the basin from a weighted regression model, with a mean standard error of 7.1%.
    No preview · Article · Nov 2010 · Applied Acoustics
  • Nathalie Roy · Yvan Simard · Cédric Gervaise
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    ABSTRACT: A simple passive acoustic monitoring (PAM) setup was used to localize and track beluga whales underwater in three dimensions (3D) in a fjord. In June 2009, beluga clicks were recorded from a cabled hydrophone array in a regularly frequented habitat in Eastern Canada. Beluga click energy was concentrated in the 30–50 kHz frequency band. The click trains detected on several hydrophones were localized from their time difference of arrivals. Cluster analysis linked localizations into tracks based on criteria of spatial and temporal proximity. At close ranges from the array, the localized click-train series allowed three-dimensional tracking of a beluga during its dive. Clicks within a train spanned a large range of durations, inter-click intervals, source levels and bandwidths. Buzzes sometimes terminated the trains. Repeated click packets were frequent. All click characteristics are consistent with oblique observations from the beam axis, and ordered variation of the source pattern during a train, likely resulting from a scan of angles from the beam axis, was observed before click trains indicated focusing of the echolocation clicks in one direction. The click-train series is interpreted as echolocation chasing for preys during a foraging dive. Results show that a simple PAM system can be configured to passively and effectively 3D track wild belugas and small odontocetes in their regularly frequented habitat.
    No preview · Article · Nov 2010 · Applied Acoustics
  • Yvan Simard · Nathalie Roy · Cédric Gervaise
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    ABSTRACT: The performance of large-aperture hydrophone arrays to detect and localize blue and fin whales' 15-85 Hz signature vocalizations under ocean noise conditions was assessed through simulations from a normal mode propagation model combined to noise statistics from 15 960 h of recordings in Saguenay-St. Lawrence Marine Park. The probability density functions of 2482 summer noise level estimates in the call bands were used to attach a probability of detection/masking to the simulated call levels as a function of whale depth and range for typical environmental conditions. Results indicate that call detection was modulated by the calling depth relative to the sound channel axis and by modal constructive and destructive interferences with range. Masking of loud infrasounds could reach 40% at 30 km for a receiver at the optimal depth. The 30 dB weaker blue whale D-call were subject to severe masking. Mapping the percentages of detection and localization allowed assessing the performance of a six-hydrophone array under mean- and low-noise conditions. This approach is helpful for optimizing hydrophone configuration in implementing passive acoustic monitoring arrays and building their detection function for whale density assessment, as an alternative to or in combination with the traditional undersampling visual methods.
    No preview · Article · Jul 2008 · The Journal of the Acoustical Society of America
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    ABSTRACT: Passive acoustic monitoring (PAM) was used to generate a six-week continuous time-series of occupation of a segment of the St. Lawrence Estuary by belugas. The PAM data were acquired from a cabled hydrophone deployed at mid-depth into the 300-m deep Laurentian channel off Cap-de-Bon-Desir during summer 2003. Beluga vocalisation activity time-series was obtained from the [0.5-5.0 kHz] bandpassed PAM data that were processed to filter out noise from the heavy shipping on the nearby St. Lawrence Seaway and from occasional whale watching boats, and low-frequency traces of clicks, via adaptive spectral subtraction and image processing methods applied to the spectrogram. The remaining traces on the binary image of the spectrogram were summed up to generate a vocalisation index, which was essentially due to belugas in this region. The vocalisation index time-series was then analysed for presence of circadian rhythms and correlations with the semi-diurnal tidal cycle, currents from an acoustic Doppler current profiler and wind. Results are interpreted from the knowledge of the biological and physical oceanographic processes occurring in the monitored area.
    No preview · Article · Jun 2008 · The Journal of the Acoustical Society of America
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    ABSTRACT: The Saguenay fjord entrance in the St. Lawrence Estuary at Tadoussac is a world famous site where beluga and minke whales can be regularly observed from the coast. Strong tidal upwelling over the shallow sill of the fjord controls the exchanges with the St. Lawrence. In May 2005, an intensive oceanographic and acoustic survey was conducted to understand how the complex 3D hydrodynamics may contribute to concentrating whale preys. High time-space resolution acoustics (38 and 120 kHz split-beam), ADCP (acoustic Doppler current profilers), CTD profiles, plankton and micronekton sampling were used to track the 3D movements of water masses, zooplankton and forage fish. During flood, the dense cold waters that jump over the sill block the Saguenay outflow and subduct into the fjord with their fish and zooplankton content. This complex 3D circulation generates fronts and convergence zones where biomass is concentrating until current reversal occurs during ebb. These concentrations are then advected and dispersed downstream over the sill with the Saguenay surface plume. This whale prey tidal concentrating process depends on the existence of sufficient forage fish densities in the mesoscale neighbourhood. It is likely at the basis of the persistent high frequentation of this area by whales.
    No preview · Article · Jun 2008 · The Journal of the Acoustical Society of America
  • YVAN SIMARD · NATHALIE ROY · CÉDRIC GERVAISE

    No preview · Article · Jun 2008 · Bioacoustics
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    Yvan Simard · Nathalie Roy
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    ABSTRACT: The feasibility of using passive acoustic methods (PAM) to monitor time-space distribution of fin and blue whales in the Saguenay-St. Lawrence Marine Park was explored using large-aperture sparse hydrophone arrays. The arrays were deployed during summers 2003 to 2005 at the head of the 300-m deep Laurentian Channel. They were composed of 5 AURAL autonomous hydrophones moored at mid-water depths, near the summer sound channel. A small coastal array complemented the deployment in 2003. The apertures were from 20 to 40 km and the configurations were changed from year to year. The most frequent calls recorded were blue and fin whale signature infrasounds. Noise from transiting ships on the busy St. Lawrence Seaway often masked the calls on the nearest hydrophones. Sometimes this resulted in an insufficient number of receivers for localizing the whales using time difference of arrival (TDoA) methods. The technical characteristics of the arrays and data processing are presented, with an example of call detection and localization. Despite the difficulties inherent to this environment, PAM can be effectively implemented there, eventually for real-time operations.
    Preview · Article · Mar 2008
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    Nathalie Roy · Yvan Simard · Jean Rouat
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    ABSTRACT: Three algorithms are explored to localize fin whale calls recorded from a large-aperture hydrophone array deployed in the Saguenay - St. Lawrence Marine Park. The methods have to cope with varying sound speed in space and time, errors in time differences of arrival (TDoA) measurements in a noisy environment, and often a limited number of hydrophones having recorded a particular event. The array was composed of 5 AURAL autonomous hydrophones with a total aperture of about 40 km, coupled with 2 hydrophones from a small-aperture cabled coastal array. The autonomous hydrophones clock drifts were estimated with a level of uncertainty from timed sources and the coastal array time reference. The calls were then localized by constant-speed hyperbolic fixing, variable-speed isodiachron Monte-Carlo simulations, and a ray-tracing propagation model. The Monte-Carlo simulations generate clouds of possible localizations from the uncertainty in hydrophone positions, TDoAs and the effective horizontal sound speeds along the different source-hydrophone paths. The ray-tracing model produces a fixed grid of TDoAs which can then be consulted to find the likeliest positions of the whales. Results from the different methods are compared and their relative advantages or limitations are discussed.
    Full-text · Article · Mar 2008
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    ABSTRACT: An integrated system of intelligent acoustic buoys have been developed to detect, identify and localize whales in real-time in their environment and communicate this information to land-based stations or ships via satellite and Internet, and RF communications. The low-cost portable buoy network can be used as a marine mammal observatory to gather continuous space-time series of vocalizing animals over large basins, or as early warning systems for improving whale protection on navigation routes or around moving or fixed platforms during threatening high-level acoustic activity. The unit buoy is powered by two 12-V batteries connected to solar panels. The processor is an 800 MHz Pentium III PC equipped with 400-MB fast memory and a 100-GB hard disk. The clock is synchronized with the embarked GPS. Data from two georeferenced hydrophones equipped with depth and temperature sensors are flowing to a 16-bit 500-kHz A/D-DSP board. Two-way communication is through 900-MHz and an Iridium satellite modems. Specific whales target calls are detected in time-frequency domain after adaptive noise-filtration. The selected master buoy collects the precisely time-tagged detections from all units via RF communication, and locates the calling whales from hyperbolic and isodiachron-Monte Carlo fixing algorithms. A simple tracking algorithm then builds the individual tracks. All acoustic data or users' selected portions of them can be stored on the hard disk. The system is designed to accommodate future developments and be easily adapted to various tasks. It can be deployed as a drifting network or anchored to the bottom, as well as from the ice sheet. First sea trials will be in August 2006 in the St. Lawrence
    No preview · Conference Paper · Oct 2006
  • Y. Simard · N. Roy · C. Gervaise
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    ABSTRACT: The noise spectra radiated by the world tallest ocean liner, the Queen Mary II (QM2), when she sailed over the blue whale feeding ground of the Saguenay - St. Lawrence Marine Park in Sept. and Oct. 2004 are presented. Recordings for her 4 transits were made from an array of AURAL autonomous hydrophones moored at mid water depth along the navigation corridor at the head of the Laurentian channel. Typical ship noise Lloyd's mirror patterns on spectrogram generally allowed identification of the closest points of approach (CPA) to the hydrophones. The analysis of the Doppler shift of stable QM2 spectral rays allowed estimating CPA ranges and sailing speed. QM2 noise signature is characterized by several strong rays between ~100 to 500 Hz, likely from her propulsion pods. Her average noise spectra are however enclosed within the envelope of the merchant ship noise measured in the area, except for high peaks below 40 Hz and the above rays. Broadband (10-1000 Hz) rms levels varied from 121 to 136 dB re 1muPa. As for most other merchant ships, this radiated shipping noise makes a barrier masking the low-frequency vocalizations of calling blue and fin whales over a large part of the basin
    No preview · Conference Paper · Oct 2006
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    Y. Simard · M. Bahoura · N. Roy
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    ABSTRACT: The detection and localization of marine mammals using passive acoustics is explored for two critical habitats in Eastern Canada. Two-dimensional hyperbolic localization is performed on time differences of arrivals of specific calls on grids of coarsely spaced autonomous recorders and on a shore-linked coastal array of closely spaced hydrophones. Delays are computed from cross-correlation and spectrogram cross- coincidence on signals enhanced with high-frequency emphasis and noise spectral suppression techniques. The outcomes and relative performance of the two delay estimation methods are compared. The difficulties encountered under the particular conditions of these two environments are discussed for the point of view of automated localisation for monitoring whales.
    Full-text · Article · Jun 2004 · Canadian Acoustics - Acoustique Canadienne