Difference between revisions of "Acoustic monitoring of marine mammals"

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Amongst the marine mammals especially the members of the two orders Pinnipedia (seals) and Cetacea (whales) have evolved an acute sense of hearing and use sound also for communication purposes. Moreover numerous toothed whale species are also capable of using echolocation to detect and characterise their food, navigate in their under water environment and to avoid obstacles. The transmission of sound is the most efficient form of information transfer underwater both for the animals to communicate and orient in their underwater environment but also for us to detect and localise the animals themselves by using active and passive acoustic detection methods. The acoustic characteristics of the sound emissions of marine mammals can differ considerably, ranging from very short pulsed echolocation clicks to long lasting frequency modulated songs (e.g. [http://www.birds.cornell.edu/brp/listen-to-project-sounds/listen-to-sounds]).  
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This article explains how we can monitor marine mammals by acoustic methods. This article  provides an example of [[remote sensing]] by airplane and of the application of acoustic underwater methods.  
  
Due to their mainly submerged lifestyle it is difficult to assess the movements and habitat use of whales and seals. To monitor their movements as well as their abundance and density in a selected area over time it is important to chose the appropriate methods.
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==Introduction==
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Marine mammals, especially members of the two orders Pinnipedia (seals) and Cetacea (whales), have evolved an acute sense of hearing as well as the ability to use sound for communication purposes. Moreover, numerous species of toothed whales are capable of using echolocation to detect and characterize their food, to navigate underwater and to avoid obstacles. The transmission of sound is the most efficient form of underwater information transfer not only for the animals to communicate and orient themselves in their submarine environment, but also for researchers to detect and localize the animals through active and passive acoustic detection methods. The acoustic characteristics of sound emissions of marine mammals can differ considerably, ranging from very short pulsed echolocation clicks to long-lasting frequency modulated songs (see e.g. <ref> [http://www.birds.cornell.edu/brp/listen-to-project-sounds/listen-to-sounds Website to listen to sounds]</ref>). Due to their mainly submerged lifestyle, it is difficult to assess the movements and habitat uses of whales and seals. To monitor their movements as well as their abundance and density in selected areas over time, it is important to choose the appropriate methods.
  
The abundance and distribution of marine mammals can best be assessed by applying line transect distance sampling methods and analysis techniques (e.g. [http://www.ruwpa.st-and.ac.uk/distance/]) on data gathered from either visual observation above the surface (land-based from an elevated point on the shore, ship-based or from an airplane) or by using acoustic detectors underwater.
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[[image:lucke_1.jpg|thumb|350px|left|'''Figure 1''': A typical airplane (Partenavia 68) used for surveys with high wings and bubble windows allowing a good view onto the track line under the plane. (Picture: FTZ Westküste)]]
  
[[image:lucke1.jpg|thumb|right|caption A typical airplane (Partenavia 68) used for surveys with high wings and bubble windows allowing a good view onto the track line under the plane. (Picture: FTZ Westküste)]]
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==Monitoring of marine mammals==
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The abundance and distribution of marine mammals can best be assessed by line transect distance sampling methods and corresponding analyses techniques (e.g. <ref> [http://www.ruwpa.st-and.ac.uk/distance/ Distance home page]</ref>). Data can be gathered from by visual observation above the surface (land-based from an elevated point on the shore, ship-based or from an aircraft) or by using passive hydro-acoustic detectors.
  
The detection of sounds emitted underwater by the marine mammals is done by using hydrophones (e.g. [http://www.unipv.it/webcib/edu_underwaterbioacoustics_uk.html#sdet]). Usually two or more hydrophones are being towed in an array as the time difference of arrival of the individual sounds at the spatially separated hydrophones allows to triangulate and analyse for bearing of the received sound and thereby to locate the sound source.  
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[[image:lucke_2.jpg|thumb|right|frame|'''Figure 2''': Harbour porpoises sighting from a sailing boat and underwater deployment of a T-POD underwater to detect their presence by monitoring their acoustic emissions. (Picture: Harald Benke, Deutsches Meeresmuseum)]]
The acoustic sensitivity of the receiver and the width of the hydrophones frequency spectrum in relation to the ambient noise define the detection range of the hydrophones and the variety of marine mammals that be detected with it. The receiving hydrophones are either being towed behind a vessel ([http://www.unipv.it/webcib/edu_underwaterbioacoustics_uk.html]) or deployed as stationary hydrophones (SOSUS:
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[http://www.pmel.noaa.gov/vents/acoustics/whales/bioacoustics.html]
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Hydrophones allow detection of sounds emitted underwater by the marine mammals (e.g. <ref> [http://www.unipv.it/webcib/edu_underwaterbioacoustics_uk.html#sdet Sound detection]</ref>).  
[http://www.news.cornell.edu/releases/Feb05/AAAS.Clark.deb.html], T-PODs: [http://www.chelonia.co.uk/][http://www.aquatecgroup.com/appsmarine.html]). Usually a specialised sound recognition software is needed to identify to which species the recorded sounds can be attributed to.
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The sensitivity of these acoustic receivers and the bandwidth of the hydrophones' frequency spectrum in relation to the ambient noise, define the detection range of the hydrophones and hence the variety of marine mammals it can detect. The receiving hydrophones are either being towed behind a vessel (<ref>[http://www.unipv.it/webcib/edu_underwaterbioacoustics_uk.html Introduction of underwater bioacoustics]</ref>) or deployed as stationary hydrophones (SOSUS <ref>[http://www.pmel.noaa.gov/vents/acoustics/whales/bioacoustics.html Monitoring marine mammals using acoustics]</ref> <ref>[http://www.news.cornell.edu/releases/Feb05/AAAS.Clark.deb.html Cornell News about whales]</ref>, T-PODs (<ref>[http://www.chelonia.co.uk/ Acoustic monitoring of cetaceans]</ref> <ref>[http://www.aquatecgroup.com/appsmarine.html Project of the Aquatic Group within the marine mammal community]</ref>). When towed, usually two or more hydrophones are installed in an array. The time difference of arrival of the animals' individual sounds at the spatially separated hydrophones allows to triangulate and analyse a bearing of the received sound, thereby locating its sound source. Usually special sound recognition software is needed to identify the species to which the recorded sounds can be attributed to.
With decreasing size of the technical acoustic components it is possible to deploy sound recording systems on the marine mammals to monitor their acoustic emissions simultaneously to the sound immissions received by them. In combination with satellite tags and data loggers (D-tag: [http://www.whoi.edu/oceanus/viewArticle.do?id=3820], A-tag: [http://cse.fra.affrc.go.jp/akamatsu/en/05publications/JASA1.htm]) this new approach allows to follow the animals movements and to analyse its behaviour in relation to environmental parameters in retrospect using dead reckoning methods ([http://www.rolexawards.com/laureates/laureate-89-wilson.html]).
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With decreasing the size of the technical acoustic components, it is possible to deploy sound recording systems on marine mammals in order to monitor their acoustic emissions simultaneously to sound emissions received by them. In combination with satellite transmitters and archival data loggers (D-tag <ref> [http://www.whoi.edu/oceanus/viewArticle.do?id=3820 Playing tag with whales]</ref>, A-tag <ref>[http://cse.fra.affrc.go.jp/akamatsu/en/05publications/JASA1.htm Wider Angle Sonar than Expected]</ref>), this new approach allows one to follow the animals' movements and to analyse their behaviour in relation to environmental parameters in retrospect due to dead reckoning methods.
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==See also==
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===Internal links===
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* [[General principles of optical and acoustical instruments]]
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* [[Currents and turbulence by acoustic methods]]
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* [[Acoustic backscatter profiling sensors (ABS)]]
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* [[Acoustic point sensors (ASTM, UHCM, ADV)]]
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* [[Marine mammals' health as an indicator of ecosystem health - tools for monitoring]]
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* [[Counting seabirds from ships and aircraft]]
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* [[Application of data loggers to seabirds]]
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===Further reading===
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* '''Monitoring:''' G.W. GARNER, S.C. AMSTRUP, J.L. LAAKE, B.F.J. MANLY, L.L. MCDONALD & D.G. ROBERTSON (Eds.) (1999): Marine Mammal Survey and Assessment Methods. A.A.Balkema, Rotterdam and Brookfield.
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* '''Distance Sampling:''' S.T. BUCKLAND, D.R. ANDERSON, K.P. BURNHAM, J.L. LAAKE, D.L. BORCHERS & L. THOMAS (2001). Introduction to Distance Sampling: Estimating abundance of Biological Populations. Oxford University Press, Oxford, UK.
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* '''Marine Mammal Ecology:''' J.E. Reynolds, III. & S.A. Rommel (Eds.) (1999). Biology of Marine Mammals. Smithsonian Institution Press, Washington and London.
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* '''Marine Mammal Acoustics:''' W.J. RICHARDSON, C.R. JR GREENE, C.I. MALME & D.H. THOMSON (1995). Marine Mammals and Noise. London: Academic Press.
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==References==
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<references/>
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{{author
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|AuthorID=14122
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|AuthorFullName=Klaus Lucke
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|AuthorName=Lucke}}
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[[Category:Coastal and marine observation and monitoring]]
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[[Category:Observation of biological parameters]]

Revision as of 15:59, 29 June 2019

This article explains how we can monitor marine mammals by acoustic methods. This article provides an example of remote sensing by airplane and of the application of acoustic underwater methods.

Introduction

Marine mammals, especially members of the two orders Pinnipedia (seals) and Cetacea (whales), have evolved an acute sense of hearing as well as the ability to use sound for communication purposes. Moreover, numerous species of toothed whales are capable of using echolocation to detect and characterize their food, to navigate underwater and to avoid obstacles. The transmission of sound is the most efficient form of underwater information transfer not only for the animals to communicate and orient themselves in their submarine environment, but also for researchers to detect and localize the animals through active and passive acoustic detection methods. The acoustic characteristics of sound emissions of marine mammals can differ considerably, ranging from very short pulsed echolocation clicks to long-lasting frequency modulated songs (see e.g. [1]). Due to their mainly submerged lifestyle, it is difficult to assess the movements and habitat uses of whales and seals. To monitor their movements as well as their abundance and density in selected areas over time, it is important to choose the appropriate methods.

Figure 1: A typical airplane (Partenavia 68) used for surveys with high wings and bubble windows allowing a good view onto the track line under the plane. (Picture: FTZ Westküste)

Monitoring of marine mammals

The abundance and distribution of marine mammals can best be assessed by line transect distance sampling methods and corresponding analyses techniques (e.g. [2]). Data can be gathered from by visual observation above the surface (land-based from an elevated point on the shore, ship-based or from an aircraft) or by using passive hydro-acoustic detectors.

Figure 2: Harbour porpoises sighting from a sailing boat and underwater deployment of a T-POD underwater to detect their presence by monitoring their acoustic emissions. (Picture: Harald Benke, Deutsches Meeresmuseum)

Hydrophones allow detection of sounds emitted underwater by the marine mammals (e.g. [3]). The sensitivity of these acoustic receivers and the bandwidth of the hydrophones' frequency spectrum in relation to the ambient noise, define the detection range of the hydrophones and hence the variety of marine mammals it can detect. The receiving hydrophones are either being towed behind a vessel ([4]) or deployed as stationary hydrophones (SOSUS [5] [6], T-PODs ([7] [8]). When towed, usually two or more hydrophones are installed in an array. The time difference of arrival of the animals' individual sounds at the spatially separated hydrophones allows to triangulate and analyse a bearing of the received sound, thereby locating its sound source. Usually special sound recognition software is needed to identify the species to which the recorded sounds can be attributed to.

With decreasing the size of the technical acoustic components, it is possible to deploy sound recording systems on marine mammals in order to monitor their acoustic emissions simultaneously to sound emissions received by them. In combination with satellite transmitters and archival data loggers (D-tag [9], A-tag [10]), this new approach allows one to follow the animals' movements and to analyse their behaviour in relation to environmental parameters in retrospect due to dead reckoning methods.

See also

Internal links

Further reading

  • Monitoring: G.W. GARNER, S.C. AMSTRUP, J.L. LAAKE, B.F.J. MANLY, L.L. MCDONALD & D.G. ROBERTSON (Eds.) (1999): Marine Mammal Survey and Assessment Methods. A.A.Balkema, Rotterdam and Brookfield.
  • Distance Sampling: S.T. BUCKLAND, D.R. ANDERSON, K.P. BURNHAM, J.L. LAAKE, D.L. BORCHERS & L. THOMAS (2001). Introduction to Distance Sampling: Estimating abundance of Biological Populations. Oxford University Press, Oxford, UK.
  • Marine Mammal Ecology: J.E. Reynolds, III. & S.A. Rommel (Eds.) (1999). Biology of Marine Mammals. Smithsonian Institution Press, Washington and London.
  • Marine Mammal Acoustics: W.J. RICHARDSON, C.R. JR GREENE, C.I. MALME & D.H. THOMSON (1995). Marine Mammals and Noise. London: Academic Press.

References

The main author of this article is Klaus Lucke
Please note that others may also have edited the contents of this article.

Citation: Klaus Lucke (2019): Acoustic monitoring of marine mammals. Available from http://www.coastalwiki.org/wiki/Acoustic_monitoring_of_marine_mammals [accessed on 28-03-2024]