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    Target strengths of Antarctic krill (Euphausia superba) at 38 and 120 kHz

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    JAS000016.pdf (1.342Mb)
    Date
    1990-01
    Author
    Foote, Kenneth G.  Concept link
    Everson, Inigo  Concept link
    Watkins, Jonathan L.  Concept link
    Bone, Douglas G.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/5649
    As published
    https://doi.org/10.1121/1.399282
    DOI
    10.1121/1.399282
    Abstract
    Encaged aggregations of live krill in good to pristine condition have been ensonified at 38 and 120 kHz. Concurrent underwater television observations of behavior resemble those made by underwater divers in naturally occurring swarms, with comparably high densities of the order of 104 animals/m3 . Mean, single‐animal target strengths have been inferred from measurements of echo energy. For aggregations with mean lengths in the range [30,39] mm, the mean single‐krill target strengths are in the range [−88,−83] dB at 38 kHz and [−81,−74] dB at 120 kHz. Collateral measurements on some of the same encaged specimens determined a density contrast of 1.0357±0.0067 and sound‐speed contrast of 1.0279±0.0024, relative to seawater. These numbers have been used with the fluid‐sphere model as stated by Greenlaw [Limnol. Oceanogr. 24, 226–242 (1979)] . Computed backscattering cross sections have been averaged over the length distributions of each measured aggregation, resulting in target strength predictions in the range [−86,−80] dB at 38 kHz and [−79,−76] dB at 120 kHz.
    Description
    Author Posting. © Acoustical Society of America, 1990. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 87 (1990): 16-24, doi:10.1121/1.399282.
    Collections
    • Applied Ocean Physics and Engineering (AOP&E)
    Suggested Citation
    Journal of the Acoustical Society of America 87 (1990): 16-24
     
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