Journal Article

Using multi-angle scattered sound to size fish swimbladders

Jules S. Jaffe

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 63, issue 8, pages 1397-1404
Published in print January 2006 | ISSN: 1054-3139
Published online January 2006 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2006.04.024
Using multi-angle scattered sound to size fish swimbladders

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Common current practice in fisheries acoustics is to use sound that has been backscattered at 180° in order to infer parameters of individual or aggregations of animals. This article proposes that there is interesting information that can be obtained by processing scatter from other observation angles. Using a simple one-dimensional model of scatter from a fish swimbladder, an expression is derived that predicts the location of the nulls of the scattered sound as a function of transmit angle, observation angle, and tilt. The model was used retrospectively to compute the size of a swimbladder from an existing data set (that of Foote, K. G. 1985. Rather-high-frequency sound scattering by swimbladdered fish. Journal of the Acoustical Society of America, 78: 688–700), with good agreement. In order to pursue the development of a pragmatic collection system, a method is suggested that uses a single transmitter with multiple receivers. The locations of the receivers can be determined using a design methodology that considers bandwidth, centre frequency, and the size of the intended object. The method ensures that a spatially unaliased backscattered waveform can be measured over a specified sampling interval. The technique is illustrated with a practical example that uses a small number of receivers, placed in the backscattered hemisphere.

Keywords: acoustic diffraction; multi-angle sound; swimbladder estimation

Journal Article.  4611 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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