Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms
Stanton, Timothy K.
Wiebe, Peter H.
Martin, Linda V.
Eastwood, Robert L.
MetadataShow full item record
The acoustic scattering properties of live individual zooplankton from several gross anatomical groups have been investigated. The groups involve (1) euphausiids (Meganyctiphanes norvegica) whose bodies behave acoustically as a fluid material, (2) gastropods (Limacina retroversa) whose bodies include a hard elastic shell, and (3) siphonophores (Agalma okeni or elegans and Nanomia cara) whose bodies contain a gas inclusion (pneumatophore). The animals were collected from ocean waters off New England (Slope Water, Georges Bank, and the Gulf of Maine). The scattering properties were measured over parts or all of the frequency range 50 kHz to 1 MHz in a laboratory-style pulse-echo setup in a large tank at sea using live fresh specimens. Individual echoes as well as averages and ping-to-ping fluctuations of repeated echoes were studied. The material type of each group is shown to strongly affect both the overall echo level and pattern of the target strength versus frequency plots. In this first article of a two-part series, the dominant scattering mechanisms of the three animal types are determined principally by examining the structure of both the frequency spectra of individual broadband echoes and the compressed pulse (time series) output. Other information is also used involving the effect on overall levels due to (1) animal orientation and (2) tissue in animals having a gas inclusion (siphonophores). The results of this first paper show that (1) the euphausiids behave as weakly scattering fluid bodies and there are major contributions from at least two parts of the body to the echo (the number of contributions depends upon angle of orientation and shape), (2) the gastropods produce echoes from the front interface and possibly from a slow-traveling circumferential (Lamb) wave, and (3) the gas inclusion of the siphonophore dominates the echoes, but the tissue plays a role in the scattering and is especially important when analyzing echoes from individual animals on a ping-by-ping basis. The results of this paper serve as the basis for the development of acoustic scattering models in the companion paper [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998)].
Author Posting. © Acoustical Society of America, 1998. 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 103 (1998): 225-235, doi:10.1121/1.421469.
Suggested CitationArticle: Stanton, Timothy K., Chu, Dezhang, Wiebe, Peter H., Martin, Linda V., Eastwood, Robert L., "Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms", Journal of the Acoustical Society of America 103 (1998): 225-235, DOI:10.1121/1.421469, https://hdl.handle.net/1912/2514
Showing items related by title, author, creator and subject.
Differences between sound scattering by weakly scattering spheres and finite-length cylinders with applications to sound scattering by zooplankton Stanton, Timothy K.; Wiebe, Peter H.; Chu, Dezhang (Acoustical Society of America, 1998-01)A modeling study was conducted to determine the conditions under which fluidlike zooplankton of the same volume but different shapes (spherical/cylindrical) have similar or dramatically different scattering properties. ...
Broadband and statistical characterization of echoes from random scatterers : application to acoustic scattering by marine organisms Lee, Wu-Jung (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-02)The interpretation of echoes collected by active remote-sensing systems, such as sonar and radar, is often ambiguous due to the complexities in the scattering processes involving the scatterers, the environment, and the ...
Stanton, Timothy K.; Chu, Dezhang; Wiebe, Peter H. (Acoustical Society of America, 1998-01)Mathematical scattering models are derived and compared with data from zooplankton from several gross anatomical groups—fluidlike, elastic shelled, and gas bearing. The models are based upon the acoustically inferred ...