海洋音響学会誌
Online ISSN : 1881-6819
Print ISSN : 0916-5835
ISSN-L : 0916-5835
論文
Shape and Target Strength of Vesicles of two Sargassum Species Common to the Coastal Waters of Japan
Kenji MINAMIAkira HAMANOTakeshi NAKAMURAYoshimi TAKAOHiroki YASUMAKazushi MIYASHITA
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2010 年 37 巻 3 号 p. 147-155

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The size of vesicles and amount of gas they contain is a major factor in the acoustic scattering of Sargassum plants. Here we investigate the morphological character of the vesicles and gas, and their theoretical and experimental target strength (TS) for two Sargassum species, Sargassum macrocarpum and S. siliquastrum. Both species are abundant in the coastal waters of Japan. A total of 593 vesicles were measured using a soft X-ray system, and their gas shapes were applied to two theoretical TS models (non-resonance and resonance). Experimental TS were obtained at 70 and 200 kHz using quantitative echo sounders in a freshwater tank. Gas fields were found in 418 vesicles, and the gas radius and external size of the vesicles were linearly related in both species. The theoretical TS of the non-resonance model was similar to the experimental TS of large vesicles (≥4.1 mm at 70 kHz, ≥2.8 mm at 200 kHz), whereas the theoretical TS of the resonance model was similar to the experimental TS of small vesicles (≤3.1 mm at 70 kHz, ≤1.9 mm at 200 kHz). Finally, we estimated TS-size equations according to the gas-size relationships and compared the results.

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© 2010 Marine Acoustics Society of Japan
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