• Title/Summary/Keyword: acoustic target strength %28TS%29

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Acoustic Target Strength of the Pelagic Fish in the Southern Waters of Korea I. In situ Measurement of Target Strength of Anchovy (Engraulis japonica) (한국 남해안 부어류의 음향반사강도에 관한 연구 I. 멸치 (Engraulis japonica)의 in situ 반사강도 측정)

  • YOON Gab Dong;KIM Zang Geun;CHOI Young Min
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.29 no.1
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    • pp.107-114
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    • 1996
  • The in situ target strength for the anchovy (Engraulis japonica) were measured by the split beam echo sounder system at 38 kHz. This study allowed us to detect the single echos from anchovy shoals which were dispersed during trawling operation in day time. The results of our study were as fellows: We found that the anchouy occupied about $95\%$ of the total catch from the detected shoals from which target strength data were collected. Length distribution of anchovy showed a mode and ranged from 13.6 to 15.4cm with a mean of 14.4cm and a standard deviation of 0.45cm, and weight distribution showed a mode and ranged from 16 to 28 g witha mean of 21.9 g and a standard deviation of 2.7 g. The target strength distribution of anchovy ranged from -40.7 dB to -69.2 dB in the water layer of ,$10\~30\;m$ -42.19 to -67.7 dB in the $30\~50\;m$ and -42.2 to -67.7 dB in $10\~50\;m$, showing 2 modes in each layer, respectively. Overall mean target strengths were -49.7 dB/fish and -33.1 dB/kg, averaged by area backscattering cross section $(\sigma)$, and the confidence interval for target strength was less than 1 dB. With the mean total length and the mean target strength, we drived the target strength-length relationship as $TS(\sigma)=20\;Log\;L-72.9$.

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Acoustic Scattering Characteristis of the Individual Fish (어체의 초음파 산란특성에 관한 연구)

  • 신형일
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.27 no.1
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    • pp.21-30
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    • 1991
  • The estimation of the fish biomass density or the size of fish by means of the acoustic equipment is an important part in the quantitative assessment of fisheries resources. The precision of such estimates depend upon the target strength of fish and the accuracy to which the acoustic equipment has been calibrated. This paper examine the accuracy of the digital measurement system which is manufactured by way of trial in order to masure the target strength of fish, and calibrations of that system carry out with an ogive and a ellipsoid made of the aluminum and the epoxy, respectively. Furthermore, measurements of target strength for eight species of fish are made at 25, 50, 100 kHz. The accuracy of the digital measurement system is compared the theory with measurements on ogive and ellipsoid, and the agreement is reasonable. Result of establishments on the target strength to fish length and to fish weight regression obtained from the measurements are available to provide the methods of design for use in interpreting acoustic measurements of fish abundance on the experimented eight species.

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