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300-kHZ 多波束及 120-kHZ 分割波束漁探機對於大西洋鱈之聲學反射及魚群密度量測

981 專題討論. Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders. 300-kHZ 多波束及 120-kHZ 分割波束漁探機對於大西洋鱈之聲學反射及魚群密度量測 Gurshin, C. W. D., Jech, J. M., Howell, W. H., Weber, T. C., and Mayer, L. A. 2009.

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300-kHZ 多波束及 120-kHZ 分割波束漁探機對於大西洋鱈之聲學反射及魚群密度量測

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  1. 981專題討論 Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders 300-kHZ多波束及120-kHZ分割波束漁探機對於大西洋鱈之聲學反射及魚群密度量測 Gurshin, C. W. D., Jech, J. M., Howell, W. H., Weber, T. C., and Mayer, L. A. 2009. ICES Journal of Marine Science, 66: 1303–1309. Speaker: 黃星翰

  2. Fishery Echosounder • TS：target-strength （dB） • sA：nautical area scattering coefficient （m2／ m2） • Sv：volume backscattering strength （dB）

  3. Introduction • Acoustic vs. trawl survey • Echosounder series • Multibeam echosounder • Materials and methods • Sample processing • Experiment • Data analysis • Results • EK60 vs. EM3002 • Discussion • Results

  4. Introduction

  5. Fishery-acoustic vs. Traditional trawl survey • Fish density • Biomass • Spatial distribution • Behaviour

  6. Multibeam echosounders

  7. Objective • Fewer application for demersal species • Not widely developed in the United States • Comparing split-beam and multibeam

  8. Materials and methods

  9. Atlantic cod http://www.fishbase.org/Summary/SpeciesSummary.php?id=69

  10. Sample processing

  11. Apparatus Simrad EK60 120kHz splitbeam echosounder Kongsberg EM3002 300kHz multibeam echosounder

  12. Experimental setup

  13. Data analysis Post-processing software：Echoview and Matlab Statistical analysing software：SAS and R AWC＝EL－SL－10 log10(ΩTXΩRX) ＋2αR＋30 log10R＋Ｃ Sv＝AWC－( X－20)10 log10(R) －10 log10(cτ/2) EL：echo level SL：source level α：attenuation coefficient ΩTX ：transmitting beam width ΩRX ：receiving beam width R ：range from the transducer C ：calibration gain Sv：volume-backscattering strength （dB） X ：collection of Awc c ：sound speed （ms－1） τ ：pulse duration （s）

  14. Svfor the EM3002 64dB dynamic range

  15. Cod ：128 Cod ：116 Cod ：66 Threshold ： －36dB Cod ：23

  16. Svfor the EK60 Threshold ： －30dB Cod ：128 Cod ：66

  17. Results

  18. 14dB

  19. TSa ＝20 log (LT) －65 (Rose and Porter, 1996) at 120kHz, where LT is the total length (cm). bSv＝TS＋10 log (N/V) , where N is the number of cod in the sampled volume V.

  20. 6 dB 7 dB

  21. Discussion

  22. Sv Random and homogeneous distribution of target Constant fish orientations (assuming linearity in echo-integration)

  23. Sensitivity high low

  24. Improvement • Limitation • 64 dB dynamic range • Split-beams detection in the athwartships direction only • Nearfield range of ~7m • Simrad ME70 • Adjustable beam width（2.2 - 20°） • Split-beam operating at multiple • frequencies • Calibration of all beams • Single-target detections • TS estimations • Quantification of the effect of different incidence angle and overlapping beams on volume-backscatter measurements

  25. Thanks for your attention

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