measurements of acoustic backscatter and density of captive atlantic cod with synchronized 300-khz...
TRANSCRIPT
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.
981專題討論
Speaker : 黃星翰
Fishery Echosounder
TS : target-strength ( dB)
sA : nautical area scattering coefficient ( m2 / m2)
Sv : volume backscattering strength ( dB)
IntroductionIntroductionAcoustic vs. trawl surveyAcoustic vs. trawl surveyEchosounder seriesEchosounder seriesMultibeam echosounderMultibeam echosounder
Materials and methodsMaterials and methodsSample processingSample processingExperimentExperimentData analysisData analysis
ResultsResultsEK60 vs. EM3002EK60 vs. EM3002
DiscussionDiscussionResultsResults
Introduction
Fishery-acousticFishery-acoustic vs. Traditional trawl survey vs. Traditional trawl survey
•Fish density
•Biomass
•Spatial distribution
•Behaviour
Multibeam echosoundersMultibeam echosounders
ObjectiveObjective
Fewer application for demersal species
Not widely developed in the United States
Comparing split-beam and multibeam
Materials and methods
Atlantic codAtlantic cod
http://www.fishbase.org/Summary/SpeciesSummary.php?id=69
Sample processingSample processing
ApparatusApparatusSimrad EK60 120kHz splitbeam echosounder
Kongsberg EM3002 300kHz multibeam echosounder
7° Beam width 130°
23 mm copper Standar sphere 38.1 mm tungsten-carbid
8 - 10 m Calibrate depth 8 - 10 m
Experimental setup
Data analysisData analysis
Post-processing software : Echoview and Matlab
Statistical analysing software : SAS and R
AWC = EL - SL - 10 log10(ΩTXΩRX) + 2αR + 30 log10R+CSv = AWC - ( X - 20)10 log10(R) - 10 log10(cτ/2)
EL : echo levelSL : source levelα : attenuation coefficientΩTX : transmitting beam width
ΩRX : receiving beam widthR : range from the transducerC : calibration gain
Sv : volume-backscattering strength ( dB)X : collection of Awc
c : sound speed ( ms - 1)τ : pulse duration ( s)
Sv for the EM3002
64dB dynamic range
Threshold :- 36dB
Cod : 128
Cod : 23Cod : 66
Cod : 116
Sv for the EK60Threshold :- 30dB
Cod : 128
Cod : 66
Results
14dB
Date 25 June 26 June 27 June 27 June 28 June
Depth ( m) 6.5 7.2 8.0 11.0 8.8
LT ( cm) 80.7 81.1 82.1 82.1 82.9
n 128 116 66 66 23
Percentage 100 91 52 52 18
Total pings 1500 7140 1680 1800 5940
300kHz EM3002Sv ( dB ;95 % CI)
- 29.8(- 30.3, -
29.3)
- 31.7(- 31.9, -
31.5)
- 28.4(- 28.7, -
28.2)
- 29.1(- 29.4, - 28.
8)
- 39.7(- 40.3, - 39.
1)
300kHz EM3002Percentage
100 65 138 117 10
120kHz EK60Sv ( dB ;95 % CI)
- 29.4(- 30.0, -
28.8)
- 26.5(- 26.9, -
26.2)
- 23.6(- 24.2, -
23.1)
- 26.4(- 26.9, - 25.
8)
- 38.8(- 40.0, - 37.
8)
120kHz EK60Percentage
100 195 380 200 11
TSa - 26.9 - 26.8 - 26.7 - 26.7 - 26.6
Expectedb Sv at 120kHz
- 25.7 - 26.1 - 28.4 - 28.4 - 32.9
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.
6 dB7 dB
Discussion
SSvv
1. Random and homogeneous distribution of target
2. Constant fish orientations(assuming linearity in echo-
integration)
SensitivitySensitivity
high low
ImprovementImprovementLimitation 64 dB dynamic range Split-beams detection in the athwartships direction only Nearfield range of ~7m
Simrad ME70Adjustable 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
Thanks for your attention