The document discusses principles and techniques for analyzing acoustic data to assess fish stocks, including echo integration, density estimation, and mapping fish distribution. Key points covered include defining analysis cells and resolution, counting and tracing echoes, estimating sampled volume and density, and producing horizontal and vertical maps of survey results. The software described allows integrating echo returns to estimate fish biomass from hydroacoustic surveys.

1. Principles of Fisheries Acoustics
Data Analysis
Hydroacoustics 103
By
BioSonics, Inc.
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2. Using BioSonics Visual Analyzer™
Acoustic Data Analysis Software
For Fish Stock Assessment
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3. Data Analysis Module
Point-Source Targets:
Echo Recognition and Counting
Trace Formation
Volumetric Analysis:
Bathymetry (depth)
Echo Integration (fish)
VBT (Sea Floor Classification)
EcoSAV (Submerged Vegetation)
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4. Multiple Targets in Fish Schools
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5. Counting When Single Targets Are Resolved
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6. Range and Angular Resolution
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7. Resolving Fish Echoes
t2 – t1 > pulse duration
(2 R2 / c) - (2 R1 / c) >
R2 –R1 > (c / 2) for no
overlap
____________________
c = 1500 m/second
= 1.5 m/msec
c/2 = 3/4 m/msec
t0 t1 = (2 R 1 / c) t2 = (2 R 2 / c)
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8. Dead Zone Near Bottom
Fish can not be detected
in “dead zone” near
boundaries (here bottom).
“Dead zone” near the
bottom is defined by
beam angle, range, and
pulse duration.
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9. Visual Resolution
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10. Digital Resolution
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11. Single and Overlapping Echoes
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12. Pulse Duration Criteria
V
-6 dB level or 0.5 amplitude
-12 dB level or 0.25 amplitude
Threshold
-18 dB level or 0.125 amplitude
Time
Duration of echo should be approximately equal to duration of transmitted pulse.
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13. Single Target Criteria: Echo Correlation
Comparing of shape of echo envelope with transmitted pulse
n
fish echo transmit replica
i 1
Correlatio n
n n
2 2
fish echo transmit replica
i 1 i 1
Where: n = the number of samples in an ideal pulse, i = sample index
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14. Counting Methods
• Require Single Echo Recognition
• Echoes Over Threshold are Counted
• Echoes May be Assembled into Fish Traces
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15. Abundance Estimation
• Count Echoes
• Estimate Sampled Volume
• Calculate Density
• Extrapolate over Sample Area to Estimate
Abundance
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16. Density Estimation from Trace Counts
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17. Density Estimation from Echo Counts
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18. Sample Volume Estimate
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19. Overlap Biases
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20. Echo Integration
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21. Echo Integration
• Technique used for echo signal processing of multiple
objects.
• Summing echo intensity (energy) from multiple objects in
a sampling volume or sampling area.
• Various processing algorithms (averaging, filtering, etc.)
• Echo integration can be used for:
• Assessment of density (biomass) of fish, plankton, particles,
etc.
• Bottom classification
• Aquatic vegetation assessment
• EI survey data can be used for mapping if acquired with
GPS information.
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22. Echo Integration Principle
•I = N * bs
•I V2
•Density = V2 * A
•A is the Echo Integrator Scaling Factor
•In digital form V2 is the sum of squared digital sample
count values
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23. Digital Signal Integration
•Only samples greater than threshold are processed.
•Samples less than threshold level are rejected.
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24. Scaling Factor of Echo Integrator
Fish Parameter Instrument parameters
Where sonar system parameters are defined as:
Source Level => Transmitted Power ( Pa at 1 m) SL = 10 log p02
Receiver Sensitivity => System Gain (V/ Pa) G=10 log g2
Beam pattern factor: b2( )
Sound velocity: c (m / s)
Pulse duration: (ms)
2003-2009 Copyright BioSonics, Inc. All Rights Reserved

25. Echo Integration High Densities
• Fish densities in lakes and oceans are on the order of 10-4 to 10-2 fish/m3 (scattered fish,
median densities).
• Fish densities in schools and in aquaculture pens (nets) are much higher: from 1 to 100
fish/m3, or up to 20 kg/m3.
• Echo Integration is linear for low and medium densities, then begins to saturate.
• The classic echo integration theory, based on the single scattering model, can not be
applied for estimation of fish in high density aggregations due to attenuation of echo
signal by densely distributed scatterers.
Echo Integrator Saturation
3
Echo Integrator Output
2.5
2
1.5
1
0.5
0
1
18
35
52
69
86
103
120
137
154
171
188
205
222
239
256
273
290
307
324
341
Fish Density
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26. Models of Echo Integration
L o w d en sities H ig h d en sities V ery H ig h d en sities
S in g le S catterin g S in g le S catterin g w ith M u ltip le S catterin g
A tten u atio n
E n ergy
tran sp o rt
ran g e
F o r v ery h ig h d en sity th e en v iron m en t co m es to b e
n o n ho m o g en o u s:
m ix tu re of w ater an d fish b od ies
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27. Example of Echo Integration using Visual Analyzer
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2003-2009 the bottom exclusion algorithm

28. Step 2: Program Echo Recognition
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29. Step 3: Define Analysis Cells and Resolution
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30. VERTICAL INTEGRATION RESULTS
STRATA TOP BOTTOM Sv (dB) Applied Sigma FPCM
------ ------ ------ ------------- ------------- -------------
1 1 4 -8.30E+01 1.00E-03 5.03E-06
2 4 6.9 -6.07E+01 1.00E-03 8.59E-04
3 6.9 9.9 -6.64E+01 1.00E-03 2.31E-04
4 9.9 12.9 -5.45E+01 1.00E-03 3.58E-03
5 12.9 15.9 -4.86E+01 1.00E-03 1.39E-02
HORIZONTAL INTEGRATION RESULTS
RPT T IM E A N D D A T E D epth Latitud e Long itu de S v (dB ) S ig m a FPUA
1 10/0 1/96 21:27:00 7.4 41ø 30 .34 00' N 119ø 3 .64 00' W -5.50 E + 01 1.00 E -03 1.15 E -02
2 10/0 1/96 21:27:49 12.8 41ø 30 .32 00' N 119ø 3 .68 00' W -5.66 E + 01 1.00 E -03 6.91 E -03
3 10/0 1/96 21:28:35 13.5 41ø 30 .30 00' N 119ø 3 .72 00' W -5.66 E + 01 1.00 E -03 8.65 E -03
4 10/0 1/96 21:29:23 13.2 41ø 30 .32 00' N 119ø 3 .75 00' W -5.28 E + 01 1.00 E -03 9.38 E -03
5 10/0 1/96 21:30:13 10.5 41ø 30 .28 00' N 119ø 3 .82 00' W -5.24 E + 01 1.00 E -03 4.94 E -03
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31. V O L U M E B A C K S C A T T E R IN G S T R E N G T H (d B )
REPORT 1 REPORT 2 REPORT 3 REPORT 4 REPORT 5
STRATA 1 -8 .8 4 E + 0 1 -9 .0 1 E + 0 1 -7 .8 8 E + 0 1 -8 .4 9 E + 0 1 -8 .2 0 E + 0 1
STRATA 2 -5 .3 7 E + 0 1 -8 .7 1 E + 0 1 -9 .9 1 E + 0 1 -1 .0 7 E + 0 2 -7 .9 7 E + 0 1
STRATA 3 -5 .9 8 E + 0 1 -7 .2 4 E + 0 1 -7 .4 2 E + 0 1 -9 .1 5 E + 0 1 -8 .4 0 E + 0 1
STRATA 4 -4 .9 8 E + 0 1 -5 .7 4 E + 0 1 -5 .8 8 E + 0 1 -5 .8 5 E + 0 1 -5 .5 4 E + 0 1
STRATA 5 0 .0 0 E + 0 0 -5 .0 5 E + 0 1 -5 .0 2 E + 0 1 -4 .6 0 E + 0 1 -4 .5 8 E + 0 1
A B S O L U T E D E N S IT Y D IS T R IB U T IO N M A T R IX (IN N U M B E R P E R C U B IC M E T E R )
REPORT 1 REPORT 2 REPORT 3 REPORT 4 REPORT 5
STRATA 1 1 .4 6 E -0 6 9 .7 6 E -0 7 1 .3 1 E -0 5 3 .2 3 E -0 6 6 .3 7 E -0 6
STRATA 2 4 .2 8 E -0 3 1 .9 6 E -0 6 1 .2 4 E -0 7 2 .0 9 E -0 8 1 .0 8 E -0 5
STRATA 3 1 .0 6 E -0 3 5 .8 2 E -0 5 3 .7 9 E -0 5 7 .0 8 E -0 7 4 .0 3 E -0 6
STRATA 4 1 .0 5 E -0 2 1 .8 4 E -0 3 1 .3 3 E -0 3 1 .4 0 E -0 3 2 .8 8 E -0 3
STRATA 5 0 .0 0 E + 0 0 9 .0 1 E -0 3 9 .5 4 E -0 3 2 .4 9 E -0 2 2 .6 1 E -0 2
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32. P E R C E N T IN T E G R A T E D M A T R IX
REPORT 1 REPORT 2 REPORT 3 REPORT 4 REPORT 5
STRATA 1 95.6 47 94.5 74 89.4 06 93.2 82 95.0 9
STRATA 2 71.5 98 95.1 5 89.9 51 93.8 5 91.1 89
STRATA 3 32.4 26 94.5 74 89.4 06 93.2 82 67.3 54
STRATA 4 4.32 81.3 76 89.9 51 93.8 5 45.3 28
STRATA 5 0 8.51 5 17.4 8 7.36 9 1.28 9
Percentage of integrated matrix is needed for estimation of sampling
volume and biomass. Near the bottom sampling volume is smaller due
to appearance of a bottom signal and this volume is not taken into
consideration when estimating biomass:
BIOMASS = FISH DENSITY * VOLUME
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33. Horizontal map of survey
Survey Output Reports were imported to GIS and data were interpolated
Fish Density per Unit Surface (1/m2) or (kg/m2)
Absolute Density = A (Relative Density) A: Scaling factor
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Biomass = (Average Absolute Density) (Survey

34. Vertical cross-section of the transect
Fish Density per Unit Volume (1/m3) or (kg/m3)
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35. Visual Bottom Typer
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36. EcoSAV
Software for Measuring
Submerged Rooted Vegetation
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