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Monitoring fish migration in Rivers
Helge Balk
Department of Physics. University of Oslo.
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River Tana River Tana
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River TanaRiver Tana
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Tornio (Se/Fi)Tornio (Se/Fi)
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River Reisa River Reisa (north Norw.)(north Norw.)
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River Fischa in River Fischa in AustriaAustria
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Echosounder in the river Echosounder in the river
Phase detector
AmplitudeDetector
4-ChTVG
1 size correction
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What we can do to increase the What we can do to increase the detection probability detection probability
Site selection
Bottom modification
Surface modification
Guide fish
Opening angle
Sound frequency
Estimate the DPF
Reduce the variation in the DPF
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If we detect a fish, What does it If we detect a fish, What does it mean?mean?
Echo sounder
?
Fish detection software
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Interpretation: DPF, noise and time Interpretation: DPF, noise and time expansionexpansion
Measure noise level as a function of time and range over years
Apply noise level as an overall fish size threshold
Use noise level to correct the number of fish within each size group
Apply time expansion to find the total fish abundance estimate
Noise level
Threshold
Intensity
1 2 3 4 5 6 7 8 9 10 Time
High noiselevel
Halt inrecording
High noiselevel
Echo sounder
Fish detector Meaningful
statistics
Interpreter
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Interpretation: Interpretation: Area expansionArea expansion
Echo sounder Meaningful
statistics!
Covered areaUncovered area
1
0
2
3
2
1
What did we cover?
Where did the fish pass?
Index or total run?
Fish detector
Interpreter
!
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Can we estimate TS in a river? Can we estimate TS in a river?
Spherical or cylindrical spreading? Corrupted vertical angular measurements? Additive noise? Can we compensate for swimming motion?
Can we compensate for fish aspect?
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Can we estimate TS in a river?Can we estimate TS in a river?
Alternative methods to establish the size?
Beam intensity mapping?
Apply reference targets?
Multiple narrow beams?
Multiple frequencies?
Aspect detection and correction?
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