Monitoring fish migration in Rivers

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Monitoring fish migration in Rivers

• Helge Balk
• Department of Physics. University of Oslo.

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River Tana
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River Tana
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Tornio (Se/Fi)
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River Reisa (north Norw.)
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River Fischa in Austria
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Echosounder in the river
Amplitude Detector
1 size correction
Phase detector
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What we can do to increase the detection
probability
Estimate the DPF Reduce the variation in the DPF
Site selection Bottom modification Surface
modification Guide fish Opening angle Sound
frequency
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If we detect a fish, What does it mean?
Echo sounder
Fish detection software
?
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Interpretation DPF, noise and time expansion
Echo sounder
Fish detector
Interpreter
Meaningful statistics
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
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Interpretation Area expansion
!
Echo sounder
Fish detector
Interpreter
Meaningful statistics!
Where did the fish pass? Index or total run?
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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?
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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