Acoustic density estimation of dense fish shoals

Area of Science:

• Marine acoustics
• Fisheries science
• Bioacoustics

Background:

• Traditional fish density estimation methods like echo-counting and echo-integration are ineffective for dense fish shoals.
• Acoustic wave scattering offers a potential noninvasive alternative for such challenging scenarios.

Purpose of the Study:

• To investigate the application of multiple acoustic wave scattering for noninvasive fish density estimation in dense shoals.
• To quantitatively interpret the coherent backscattering effect in fish shoals using multi-beam sonar.

Main Methods:

• Conducting acoustic experiments in open sea cages using a multi-beam sonar system.
• Observing and analyzing multiple scattering of sound within fish shoals.
• Performing volumetric scans to isolate individual fish and estimate their target strength.

Main Results:

• Multiple scattering of sound, including the coherent backscattering effect, was observed and quantitatively interpreted in fish shoals.
• Individual fish target strength estimations were achieved through volumetric scanning.
• A combined approach of scattering analysis and target strength estimation enabled fish density determination.

Conclusions:

• Multiple acoustic wave scattering is a viable noninvasive method for estimating fish density in dense shoals.
• The coherent backscattering effect provides valuable information for acoustic density estimation.
• This combined acoustic methodology overcomes limitations of traditional techniques in challenging dense shoal environments.