Effects of fish school structures on acoustic scat

Authors: Alvarez A Ye Z

Publish Date: 1999/06/01

Volume: 56, Issue: 3, Pages: 361-369

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Abstract

The effects of the structure of a fish school on the backscattering signal are reported A numerical model has been employed to calculate the effective scattering function of the small fish schools incorporating all orders of multiple scattering between fish It is shown that when the fish school has certain order regular scattering patterns may appear resulting from the interference rather than the multiple scattering The interference peaks are due to inphase scattering and can be explained by the Bragg reflection mechanism Such regular interference patterns are gradually degraded as the random deviation in each individual fish location from its mean position increases When the random deviation is strong enough the widely used random phase approximation RPA method is shown to be valid Furthermore a validity criterion has been found for the RPA approach that is kσ≥1 with k being the wavenumber and σ the standard deviation of the fish position distribution

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