Issue |
Aquat. Living Resour.
Volume 14, Number 4, July 2001
|
|
---|---|---|
Page(s) | 211 - 222 | |
DOI | https://doi.org/10.1016/S0990-7440(01)01121-4 | |
Published online | 15 July 2001 |
Correction on school geometry and density: approach based on acoustic image simulation
TMSI/TP, Ifremer centre de Brest, BP 70, 29280 Plouzané cedex, France
Received:
12
July
2000
Accepted:
26
March
2001
Models of simulated schools have been used to determine the intrinsic variability in echotraces due to beam pattern effect. This work concerns only morphometric and energetic parameters that can be extracted from echotraces. It appears that dST, the difference between school density and processing threshold is a key parameter, which directly influences the concerned detection angles. Relations, taking into account dST but also, Nbi, the relative school length image compared to the beam width, have been settled for the calculation of length and density corrections. In most cases, corrected values are obtained with errors less than respectively 5% for length and 0.5 dB for density (reverberation index), provided that the Nbi value is 1.5 or more. When Nbi is less than 1, it seems impossible to bring some pertinent corrections. The school energy does not need any correction. It is recommended to use threshold values not too low, to avoid detection through the side lobes. However this setting must be determined in order to obtain dST values greater than 10 dB. Thresholds between –60 and –65 dB seem adequate, at least for schools volume backscattering strength (VBS, Sv) values commonly encountered in the Bay of Biscay.
Key words: acoustic / fish detection / fish schools
© Elsevier, IRD, Inra, Ifremer, Cemagref, CNRS, 2001
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.