M. Moszynski et Jb. Hedgepeth, Using single-beam side-lobe observations of fish echoes for fish target strength and abundance estimation in shallow water, AQU LIV RES, 13(5), 2000, pp. 379-383
Acoustic surveys for determining fish abundance in shallow water present ma
ny challenges. One constraint to down-looking (or vertical) surveys is that
the sampling volume is Limited due to the short range and typically narrow
beams of acoustic transducers. By utilizing more of the acoustic beam, int
o the side-lobes for example, the sampling volume may be increased. Althoug
h the echo energy contribution from the side-lobes is usually small, these
echoes may influence target strength estimation and echo counting, and by e
xtension affect abundance estimation either directly or indirectly. With th
e advent of wide dynamic range echosounders, it is possible to assess both
small and large acoustic-size targets. In this case, it is possible to coll
ect signals from large targets in the beam side-lobes, and therefore an alg
orithm to use side-lobe data is proposed. The smoothed expectation Maximiza
tion method (EMS) is used to estimate densities and target strength of fish
from only main-lobe and main-lobe with side-lobe observations in simulatio
n, and suggestions are made for real data from surveys. (C) 2000 Ifremer/CN
RS/INRA/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS.