New Zealand Journal of Marine and Freshwater Research abstracts

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Minimising errors in estimating fish population and biomass densities using the 'acoustic volume backscattering strength' method

M. A. DO

Fisheries Research Centre Ministry of Agriculture and Fisheries P. O. Box 297 Wellington, New Zealand

Abstract The basic acoustical methods for estimating the volume backscattering strength and the absolute biomass density are commonly known. However, the detailed techniques for minimising errors in fitting the calibrated parameters of an echo sounding system in these computations are still not adequately examined and discussed. This paper describes and discusses the following computing techniques involved in the absolute biomass estimation: (i) the fitting of the calibrated time varied gain (TVG) curve, the selection of its operating interval, and the correction of its response; (ii) the compensation for the limitation of the signal bandwidth; (iii) the computation of the equivalent beam width of a transducer using its calibrated beam patterns; and (iv) the accuracy in the conversion from the volume backscattering to the absolute fish density using individual fish target strength measurements.

Keywords mean volume backscattering strength; fish population density; fish biomass density; TVG; bandwidth; equivalent beam width; calibration

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 99-108 OO28-8330/87/2101-0O99$2.50/0 © Crown copyright 1987 Received 30 January 1986; accepted 23 June 1986

PDF file of entire paper: medium quality (836K); (scanned from paper original: notes about this process)

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