caa a22 4500 397551614 CHVBK 20180308164751.0 cr unu---uuuuu 161202e199604 xx s 000 0 eng 10.1006/jmsc.1996.0048 doi (NATIONALLICENCE)oxford-10.1006/jmsc.1996.0048 Dual-beam echo integration method for precise acoustic surveys [Elektronische Daten] [Yoshimi Takao, Masahiko Furusawa] The echo integration method has been widely and effectively used for acoustic surveys of fisheries resources. In recent quantitative echo-sounders the dual-beam or split-beam method has been adopted, which improves the accuracy of in situ target strength (TS) measurement. The dual-beam method utilises a coaxial narrow and wide-beam pair. In ordinary dual-beam systems, echo integration is performed only for the narrow-beam signal, not for the wide-beam signal. If echo integration is also performed for the wide-beam signal, more information and better accuracy and precision of the acoustic survey of fish abundance can be gained. Comparing the integrator outputs of both beams, an index of avoidance behaviour of fish towards the surveying vessel can be compiled and unreliable measurements caused by, for example, noise contamination and failure in bottom detection can be found. Wide-beam integration is of better use when distributions of fish are shallow and sparse, because the sampling volume is greater. Furthermore, the error caused by transducer motion in bad weather conditions is smaller for the wide beam. By combining both beam echoes, the volume backscattering strength within individual fish schools can be measured precisely. The method is discussed theoretically. Experimental investigations were carried out on walleye pollock (Theragra chalcogramma (Pallas)), in the Bering Sea by our quantitative echo-sounding system, which provides independent echo integration results for both narrow and wide beams. © 1996 International Council for the Exploration of the Sea Regular Articles nationallicence acoustic survey nationallicence avoidance behaviour nationallicence dual-beam method nationallicence echo integration nationallicence Takao Yoshimi National Research Institute of Fisheries Engineering, Ebidai Hasaki, Kashima Ibaraki, 314-04, Japan aut Furusawa Masahiko National Research Institute of Fisheries Engineering, Ebidai Hasaki, Kashima Ibaraki, 314-04, Japan aut ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 351-358 1054-3139 53:2<351 1996 53 icesjms https://doi.org/10.1006/jmsc.1996.0048 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1006/jmsc.1996.0048 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Takao Yoshimi National Research Institute of Fisheries Engineering, Ebidai Hasaki, Kashima Ibaraki, 314-04, Japan aut NATIONALLICENCE 700 1- Furusawa Masahiko National Research Institute of Fisheries Engineering, Ebidai Hasaki, Kashima Ibaraki, 314-04, Japan aut NATIONALLICENCE 773 0- ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 351-358 1054-3139 53:2<351 1996 53 icesjms Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford