caa a22 4500 397550375 CHVBK 20180308164748.0 cr unu---uuuuu 161202e199604 xx s 000 0 eng 10.1006/jmsc.1996.0057 doi (NATIONALLICENCE)oxford-10.1006/jmsc.1996.0057 Kloser Rudy J. CSIRO Marine Laboratories, PO Box 1538, Hobart, Tasmania 7001, Australia Improved precision of acoustic surveys of benthopelagic fish by means of a deep-towed transducer [Elektronische Daten] [Rudy J. Kloser] Acoustic measurements of deepwater fish from a deep-towed transducer deployed at depths from 500 to 650 m over a seamount (rising from 1000 to 600 m depth) are compared with those from a vessel-mounted transducer. Algorithms were developed to correct for noise and to analyse signals near the bottom. The analysis showed that the vessel-mounted transducer can significantly underestimate the volume reverberation of deepwater fish by an average factor of 1.86, equating to 2.7 dB. This bias was largely attributed to beam thresholding and calibration, acoustic attenuation from near-surface bubbles, ship motion, and uncertainties in the sound absorption constant. On the steepest slope of the seamount the near-bottom shadow zone was reduced by 50% and the extrapolated biomass in this zone reduced by 47% using the deep-towed transducer. These results confirm that a deep-towed transducer will improve absolute abundance measurements of deepwater resources. © 1996 International Council for the Exploration of the Sea Regular Articles nationallicence acoustic surveys nationallicence orange roughy nationallicence towed body nationallicence ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 407-413 1054-3139 53:2<407 1996 53 icesjms https://doi.org/10.1006/jmsc.1996.0057 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1006/jmsc.1996.0057 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Kloser Rudy J. CSIRO Marine Laboratories, PO Box 1538, Hobart, Tasmania 7001, Australia NATIONALLICENCE 773 0- ICES Journal of Marine Science Oxford University Press 53/2(1996-04), 407-413 1054-3139 53:2<407 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