Journal Article

A comparative acoustic-abundance estimation of pelagic redfish (<i>Sebastes mentella</i>) from hull-mounted and deep-towed acoustic systems

John Dalen, Kjell Nedreaas and Ronald Pedersen

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 60, issue 3, pages 472-479
Published in print January 2003 | ISSN: 1054-3139
Published online January 2003 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/S1054-3139(03)00045-6
A comparative acoustic-abundance estimation of pelagic redfish (Sebastes mentella) from hull-mounted and deep-towed acoustic systems

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During an international acoustic survey on pelagic redfish (Sebastes mentella) in the Irminger Sea in June–July 2001, a deep-towed vehicle carrying a dual-frequency SIMRAD EK60 Mk1 echosounder was used experimentally to observe and estimate redfish abundance at depths greater than 500 m. Comparison was made with the hull-mounted SIMRAD EK500 echosounder. The deep-towed echosounder improved the spatial resolution of fish in scattering layers as well as the ability to scrutinize and interpret fish echoes. The signal-to-noise ratio was better than that of the hull-mounted system. The fish abundance measured by the deep-towed sounder was consistently high compared to the hull-mounted sounder, particularly, at greater depths. For redfish within the deep scattering layer (DSL), the abundance was, on average, 5% higher, increasing to 55% for redfish below the DSL. From these findings it is concluded that a deep-towed echosounder is superior to hull-mounted ones for estimating the abundance of fish swimming in deep water.

Keywords: deep-towed vehicle; fish-abundance estimation; redfish

Journal Article.  4301 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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