Journal Article

<i>In situ</i> target strength of the Baltic Sea herring and sprat

Tomas Didrikas and Sture Hansson

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 61, issue 3, pages 378-382
Published in print January 2004 | ISSN: 1054-3139
Published online January 2004 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2003.08.003
In situ target strength of the Baltic Sea herring and sprat

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Using single- and split-beam hydroacoustic equipment (70 and 38 kHz), and gillnet and trawl catches, we derived the relationship TS = 25.5 log10 L − 73.6 (r2=0.95) between acoustic target strength (TS) and fish length (L, cm) for Baltic Sea herring (Clupea harengus membras L.) and sprat (Sprattus sprattus balticus (Schneider)). Fixing the slope to 20, which is a standard practice in hydroacoustics, gave TS = 20 log10 L − 67.8 (r2=0.91). Normally, the fisheries agencies around the Baltic use a TS–length relationship that is based mainly on data from the North Sea and the intercept-value in this equation is 3.4 dB lower than that reported in this paper. This difference corresponds to an approximately twofold difference in assessed stock biomass.

Keywords: Baltic Sea; fat content; herring; hydroacoustics; in situ target strength; salinity; sprat

Journal Article.  3111 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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