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- Title
In situ target strength of the Baltic Sea herring and sprat
- Authors
Didrikas, Tomas; Hansson, Sture
- Abstract
Using single- and split-beam hydroacoustic equipment (70 and 38 kHz), and gillnet and trawl catches, we derived the relationship <f>TS=25.5 log10 L-73.6</f> (<f>r2=0.95</f>) 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 <f>TS=20 log10 L-67.8</f> (<f>r2=0.91</f>). 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.
- Subjects
BALTIC herring; SPRAT; UNDERWATER acoustics; GILLNETTING
- Publication
ICES Journal of Marine Science / Journal du Conseil, 2004, Vol 61, Issue 3, p378
- ISSN
1054-3139
- Publication type
Article
- DOI
10.1016/j.icesjms.2003.08.003