Publication Date:
2007-07-24
Description:
Johnsen, E., and Godø, O. R. 2007. Diel variations in acoustic recordings of blue whiting (Micromesistius poutassou). – ICES Journal of Marine Science, 64: 1202–1209. Annual landings of blue whiting (Micromesistius poutassou) in the northeast Atlantic have exceeded 2 million metric tonnes in recent years, and overexploitation is an increasing concern in terms of the sustainability of the fishery. The most important fisheries-independent dataset used for tuning the analytical stock assessment comes from the Norwegian surveys of blue whiting west off the British Isles. The survey is carried out in March/April during peak spawning, and improving its quality will have a direct positive effect on stock assessment. Here, we analyse diel effects on the abundance and vertical distribution as recorded by acoustics in 1995 and 1996 and from 1998 to 2002, and evaluate the potential effects on the survey estimates. On average, the acoustic density of blue whiting was ∼20% higher by day than by night. However, the diel bias varied considerably among years, and surprisingly, the acoustic density in shallow water (
Print ISSN:
1054-3139
Electronic ISSN:
1095-9289
Topics:
Biology
,
Geosciences
,
Physics
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