Diurnal variation in acoustic densities: why do we se less in the dark?

Introduction: In the Barents Sea, the echo abundance of demersal fish is about 50% higher at day than at night. Three possible reasons are: • Fish hide in the bottom dead zone at night. • Fish target strength changes due to pressure-related swim-bladder changes during vertical migration. • Fish targ...

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Bibliographic Details
Main Authors: Hjellvik, Vidar, Godø, Olav Rune, Tjøstheim, Dag
Format: Report
Language:English
Published: ICES 2004
Subjects:
acoustics
akustikk
stock assessment
bestandsberegning
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
Barents Sea
Online Access:http://hdl.handle.net/11250/106609
id ftimr:oai:imr.brage.unit.no:11250/106609
record_format openpolar
spelling ftimr:oai:imr.brage.unit.no:11250/106609 2023-05-15T15:38:45+02:00 Diurnal variation in acoustic densities: why do we se less in the dark? Hjellvik, Vidar Godø, Olav Rune Tjøstheim, Dag 2004 application/pdf http://hdl.handle.net/11250/106609 eng eng ICES ICES CM Documents;2004/R:33 This report is not to be cited without prior reference to the authors http://hdl.handle.net/11250/106609 1 s. acoustics akustikk stock assessment bestandsberegning VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924 Working paper 2004 ftimr 2021-09-23T20:15:20Z Introduction: In the Barents Sea, the echo abundance of demersal fish is about 50% higher at day than at night. Three possible reasons are: • Fish hide in the bottom dead zone at night. • Fish target strength changes due to pressure-related swim-bladder changes during vertical migration. • Fish target strength varies due to higher variation in the tilt-angle distribution at night. It is very often claimed that the dead zone is most important. We argue that variation in tilt-angle may also be important. Report Barents Sea Institute for Marine Research: Brage IMR Barents Sea
institution Open Polar
collection Institute for Marine Research: Brage IMR
op_collection_id ftimr
language English
topic acoustics
akustikk
stock assessment
bestandsberegning
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
spellingShingle acoustics
akustikk
stock assessment
bestandsberegning
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
Hjellvik, Vidar
Godø, Olav Rune
Tjøstheim, Dag
Diurnal variation in acoustic densities: why do we se less in the dark?
topic_facet acoustics
akustikk
stock assessment
bestandsberegning
VDP::Agriculture and fishery disciplines: 900::Fisheries science: 920::Fisheries technology: 924
description Introduction: In the Barents Sea, the echo abundance of demersal fish is about 50% higher at day than at night. Three possible reasons are: • Fish hide in the bottom dead zone at night. • Fish target strength changes due to pressure-related swim-bladder changes during vertical migration. • Fish target strength varies due to higher variation in the tilt-angle distribution at night. It is very often claimed that the dead zone is most important. We argue that variation in tilt-angle may also be important.
format Report
author Hjellvik, Vidar
Godø, Olav Rune
Tjøstheim, Dag
author_facet Hjellvik, Vidar
Godø, Olav Rune
Tjøstheim, Dag
author_sort Hjellvik, Vidar
title Diurnal variation in acoustic densities: why do we se less in the dark?
title_short Diurnal variation in acoustic densities: why do we se less in the dark?
title_full Diurnal variation in acoustic densities: why do we se less in the dark?
title_fullStr Diurnal variation in acoustic densities: why do we se less in the dark?
title_full_unstemmed Diurnal variation in acoustic densities: why do we se less in the dark?
title_sort diurnal variation in acoustic densities: why do we se less in the dark?
publisher ICES
publishDate 2004
url http://hdl.handle.net/11250/106609
geographic Barents Sea
geographic_facet Barents Sea
genre Barents Sea
genre_facet Barents Sea
op_source 1 s.
op_relation ICES CM Documents;2004/R:33
This report is not to be cited without prior reference to the authors
http://hdl.handle.net/11250/106609
_version_ 1766370055960920064

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