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dc.contributor.authorHjellvik, Vidar
dc.contributor.authorGodø, Olav Rune
dc.contributor.authorTjøstheim, Dag
dc.date.accessioned2007-06-06T11:44:35Z
dc.date.issued2002
dc.identifier.issn0706-652X
dc.identifier.urihttp://hdl.handle.net/11250/108806
dc.description.abstractThe diurnal bias of bottom trawl survey catches is studied with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty and thus increases the variance of the resulting abundance estimate. To investigate this adequately, we use a stochastic model describing diurnal fluctuations and examine the annual variation of the diurnal amplitude as a function of species and length. The diurnal amplitude is fairly stable for large fish, and for these, the bias-corrected estimate leads to a moderate increase in variance. For small fish, the diurnal amplitude is unstable, however, and the correction of diurnal bias occurs at the expense of a large increase in variance. This unstable amplitude also leads to a large year-to-year variation in catchability for small fish. For haddock (Melanogrammus aeglefinus), the diurnal amplitude depends heavily on fish length, indicating a strong decrease in catchability with decreasing fish length.en
dc.format.extent4892314 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoengen
dc.subjectBarents Seaen
dc.subjectbottom trawlen
dc.subjectBarentshavet
dc.subjectbunntrål
dc.titleDiurnal variation in bottom trawl survey catches: does it pay to adjust?en
dc.typeJournal articleen
dc.typePeer reviewed
dc.source.pagenumber33-48en
dc.source.volume59en
dc.source.journalCanadian Journal of Fisheries and Aquatic Sciencesen
dc.source.issue1
dc.identifier.doihttp://dx.doi.org/10.1139/F01-193


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