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dc.contributor.authorAldrin, Magne Tommy
dc.contributor.authorAanes, Fredrik L
dc.contributor.authorTvete, Ingunn Fride
dc.contributor.authorAanes, Sondre
dc.contributor.authorSubbey, Samuel
dc.date.accessioned2021-10-04T09:00:47Z
dc.date.available2021-10-04T09:00:47Z
dc.date.created2021-08-16T18:32:44Z
dc.date.issued2021
dc.identifier.citationFisheries Research. 2021, 243 1-8.en_US
dc.identifier.issn0165-7836
dc.identifier.urihttps://hdl.handle.net/11250/2787395
dc.description.abstractWe consider the challenge in estimating the natural mortality, M, in a standard statistical fish stock assessment model based on time series of catch- and abundance-at-age data. Though anecdotal evidence and empirical experience lend support to the fact that this parameter may be difficult to estimate, the current literature lacks a theoretical justification. We first discuss the estimatability of a time-invariant M theoretically and present necessary conditions for a constant M to be identifiable. We then investigate the practical usefulness of this by estimating M from simulated data based on models fitted to 19 fish stocks. Using the same data sets, we next explore several model formulations of time varying M, with a pre-specified mean value. Cross validation is used to assess the prediction performance of the candidate models. Our results show that a time-invariant M can be estimated with reasonable precision for a few stocks with long time series and typically high values of the true M. For most stocks, however, the estimation uncertainty of M is very large. For time-varying M, we find that accounting for variability across age and time using a simple model significantly improves the performance compared to a time-invariant M. No significant improvement is obtained by using complex models, such as, those with time dependencies in variability around mean values of M.en_US
dc.language.isoengen_US
dc.titleCaveats with estimating natural mortality rates in stock assessment models using age aggregated catch data and abundance indicesen_US
dc.typePeer revieweden_US
dc.typeJournal articleen_US
dc.description.versionpublishedVersionen_US
dc.source.pagenumber1-8en_US
dc.source.volume243en_US
dc.source.journalFisheries Researchen_US
dc.identifier.doi10.1016/j.fishres.2021.106071
dc.identifier.cristin1926444
dc.relation.projectHavforskningsinstituttet: 14809en_US
cristin.ispublishedtrue
cristin.fulltextoriginal
cristin.qualitycode1


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