Vitenskapelig artikkel

Prediction–variance relation in a state-space fish stock assessment model

Breivik, Olav Nikolai Risdal; Berg, Casper Willestofte; Nielsen, Anders


Tidsskrift: ICES Journal of Marine Science, vol. 78, p. 3650–3657–7, 2021

Utgivere: Oxford University Press

Utgave: 10

Internasjonale standardnumre:
Trykt: 1054-3139
Elektronisk: 1095-9289


The state-space assessment model (SAM) is extended by allowing a functional relationship between observation variance and the corresponding prediction. An estimated relationship between observation variance and predicted value for each individual observation allows the model to assign smaller (or larger) variance to predicted larger log-observations. This relation is different from the usual assumption of constant variance of log-observations within age groups. The prediction–variance link is implemented and compared to the usual constant variance assumption for the official assessments of North East Arctic cod and haddock. For both of these stocks, the prediction–variance link is found to give a significant improvement.