Implementing ageing errors in the SAM assessment of North Sea turbot and Northeast Atlantic mackerel (KB-36-002-042)

Ageing errors can substantially reduce the accuracy of fish stock assessments, but yet, they are not taken into account for the vast majority of the stocks. A recent ICES initiative (WKAMEMSA 2021) reviewed to the information available on ageing errors, possible effects on assessment and the new developments in stock assessment models to incorporate these, and identified potential case studies in which ageing errors could be incorporated in the assessment. This project aims at covering two of these case studies, North Sea turbot and Northeast Atlantic mackerel, both assessed by WMR, using the SAM stock assessment model. The outcome of this project will be considered in future benchmarks and therefore potentially lead to modifications of the stock assessment methodology and improved management of the stocks.