Calculation of stock weight- and fecundity-at-age during the spawning season used to assess the Northern Contingent of Atlantic Mackerel (Scomber scombrus)

Abstract

The spawning stock of the northern contingent of Atlantic mackerel is currently evaluated with a custom state-space, age-structured stock assessment model. We revised the methods for estimating two key input matrices: stock weight- and fecundity-at-age during the spawning season. The newly calculated weight-at-age did not differ meaningfully from previously used matrices, whereas fecundity-at-age estimates were notably higher and constrained to be less variable than those used in the preceding 2021 assessment. The updated methodology enhances replicability and the revised matrices are considered more biologically realistic. The presented improvements were incorporated into the 2023 assessment, contributing to its accuracy.