Model-based estimates of reference points in an age-based state-space stock assessment model

Abstract

Reference points are central in the current management of marine living resources. However, reference points are estimated from data and model estimates. Therefore, they are inherently uncertain. We present two objective methods for estimating reference points and quantifying their uncertainty. The first method uses per-recruit calculations, while the second method relies on a long-term forecast of the managed system. Confidence intervals are calculated through a combination of the implicit function theorem and the delta method. Both methods are illustrated for 12 recruitment models using data from the Northeast Arctic cod assessment. Finally, the methods are validated in a simulation study.