Model validation for the selection and weighting of stock assessment scenarios

This worked example has been conducted in response to the Recommendation that the Shark Species Group, together with the Working Group on Stock Assessment Methods, should help develop guidelines for the selection, rejection, weighting and extension of stock assessment models when providing robust management advice. The blue shark assessment, in common with other ICCAT stock assessments, has to consider alternative often conflicting data sets, uncertain life history information, and auxiliary data sets such as length and tagging data. The Working Group on Stock Assessment Methods has therefore recommended that Species Groups should identify model uncertainties, biases and misspecifications, to be considered when specifying uncertainty grids to be considered. The Shark Species Group has also been asked to provide, “... options for a harvest control rule (HCR) with associated limit, target and threshold reference points for the management of blue shark in the ICCAT Convention area”.