Framework review for 4X5Y Haddock : operating model specification, projections, simulation approach, and reference points

Abstract

The 4X5Y Haddock stock assessment model was rejected in 2018 due to large retrospective patterns and a mismatch between model-estimated biomass and survey biomass. Catch advice has since been provided qualitatively based on the DFO ecosystem survey index. In 2023, DFO science began a framework for a new assessment method for the 4X5Y Haddock stock, which included a review of the data inputs and the development of assessment models. Three assessment models were identified and are presented in this document with different hypotheses to explain the mismatch between fishery and survey data inputs: density dependent natural mortality (Models 1 and 2) and constant natural mortality with random effects on the stock numbers-at-age transitions (Model 3). Reference points were defined for each model and weighted to provide an overall stock status. Two sets of operating models were defined based on these three models to account for uncertainty in future stock productivity. One set assumed status quo productivity with no large recruitment events, and the other assumed productivity consistent with the last 25 historical years and includes a large recruitment event consistent with the 2013 cohort. A management procedure (MP) evaluation framework using closed-loop simulation is presented in this document and was used for evaluating the performance of MPs relative to management objectives. Example management procedures were used in this document to demonstrate how the MP evaluation framework will be applied. When an MP meets the minimum performance standard defined for conservation objectives, tradeoffs among MPs for all objectives can be evaluated. This MP evaluation framework can be used in the future to select an MP to provide catch advice for the 4X5Y Haddock fishery. Exceptional circumstances are defined to address situations outside the range of scenarios for which the MP was simulation tested or when the data required to apply the MP are not available.