The Workshop on the Benchmark of Rockall haddock (Melanogrammus aeglefinus) (WKROCK), chaired by Helen Dobby (UK) for ICES and External Chair, Alexander Kempf (Germany), took place 2–5 April 2019. Other participants in the meeting included scientists from the UK and the Russian Federation, and external reviewers from Canada and France. This stock had never be-fore been through the benchmarking process and therefore there were a significant number of both data and modelling issues to be addressed.

Given the limited time available and the time spent preparing input data at the meeting, the workshop focused more on a review of the current assessment rather than on advancing the assessment and subjecting it to a complete review of data inputs, modelling assumptions and an examination of the advice consequences of alternate model runs. The main focus of the WK was how to estimate stock weights from the very uncertain (and increasing) mean weight-at-age in the catch and in addition how best to deal with changes in the survey design (of the tuning index) including an expansion to cover a greater portion of the stock distribution. It was agreed that stock weights would be best modelled as a five year running average of catch weights. The WK agreed to maintain the approach adopted by the assessment WG for dealing with the survey data i.e. making use of a single series based on the original survey area, due to a much poorer retro-spective when the new survey series was included as a separate index (most likely due to theshort time-series).

A further outcome of the workshop was that XSA assessment, which had previously been con-ducted using the Lowestoft VPA suite, was implemented in FLXSA, facilitating the management strategy evaluation required in the second part of this benchmarking process.

Future research and data requirements were also identified in consultation with the external re-viewers.