Inter-Benchmark Protocol on Celtic Seas Whiting 2021 (IBPCSWhiting)

IBPCSWhiting was primarily tasked with reviewing the data raising procedures after an error was identified during the Celtic Seas working group (WGCSE) in May, causing a subsequent shift in SSB in the early time-series. As this had potential implications for the reference points, the group also updated the stock’s reference points. In preparation of the IBPCSWhiting, a review of ICES Accessions data revealed that a small amount of discard data for Belgium for data year 2019 (79 t) and 2020 (65 t) was available as well as 4.6 t for Spain in data year 2019. These were imported into InterCatch and the IC files for data year 2019 and 2020 only were exported again for use in this IBP. Furthermore, an anomaly was identified in the stock mean weights at age file that had been included at the 2020 benchmark (WKCELTIC). Additional information for catch data prior to 2003 was not available to the WKCELTIC so the 1999–2002 part of the timeseries could not be revised. The catch mean weights-at-age file that was used to generate the Jan 1st stock mean weights at age, contained stock weights in the 1999–2002 rows, while the remaining 2003 onward were correct. The catch and stock mean weights at age files have been corrected for use in this IBP. The assessment model, a State-space Assessment Model (SAM) that is available on stockassessment.org1 was re-run with the revised catch data inputs (additional discard data, re-estimated weights at age, and a revision to the allocation of sampling across catch).