Report of the Inter-Benchmark Protocol for Blue Whiting (IBPBLW)
The Inter-Benchmark Protocol of Blue Whiting (IBPBLW) convened by correspondence from 10 March to 10 May 2016. The meeting was chaired by Patrícia Gonçalves. There were 16 participants from eight countries; 13 scientists and three representing the industry. One independent scientist from outside the ICES community participated in the process and reviewed the conclusions of the inter-benchmark protocol. The participant list is in Annex 1.
The main purpose of the meeting was to evaluate the robustness of the SAM model in situations with clear "year effects" in survey indices as observed in the 2015 International Blue Whiting Spawning Stock Survey (IBWSSS). The use of catches-in numbers- at-age for the first one or two quarters in the assessment year should be explored both in terms of getting more realistic F in the intermediate year and also on the retrospective pattern seen for the stock. Since the benchmark in 2012, recruitment indices from several surveys have been used qualitatively to predict the year-class size (small, medium, large). Now an attempt should be made to model the indices. Finally Biological Reference Points should be re-evaluated.
The IBPBLW agreed on using a newly developed option for the SAM model as the standard assessment (model 3c). This option takes account to correlation of observations.
The IBPBLW concluded that preliminary age-disaggregated catches from the first two quarters (Q1+Q2) in the assessment year were preferable over only catches from quarter 1. They give a more realistic F in the intermediate year, but do not affect the retrospective pattern in the assessment.
The review of recruitment indices was not finished. More work will be done before WGWIDE in August 2016.
IBPBLW pointed out that there is an ongoing management strategy evaluation (MSE) for blue whiting. Reference point evaluations should preferably be tightly connected to the MSE, because harvest control rules and reference points inherently go together. Therefore reference points were not re-evaluated by IBPBLW
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