Report of the ​Workshop on the scientific basis for the advice for 2018 for Norwegian Spring Spawning Herring (WKADVNSSH)​

The Workshop on the scientific basis for the advice for 2018 for Norwegian Spring Spawning Herring (WKADVNSSH) was held at the ICES HQ during 4–5 December 2017. It was chaired by Guðmundur J. Óskarsson (Iceland) and included total 16 participants (10 by correspondence) representing 8 countries.

• The ToR was to review the assessment and the forecast that formed the basis for ICES advice on fishing opportunities for Norwegian spring spawning herring in 2018.
• A WD was presented (Annex 3) posing questions about the changes on the forecast made at ADGWIDE and the assessment after the error in the Survey 1 was observed: - The pattern in the selection for 2017 and 2018 concerned the ADG, which requested a further explanation on why the model was predicting this. There was behaviour that could not be explained regarding the forecast, so it was considered correct to follow a more 'standard' approach. - The correction of Survey 1 led to less conflict in signals between Surveys 1 and 5, leading to XSAM results that gave slightly better fit to the data. - The WG acknowledge the relevance of the questions raised with respect to alternative configurations of the input data of the assess-ment, while concluding that some of these issues were either addressed during the 2016 benchmark and/or should be addressed during a future benchmark assessment (e.g. inclusion of other surveys, the age range of the assessment etc.).
• Following a presentation and discussion on the changes in the forecast procedure that impacted the advice during the ADG, the majority of the WKADVNSSH gave their support to the decision and concluded that it had scientifically sound justification. In 2016, using the benchmark procedure, the selectivity pattern did not show the drastic change observed this year. This was possibly because of the large change in TAC from 2016 to 2017 and also because the age structure of the population has shifted to older fish. Given that it could not be clearly explained how the model was predicting the future changes in selectivity, the ADG’s decision to adopt an approach more in line with the 'standard' forecast procedure used in ICES assessments was supported by the majority of the group.
• The importance of transparent feedback between the drafting group and the assessment group was acknowledged.  This is crucial for the transparency of the advice process, and ACOM have already developed plans to improve the communication between ADGs and WGs for the coming advice year.