Report of the Workshop on a long-term management strategy for Norwegian Spring-s​pawning herring​ (WKNSSHMSE​)

The workshop on management strategy evaluation for the Norwegian spring-spawning herring (Clupea harengus) in subareas 1, 2, and 5, and in divisions 4.a and 14.a, WKNSSHMSE, was convened to prepare the technical basis needed by ICES to respond to the request from NEAFC. The request is listed in Annex 1 of this report. The workshop was given the following terms of reference:
a) Evaluate the proposed harvest control rules (HCRs) for a long-term manage- ment strategy for Herring (Clupea harengus) in subareas 1, 2, 5 and divisions 4.a and 14.a, Norwegian spring-spawning herring (the Northeast Atlantic and Arctic Ocean), as specified in the request and
b) Prepare the first draft of the advice for the special request on NSSH in North East Atlantic.

The workshop addressed the terms of reference and the findings are recorded in this report. The report is organised as follows: The methodological framework is presented in Section 2 while section 3 covers updated work on reference points. Results are found in Section 4 while section 5 presents overall workshop conclusions and section 6 lists the references. Several annexes are included in the report. Annex 1 is the request received by ICES. Annex 2 contains the working documents that were presented to the workshop. Annex 3 contains all summary output tables corresponding to the final results for the evaluation and performance criteria indicated in the request, for the short term, medium term and long term. Annex 4 pro-vides a list of participants and Annex 5 provides the summary table of the HCR eval-uation. Finally, Annex 6 provides a preliminary knowledge quality assessment – this work was not presented at the workshop, but it was decided to include the Annex as it may help guide the appropriate level of precision to report findings in future work using the simulation model and data. Annex 7 includes the reviewers’ reports.

While working with the Management Strategy Evaluation, the group encountered issues with the reference point simulations from earlier this year (ICES, 2018), and therefore these issues have been revisited by WKNSSHMSE. This took considerable time, and since the time schedule for answering the request was already very tight it was decided to prioritize and first focus on issues that were considered most important and then finish the other issues in the request if there was enough time. The plan was, however, to answer all issues in the request if possible.

Unfortunately, during the meeting in Torshavn it became clear that there was not enough time to include all aspects of the Request in detail. Below is a list of deviations from the request and an explanation for the prioritization made:

1) All four rules should be tested without constraint and with two different types of constraint on the inter-annual variation of TAC.
One of the prioritizations made due to time issues was to first test the effect of the TAC constraint only on rule 1 and rule 3 (one F–rule and one HR rule). The reason for prioritizing rule 1 and 3 was that they have the form of the standard ICES MSY rule with F/HR = 0 when SSB = 0 and the results should illustrate the effect on inter-annual vari- ability in catch of including the two different TAC constraints.
2 ) Test the effect of allowing a maximum of 10% to be banked or borrowed any year.

This was unfortunately not done. It was unclear how banking and borrowing should be implemented, and it was decided to prioritize getting the code ready and quality checked for running the simulations with the 8 selected scenarios and to put bank- ing/borrowing on the list of issues that could be done if time allowed after finishing the prioritized issues. In the end, there was no time to do this. Banking/borrowing could, however, be checked at a later stage when clients have decided on a HCR. It should be noted that MSEs for other stocks have shown that the impact of 10% banking or borrowing on the performance of the harvest control rules is insignificant (e.g. flat- fish in North Sea (Brunel and Miller 2013); blue whiting (ICES 2016b); Pandalus (ICES 2016c).

3) The request asks for special cases such as F = 0.102 (FMSY as defined by WKNSSHREF) to be tested.
Due to the issues with the reference points simulations (WKNSSHREF) that were en- countered, the simulations were conducted without the old and new FMSY estimates. These values have, however, been included in the evaluation tables by splining the data (see section 4).

A draft advice for the special request was prepared by the workshop chairs after the workshop.