WKICEMSE - Report of the Workshop on Evaluation of the Adopted Harvest Control Rules for Icelandic Summer Spawning Herring, Ling and Tusk
The Workshop on evaluation of the adopted harvest control rules for Icelandic sum-mer spawning herring, ling and tusk (WKICEMSE), chaired by Carmen Fernández, met in Copenhagen, Denmark, during April 21–25 2017. The workshop was attended by nine participants, including two reviewers, from three countries and ICES. The aim of the workshop was to provide the technical basis needed by ICES to respond to the request from Iceland on evaluation of a set of proposed harvest control rules for ling, tusk and herring. The workshop addressed all its terms of reference, with the following main outcomes:
For ling and tusk, a review of the stock assessment methodology was conducted, which resulted in agreed data and model settings for their stock assessment. Precau-tionary Approach and MSY reference points were calculated. The harvest control rules proposed for ling and tusk are based on harvest rates that correspond to yield at or very close to the maximum sustainable yield, while resulting in less than 5% probability of SSB being below Blim. The rules can, therefore, be considered to be precau-tionary and in conformity with the MSY approach.
Several harvest control rules were evaluated for herring. The occurrence of Ichthy-ophonus epidemic outbreaks in recent years, which increase natural mortality, and the uncertainty surrounding the frequency with which outbreaks may occur in future, considerably complicates the evaluation. The rules were evaluated under several sce-narios of frequency of future disease outbreaks. Assessment bias (15% overestimation of stock size) was also considered in the evaluations, based on observed past patterns. All harvest control rules proposed are based on fishing mortalities or harvest rates that correspond to yield at or very close to the maximum sustainable yield. All rules resulted in less than 5% probability of SSB below Blim under scenarios that assume no future Ichthophonus epidemics. Assuming increased mortality due to an Ichthyophonus epidemic in 2017–2019, and the possibility of further outbreaks in future, but no as-sessment bias, all rules resulted in less than 5% probability of SSB below Blim, except in year 2020 for some of the rules. When this Ichthyophonus scenario is combined with 15% assessment bias, the behaviour of the rules differs: two of them remain precau-tionary, for two of them the probability of SSB being below Blim slightly exceeds 5% (6%-8%) in 2019–2021, although it becomes less than 5% in the long run; finally, for one of the rules (the current advisory rule) the probability of SSB below Blim exceeds 5% in most years and the rule cannot be considered precautionary under these condi-tions. All rules except for this one can be considered to be precautionary and in conformity with the MSY approach.
Published under the auspices of the following ICES Steering Group or Committee