NEAFC request to ICES to evaluate the extra harvest control rule options for the long-term management plan for blue whiting

ICES reaffirms the precautionary reference points given in its response of June 2013 to the special request from NEAFC on the long-term management plan for blue whiting, (Section 9.3.3.1). ICES confirms that the value of F0.1 is currently estimated to be 0.22. ICES advises that the value of FMSY is considered to be 0.30 and this replaces the F0.1 proxy for FMSY of 0.18 from the advice of September 2012 (Section 9.4.4).

For the fixed target Fs of 0.22, 0.25, and 0.30 the HCRs are shown to meet the ICES precautionary requirements of less that 5% probability of SSB< Blim over a ten-year period. The proposed multistage HCRs are shown to meet the ICES precautionary requirement of less that 5% probability of SSB< Blim for the recruitment regimes simulated over a 40-year period (12 years of normal recruitment followed by 8 years of high recruitment and, finally, followed by 20 years of low recruitment).

The request proposes a new multistage HCR with two optional values for a slope parameter (a2). The results of the evaluations showed that the HCRs gave similar performance with both values and no differences could be seen in the plots of SSB and F. The increase in F at high biomass leads to greater catch variability and 4% higher yields over the 40-year period simulated (particularly during periods of high recruitment). The multistage HCR leads to higher interannual variability (IAV) in TAC during the period of declining stock as recruitment changes from the high to the low regime. IAV for the multistage HCR is 33% compared to 25% for the F target of 0.22.

Two extreme cases of banking and borrowing were evaluated (either continually banking or borrowing the full allowable amount). Both showed negligible differences in terms of F, SSB, or probability of SSB< Blim.

The advice for TAC levels (2014) according to the different target F options (0.22, 0.25, and 0.30) outlined in this request were also provided in the advice issued in October 2013 (Section 9.4.5). For the multistage HCR with either slope option the target F for 2014 is 0.30, which is also provided as a catch option in the October 2013 Advice.