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

ICES has evaluated the reference points and concluded that Blim and Bpa should remain unchanged. New values of Fpa = 0.32 and Flim = 0.48 have been provided that are consistent with these biomass reference points. The corresponding MSY reference points are FMSY = 0.30 and MSY Btrigger = 2.25 million t. The current management plan is considered precautionary. A number of alternative F targets in the range of 0.1–0.35 were evaluated for the current harvest control rule (HCR) form and found to be precautionary up to an F target of 0.32 (corresponding to Fpa), with only a minimal increase in mean TAC for F targets above 0.3. Inclusion of catch stabilization mechanisms have been tested in the current HCR and are considered precautionary as they do not increase the probability of SSB< Blim above 0.05. Over the entire time period examined there are no significant differences in catch either with or without the stabilizers. The 50–50 rule may lead to considerably reduced interannual variation (IAV), but can generate high Fs during periods of stock decline and lower catches during periods of stock increase. Initial evaluations indicate that a number of options for the newly proposed HCR form (with increasing F at high biomass) have been found to be precautionary. However, these preliminary evaluations are not considered sufficiently robust. Based on the results presented, ICES suggests that a small subset of such rules should be selected and tested further with greater rigour before they are judged suitable for precautionary management. Testing of banking and borrowing scenarios showed very little impact of either extreme banking or borrowing. Allowing a maximum of 10% to be banked or borrowed any year is considered precautionary when used with the existing HCR.