| Summary: | WKBWNSSH evaluated the Long Term Management Plan for Norwegian spring spawning herring following the request from the Coastal States, where particularly implementing FMSY = 0.15 and investigating harvest control rule taking into account recent recruitment were emphasized. In addition, the reference points associated with the current management plan were asked to be evaluated. Precautionary reference point Blim was estimated using segmented regression method using several assessment years and time periods of stock-recruitment pairs. The breakpoint value, below which recruitment is considered to become impaired, varies depending on assessment year and time period used. However, the analysis suggests that the current Blim of 2.5 million tonnes lies within all confidence intervals, even though many of the estimates are higher than the current Blim. WKBWNSSH does not recommend changing Blim, but encourages further analyses, particularly using all the available historical data. Evaluation of the different harvest control rule options was performed using a stochastic simulation model. The model simulates the biological stock, i.e., the true stock, and the observed stock, i.e., the perceived stock. The model was run for 98 years, whereof short term (first 5 years), medium term (first 10 years and years 6 to 15), long term (first 50 years) and stationary equilibrium (last 50 years) averages over 1000 replicate runs were calculated. The results from all except the last 50 years are influenced by the initial conditions. Seven Harvest Control Rule (HCR) options were examined: HCR 1: The current management plan (option A in the request), HCR 2: Current management plan modi-fied with using FMSY = 0.15 (option B in the request), HCR 3: F depends on recent recruitment (option C in the request), HCR 4: Current management plan modified with zero-F at zero-SSB (option A2 in the request), HCR 5: FMSY plan modified with zero-F at zero-SSB (option B2 in the request), HCR 6: F depends on recent recruitment with zero-F at zero-SSB ...
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