Benchmark workshop 2 on development of MSY advice using SPiCT (WKBMSYSPiCT2)

Benchmark workshop 2 on development of MSY advice using SPiCT (WKBMSYSPiCT2) is the second effort to provide MSY advice for stocks previously assessed as category 3 stocks, which also incorporated model learning sessions, with model developers and stock assessors, carried out prior to the data workshop. Ten stocks, including nine demersal fish stocks and one elasmobranch, pertaining to five ICES Assessment Working Groups (WGNSSK, WGWIDE, WGCSE, WGEF, and WGBIE), were selected based on the availability of appropriate data and network capacity. Stock assessments using the stochastic Surplus Production in Continuous Time (SPiCT) model were successful for two demersal finfish stocks, brill (Scophthalmus rhombus) in Subarea 4 and divisions 3.a and 7.d–e (bll.27.3a47de) and pollack (Pollachius pollachius) in Subareas 6–7 (pol.27.67); and one elasmobranch thornback ray (Raja clavata) in Division 8.c (rjc.27.8c). Plaice (Pleuronectes platessa) in divisions 7.f and 7.g (ple.27.7fg) and whiting (Merlangius merlangus) in Division 3.a (whg.27.3a) were ultimately not presented during the benchmark. For Whiting (Merlangius merlangus) in Subarea 8 and Division 9.a (whg.27.89a), the analysis was limited to evaluating the available input data for the application of category 3 methods during the benchmark. WKBMSYSPiCT2 considered that those stocks with an accepted SPiCT assessment model, the current category could be upgraded since the methodology is appropriate to determine stock status and a short-term catch forecast. Several model configurations were applied for the remaining stocks under assessments, but the available data did not allow distinguishing between very different, yet equally plausible stock status states and/or the models failed to produce acceptable diagnostics tests. The extensive exploration of input data and model configurations carried out during the workshop resulted in several recommendations regarding the standardization of commercial CPUE, including approaches accounting for spatial, target and technological creep effects and SPiCT model settings. Finally, for stocks where it was not possible to develop a SPiCT model, the use of integrated models could be explored as an alternative in future to account for the good amount of length and biological information available for these stocks