Benchmark Workshop on the development of MSY advice for category 3 stocks using Surplus Production Model in Continuous Time; SPiCT (WKMSYSYSPICT)

The Benchmark Workshop on the application of SPiCT to produce MSY advice for selected stocks (WKMSYSPiCT) is a unique benchmark in that it is ICES first effort to provide MSY advice for category 3 stocks and it incorporated model learning sessions, with model developers and stock assessors, carried out prior to the data evaluation meeting. Thirteen stocks, including nine de-mersal fish stocks and four Functional Units of Nephrops (Nephrops norvegicus), pertaining to four ICES Assessment Working Groups (WGNSSK, WGDEEP, WGCSE and WGBIE), were selected based on the availability of appropriate data and network capacity. Stock assessments using the Surplus Production in Continuous Time (SPiCT) were successful for two demersal stocks, Me-grim (Lepidorhombus spp.) in Division 6.b (lez.27.6b) and Black-bellied anglerfish (Lophius bude-gassa) in divisions 8.c and 9.a (ank.27.8c9a) and for three Functional Units of Nephrops, Norway lobster FU 25 (nep.fu.25), Norway lobster FU 26–27 (nep.fu.2627) and Norway lobster FU 31 (nep.fu.31). WKMSYSPiCT considered that the stocks´ 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 two Tusk (Brosme brosme) stocks, Tusk in subareas 1 and 2 (usk.27.1-2) and Tusk in subareas 4 and 7-9, and in divisions 3.a, 5.b, 6.a, and 12.b (usk.27.3a45b6a7-912b) and for Norway lobster FU 28–29 (nep.fu.2829), but the available data did not allow to distinguish between two very different stock status. For Pollock (Pollachius pol-lachius) in Subarea 8 and Division 9.a (pol.27.89a), no model configuration passed diagnostics tests. The extensive exploration of input data and model configurations carried out during the workshop resulted in several recommendations regarding the use of historical catches, the stand-ardization of CPUE, including approaches accounting for spatial, target and technological creep effects and, SPiCT model diagnostics.