Stock status and management procedure performance for the BC Sablefish (Anoplopoma fimbria) fishery for 2022/23

Abstract

The British Columbia Sablefsh fshery has been managed using a simulation tested harvest strategy since 2011. The operating model used to generate simulated stock and fshery data is revised at intervals to refect new data and hypotheses about the management system. We use this paper to detail the migration of the Sablefsh operating model (SAB-OM) from the unsupported AD model builder (ADMB) language to the leading-edge Template Model Builder (TMB) language. We detail a rigorous transition and bridging analysis between 2018 and 2021 data and hypotheses, as well as testing against several sensitivities, including at-sea release model assumptions, age composition likelihood weightings, and leading parameter prior distributions. At the same time, we also transition the Schaefer production model used to estimate biomass and operational control points within the Sablefsh management procedure (MP) from ADMB to TMB, and re-evaluate performance of the updated MP against operational fshery objectives. Sablefsh biomass, productivity, and stock status for 2022, estimated over an ensemble of fve SAB-OM ‘reference set’ hypotheses, indicate that the stock is currently not overfshed and not experiencing overfshing. The spawning biomass at the start of 2022 is approximately 132% of optimal biomass BMSY , and the 2021 harvest rate is about 71% of UMSY , with recent dynamics driven by three large incoming year classes. Estimates of recruitment deviations from the base SAB-OM hypothesis are compared to environmental indices, but no signifcant relationships are evident, indicating that a more in-depth research project may be required to determine if a link exists that would have implications for operating model formulation or management procedure design. Finally, all tested Sablefsh MPs, including the status-quo MP with a 5.5% harvest rate, meet the biomass conservation and target objectives across the reference set of operating models, satisfying Canada’s precautionary approach harvest policy requirements for management by reference points.