Management strategy evaluation for northern shrimp in the Barents Sea (ICES subareas 1 and 2)

Abstract

To establish a management plan for northern shrimp (Pandalus borealis) in the Barents Sea, the Norwegian-Russian Fisheries Commission requested in 2023 a proposal for a harvest control rule (HCR). Based on discussions with stakeholders, six different HCRs were defined and evaluated against three performance criteria: 1. precautionarity (less than 5% risk of falling below limit reference point for spawning stock biomass, B ), 2. achieving a high longterm sustainable yield, and 3. stability (minimizing median interannual catch variability). All six HCRs were based on a standard hockey-stick HCR that differed only in the role of B (whether fishing ceases at B or not) and the definition of target fishing mortality. To reduce interannual fluctuations in catches, a catch constraint was added that capped year-to-year changes of total catch to 20%. The HCRs were evaluated with a full-loop management strategy evaluation based on the current stock assessment, using a surplus production model parametrized with assessment estimates as operating model and the assessment model SPiCT as observation model. The results showed that only the four HCRs without any fishing below B were precautionary, while the two HCRs with a slope to the origin did not fulfill the precautionary criteria. The four remaining HCRs traded off long-term yield with stability and risk, with the two HCRs where target fishing mortality was set to 80% or 90% of F lim lim lim MSY lim resulting in lower risk and higher stability but also lower median yield. The four HCRs also remained precautionary under a scenario of a substantial decrease in productivity due to environmental change. The northern shrimp stock in the Barents Sea has not been heavily fished over longer periods since the onset of its fishery, representing a challenge for the estimation of the productivity and resilience of the stock at lower biomass levels. This increases the uncertainty of the stock assessment and, subsequently, the management strategy evaluation. Relevant uncertainty is therefore linked to the stock's response to an increase from current catch levels to fishing at or near F MSY , suggesting that constraining the year-to-year increase in total catch is of particular importance when phasing in a management plan. The MSE framework and its results were endorsed at the March meeting 2024 between IMR and VNIRO and evaluated through an external review.