Science Advisory Report 2024/048

*This advice was developed in a peer review meeting in 2020 and should be interpreted within the context of the situation at that time.

Science Advice on a Performance Threshold for the Management Strategy Evaluation for Southwest Nova Scotia/Bay Of Fundy Atlantic Herring (Clupea harengus)

Summary

• Potential performance thresholds for the Southwest Nova Scotia/Bay of Fundy Atlantic Herring stock were evaluated to ensure that the selection of a management procedure in the Management Strategy Evaluation (MSE) process be consistent with the objectives of DFO’s Fishery Decision-Making Framework Incorporating the Precautionary Approach (PA Policy).
• The performance threshold is to be used in the Management Strategy Evaluation (MSE) to identify candidate management procedures that result in a high probability of spawning stock biomass (SSB) remaining above the threshold during the projection period.
• Several empirical and theoretical approaches were identified as potential thresholds.
• Empirical approaches were based on a historical biomass from which the stock has recovered or remained stable, as well as a biomass below which recruitment dynamics are unknown.
• Theoretical approaches were evaluated for defining an equilibrium biomass at a fishing mortality rate based on the concepts of maximum sustainable yield, yield-per-recruit or spawning stock biomass-per-recruit, and replacement fishing mortality rate, as well as methods based on unfished biomass.
• The suite of operating models (OMs) implemented in the MSE represent a broad range of simulated stock recruitment dynamics. It was agreed that a theoretical approach for defining the threshold is more consistent with the simulated population dynamics in each OM and thus a more comparable performance metric across OMs.
• A threshold was defined as 70% of the SSB at maximum sustainable yield, 0.7 SSB_MSY.
• The recommended probability and time period to apply the performance threshold in the MSE was P(SSB > 0.7 SSB_MSY) > 75% in each year beginning in year 10 of the 25-year projection period.
• A dynamic SSB_MSY is to be used for evaluating the performance of management procedures in the MSE. The dynamic SSB_MSY was estimated separately for each simulation using annual time-varying growth, maturity, and selectivity, as well as the annual simulation specific recruitment deviations.
• It was recommended that the dynamic SSB_MSY be used only in the evaluation of management procedures in the closed-loop simulations and not used for evaluating stock status.

This Science Advisory Report is from the November 12–13, 2020 and January 18, 2021 regional advisory meeting on the Identification of a Limit Reference Point for Southwest Nova Scotia/Bay of Fundy Atlantic Herring (Clupea harengus). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2024/048 (PDF, 840 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.