This paper outlines the key parameters and their uncertainty ranges for management strategy evaluations (MSE) for Antarctic toothfish in the Ross Sea region. It focuses on the parameters that influence assessment outcomes and hence management advice. This identifies critical parameters requiring initial evaluation, including natural mortality, recruitment patterns, growth parameters, tagging-related parameters, maturity, selectivity patterns, and bias in tag-related abundance estimates. For each parameter, we provide plausible ranges derived from previous assessments and meta-analyses (where other information is inadequate to provide a plausible range) to test the robustness of alternative harvest control rules.
While no increasing or decreasing trends have been observed for recruitment for Antarctic toothfish in the Ross Sea region, changes in the level of mean recruitment may be expected to occur in the future due to climate-induced shifts in oceanographic conditions or ecosystem regime shifts. The proposed framework incorporates stochastic recruitment scenarios to test policy resilience against gradual and abrupt population dynamics shifts, aligning with CCAMLR's precautionary ecosystem-based management framework.
This approach optimises scientific resource allocation by prioritising evaluation of the most influential uncertainties first, providing a practical framework for evaluating alternative harvest control rules while supporting progressive refinement through subsequent research phases.
We recommend:
- Prioritised parameter evaluation: Focus first on parameters with the greatest influence on assessment outcomes and management advice, particularly natural mortality, recruitment dynamics, and tag-related parameters.
- Comprehensive uncertainty characterisation: Define the plausible ranges and distributions for those parameters, and observations from the fishery or other stocks for parameters where currently available analyses do not inform uncertainty ranges.
- Stochastic recruitment scenarios: Develop scenarios that test management strategy robustness against potential changes in recruitment patterns due to climate or ecosystem shifts, including changes in the level of mean recruitment.
- Where uncertainty ranges for parameters cannot be determined, evaluate monitoring approaches to instigate breakout or stopping rules if changes in these parameters are detected.
- Adaptive approach: Implement the MSE in phases, allowing for refinement and additional parameter exploration as new data and research results become available.