22nd Regular Session of the Scientific Committee

SC22 will assess whether an expanded OM grid sufficiently captures plausible states of nature for robust MSE testing, including the treatment of key uncertainties, overlap-area assumptions, fisheries outside MP control, and consistency with the updated 2026 stock assessment framework, and determine readiness for formal adoption of the bigeye tuna OM framework.

• SC21 reviewed and supported an initial reference set of 24 bigeye tuna operating models developed under SC21-MI-WP-05 and noted that the OM grid captures key uncertainties such as recruitment variability, steepness, tag mixing, and effort creep, providing a suitable basis for initial testing. However, SC21 noted that the OM grid produces a relatively narrow range of outcomes, particularly for historical depletion, with much of the uncertainty driven by recruitment assumptions, indicating that the full range of plausible stock dynamics may not be adequately represented. SC21 therefore recommended further refinement and expansion of the OM reference set before formal adoption, including incorporation of additional high-priority uncertainties such as growth, natural mortality, movement dynamics, spatial structure, and potential CPUE hyperstability, as well as broader uncertainties related to domestic and archipelagic fisheries and climate change.

  Consistent with WCPFC22 guidance and outcomes from BMW01, further OM development should also consider the treatment of uncertainties in archipelagic fisheries, fisheries outside MP control, overlap-area implementation issues, and alternative assumptions for fisheries not directly controlled by the BET MP through structured sensitivity analyses, while maintaining a tractable OM grid. BMW01 further agreed that assumptions for fisheries outside MP control should generally use fixed recent catch or effort levels depending on the spatial option evaluated.