Jack mackerel management procedure: draft decision guide
Proposed advice and decisions for discussion before Commission consideration
Results working paper · Retained-CMP scorecard · All-CMP scorecard · Jack mackerel wiki
This guide proposes a route from the current scientific comparison to a Commission decision. The shortlist, responsibilities and wording are proposed for review by the Scientific Committee, Commission and Parties. They draw on the saved 500-simulation results in the companion working paper. Selection of a management procedure remains a decision for the Commission.
1 Proposed advice for the next discussion
Candidate management procedures (CMPs) are rules for turning monitoring information into catch advice. Operating models (OMs) represent possible stock and fishery conditions; robustness tests check the rules under alternative assumptions.
Carry HS−20 (MP43), HS−30 (MP47) and PR−20 (MP44) forward as a small set for focused scientist–manager discussion. They preserve the contrast between catch stability, the ability to make larger advice reductions, and the power-ramp response. Use the fixed-catch run as a reference comparison. Keep the full CMP set available so that an omitted alternative can be reinstated if agreed objectives or robustness tests justify it.
The immediate recommendation is to agree the criteria for selecting among these alternatives. Choosing a preferred CMP depends on managers’ priorities. A score of 100 marks the best selected value for an indicator. Biological acceptability also requires an agreed risk limit.
1.1 Suggested wording for consideration
The Scientific Committee is invited to consider carrying HS−20, HS−30 and PR−20 forward for focused consultation, subject to review of the screening criteria and remaining projection checks. The comparison should present reference-OM performance and separate recruitment-crash (OM11_2) and recruitment-cycle (OM11_3) robustness results, with near-term 2026–2035 trade-off and Kobe plots. Managers are invited to specify the biological performance requirements and the relative importance of catch, catch variability and the ability to reduce advice. A subsequent recommendation for a preferred CMP should state these choices, identify the supporting results and specify implementation, responses to unexpected conditions and review arrangements.
This wording proposes a process and a set of CMPs for discussion. Confirming that these CMPs meet biological requirements will require an agreed standard and a check of their performance against it.
The advice-reduction update changes the earlier screening result: HS+20, HSsym, PR+20 and PRsym now show trade-offs with the listed comparators. The three-CMP display remains a discussion set, and all eight CMPs should be reviewed before confirming the shortlist.
2 Why retain these alternatives?
IACC measures annual catch variability. SSB is spawning-stock biomass, and Blim is the biomass limit. “Green” means biomass and fishing pressure meet the stated MSY reference levels; the definitions below explain the time period and changing biomass reference.
| Alternative | Management choice it helps examine | Results and points to consider |
|---|---|---|
| HS−20 (MP43) | Greater emphasis on stable catches, retaining the 20% advice-reduction limit. | Lower reference IACC than PR−20; compare the biological consequences as well as stability in the reference trade-offs. |
| HS−30 (MP47) | Whether allowing larger advice reductions provides a worthwhile biological benefit. | Lower reference below-previous-Blim frequency than HS−20, with a different frequency of advice reductions greater than 19%. Review both outcomes in the reference comparison. |
| PR−20 (MP44) | Whether higher reference catch and its biological performance justify greater catch variability. | Highest long-term dynamic-green probability among these three in recruitment crash (54.5%) and recruitment cycle (51.5%). See the focused robustness results. |
| Fixed catch | What is gained or lost by responding to observations rather than holding advice constant. | A reference comparison; evaluation under the alternative OMs would be needed before considering it alongside the finalists. Its saved recruitment deviations, implementation adjustments and MSY values differ from the other reference runs; see the comparison limits. |
For this stage, retaining contrasting alternatives is more defensible than selecting the top three from one composite ranking. This approach keeps the main choices visible while leaving room to revisit alternatives with useful advantages. If managers prefer numerical ranking, first agree the indicators, weights and biological requirements, then check whether the preferred CMP changes with those choices and with OM selection. The scorecards support this exploration. A systematic check of how rankings change with the selected weights and OMs remains to be completed.
3 Decisions and actions to record
The following division of responsibilities is proposed for discussion. The final process and the Party or Parties tabling a Commission proposal remain to be agreed.
| Decision | What needs to be recorded | Results or next action |
|---|---|---|
| 1. Biological objectives | Target status, limit definition, acceptable risk, assessment period, and whether requirements apply to each stock component or to an aggregate. | Scientists should express each requirement as a reproducible statistic; managers should confirm the required performance. Keep the current 60% dynamic-green tuning convention distinct from any newly requested target. |
| 2. Role of robustness tests | Which scenarios determine acceptability, which inform contingency planning, and any agreed OM weights. | Review recruitment crash (OM11_2) and recruitment cycle (OM11_3) separately. Compare the near-term 2026–2035 displays with long-term outcomes; agree a method before combining results across OMs. |
| 3. Shortlist and preferences | Whether to retain these three CMPs; which differences matter; whether any composite weights are agreed. | Review the full-set scorecard and screening tolerances. Retain or reinstate an alternative if it offers a relevant advantage under the agreed criteria. |
| 4. Stability and response | Allowed increases and decreases in advice, management-cycle length, implementation lag and any phase-in provisions. | Distinguish advice limits from realized-catch variability. Evaluate any changed settings before recommending the revised package. |
| 5. Preferred CMP | Exact CMP identifier, tuning and settings; reasons for choosing it; material disadvantages accepted. | Scientists should document performance against agreed criteria. A Party proposal could then identify the preferred package for Commission consideration. Delegations would state their preferences during that process. |
| 6. Implementation and review | Required data and deadlines, responsibility for running and checking the MP, first application, missing-data procedures, response to unexpected conditions, and scheduled review. | Prepare an implementation plan alongside the proposal. Agree when a review is required, who will conduct it, and a timetable suited to SPRFMO. |
4 Definitions that must accompany the advice
Tuning and risk answer different questions. Here, dynamic-green results concern SSB at or above dynamic BMSY and F at or below FMSY over the stated 2041–2050 period. The probability of staying above a biomass limit throughout the period requires a separate calculation. The figures labelled SSB/SSBMSY describe biomass relative to the stored, fixed reference value; dynamic-green probabilities use a reference value that changes with productivity.
Count years below a limit and simulations with a breach separately. The existing SSB <8% dynamic B0 statistic is the fraction of simulation-years below the previous Blim. If managers instead require the probability of at least one breach during a specified period, that statistic must be calculated separately. The 8% threshold represents the previous Blim for this comparison. Managers still need to confirm the limit and acceptable risk for adoption.
Advice reductions cover all annual comparisons. CatchDrop20 now reports the percentage of valid comparisons in which HCR advice falls strictly more than 19%, pooled across all years and 500 iterations. Exact 20% reductions count, and no biomass filter is applied. This measures advice before implementation; realized-catch variability remains available separately. The first advice is compared with the saved HCR initial advice, or the constant target for fixed catch, giving 25 years × 500 iterations = 12,500 comparisons. See the working paper for denominators and the two-stock advice convention.
5 Work needed before recommending adoption
- Confirm the biological requirements and how robustness outcomes affect selection. If these differ from the evaluated settings, rerun or retune the affected comparisons.
- Complete the remaining projection checks and document the results, including low-catch failures and advice-versus-realized-catch discrepancies. The revised advice statistic does not resolve underlying projection problems.
- Review the new 2026–2035 trade-off and Kobe plots alongside long-term summaries. A separate first-application reduction distribution would further inform implementation.
- If fixed catch is proposed as an adoption candidate, evaluate it under comparable recruitment and implementation assumptions and the required robustness set. Its present role is a reference comparison.
- Hold a focused scientist–manager and stakeholder discussion, record preferences and remaining disagreements, and prepare a preferred-CMP proposal with a complete implementation and review specification.
6 How the supplied examples inform this guide
The ICCAT Atlantic bluefin decision guide (2022), especially pages 3–4, 7 and 24, separates safety, stock status, management cycle, stability, MP choice and review. It links these choices to performance tables and an interactive results application. Its safety statistic concerns the lowest depletion within each simulation over a defined period; that is different from our frequency of years below a limit. This guide follows that sequence of decisions. SPRFMO would agree its own thresholds, scoring method and review interval.
The IOTC bigeye MP adoption document (2022), especially printed pages 1 and 3–5, compares two remaining CMPs by their practical advantages, then asks the Commission to choose a tuning objective and an MP. It refers implementation and exceptional-circumstances arrangements to supporting documents. This supports keeping the main decision guide short while linking the detailed results and specifying the remaining actions.
Review of the supplied ICES download link awaits access to the file, and review of the draft supplement awaits a copy. The proposals above draw on the two documents reviewed. Their application to jack mackerel was developed for this guide.
7 Document status and source files
Prepared 9 September 2026 from the linked public examples and the existing CMP working paper. This guide adds proposed decision language. The wording was revised for clarity on 9 September 2026; calculations and management choices are unchanged. Editable Quarto source is supplied for review. Open policy choices are stated as decisions rather than filled with assumed agreements.