| Quantity | Previous assessment (2025 value) | Updated assessment (2026 value) | Change (2026 minus 2025) |
|---|---|---|---|
| SSB | 490.867 | 466.951 | -23.916 |
| Depletion | 0.172 | 0.165 | -0.008 |
| B_Bmsy | 0.521 | 0.497 | -0.024 |
| Catch | 140.001 | 133.001 | -7.000 |
| RY | 104.865 | 98.766 | -6.099 |
| Catch_RY | 1.335 | 1.347 | 0.012 |
Namibian hake model update, 2026
Executive summary
Summary of changes in assessment inputs
The accepted 2025 model configuration was extended through 2026 without changing the base-model assumptions. The update adds the 2026 catch, CPUE, survey biomass, and composition rows provided in namhakdata26.dat. The species-specific survey series in CapeHakes.csv was extended through 2026 for Merluccius paradoxus and M. capensis.
Automated checks confirmed continuous annual ADMB matrices from 1964 through 2026, the expected dimensions of all weight, catch, composition, CPUE, and survey blocks, agreement among all terminal-year controls, and valid 54321 and 12345 end-of-file sentinels.
Summary of results
The 2026 base model converged with an objective function of -44.977, a maximum gradient of 4e-05, and a positive-definite Hessian. Estimated terminal spawning biomass was 467 and terminal spawning biomass relative to BMSY was 0.497.
Four of six sensitivity configurations met the same convergence criteria as the base model. The dome-shaped selectivity case had parameters on their lower bounds and a singular Hessian. The model with steepness fixed at 0.5 had a maximum gradient above 0.001 after an extended optimization. Results from those two configurations are not used for inference.
No TAC, ABC, or OFL recommendation is made in this document. Those quantities require the agreed Namibian management procedure and management inputs.
Introduction
This operational update applies the 2025 base-model structure to information available through 2026. Stable model methods are not repeated in full; the emphasis is on new inputs, bridge results, model diagnostics, and sensitivity to the principal structural assumptions considered in the previous assessment.
Fishery and management history
The assessment input contains annual catches from 1964 through 2026. Management-history text and the final 2026 management decision should be inserted following review by MFMR.
TODO: add the final 2026 TAC decision and any in-season management changes.
Data
| Check | Result |
|---|---|
| Annual model years | 1964–2026 |
| Weight-at-age dimensions | 63 × 10 |
| Fishery composition dimensions | 63 × 11 |
| CPUE dimensions | 63 × 7 |
| Survey dimensions | 63 × 5 |
| Control EOF sentinel | 54321 |
| Data EOF sentinel | 12345 |
Survey data
Other data
No additional external data series were introduced in this update. Missing survey observations remain represented as missing or zero according to the existing model input convention; no values were imputed to create artificial annual continuity.
Analytic approach
The age-structured ADMB model and 2025 base assumptions were retained. The control file specifies the terminal year in four locations: the model terminal year, final selectivity period, final recruitment-estimation year, and final Ksp period. All four are set to 2026.
The bridge comparison changes only the data and terminal year. Sensitivities fix survey catchability at 1.0 and 0.5, estimate natural mortality, allow dome-shaped fishery selectivity, and fix stock-recruit steepness at 0.5 and 0.9. Convergence requires a finite objective, maximum gradient no greater than 0.001, and a positive-definite ADMB Hessian.
Results
Bridge comparison
Model diagnostics and sensitivities
| Model | Objective | Maximum gradient | Status |
|---|---|---|---|
| 2025 baseline | -44.15933 | 0.00023 | Converged |
| 2026 update | -44.97733 | 0.00004 | Converged |
| q = 1.0 | -25.52259 | 0.00006 | Converged |
| q = 0.5 | 32.89469 | 0.00003 | Converged |
| Estimated M | -45.62760 | 0.00007 | Converged |
| Dome selectivity | -46.56746 | 2.49472 | Failed diagnostic criteria |
| h = 0.5 | -53.76517 | 0.00302 | Failed diagnostic criteria |
| h = 0.9 | -33.47065 | 0.00008 | Converged |
Projections and harvest recommendations
The ADMB model produced replacement-yield and long-term reference-point outputs for each converged configuration. A management recommendation is not presented because the final control-rule inputs and decision framework were not supplied as part of this update.
TODO: insert the agreed harvest-control-rule calculation and resulting TAC advice after management review.
Risk table and recommendation
The 2026 base model passed the declared numerical diagnostics. Structural uncertainty remains material: estimated natural mortality and fixed survey catchability change the inferred scale of the stock, while the dome-shaped selectivity case is not estimable under the current parameterization. The non-converged h = 0.5 and dome-selectivity results should not be assigned inferential weight.
Status determination
The base-model estimate of spawning biomass relative to BMSY is reported in Table 1. Formal legal or management status terminology should be supplied by MFMR using the applicable Namibian framework.
Ecosystem considerations
No new ecosystem covariates were incorporated in the assessment likelihood. The species-specific survey series is retained for evaluating the relative signals for M. paradoxus and M. capensis.
Data gaps and research priorities
- Resolve the non-identifiability of dome-shaped selectivity before using that alternative for management inference.
- Profile or otherwise investigate the
h = 0.5optimization surface. - Document the provenance and preprocessing of each annual input block.
- Add retrospective analyses and likelihood profiles to the operational workflow.
- Archive the final management-procedure inputs alongside the accepted assessment.
Acknowledgements
The assessment update was prepared by John Kathena and Jim Ianelli with data provided by the Namibian Ministry of Fisheries and Marine Resources.
Auxiliary files
The assessment source, annual controls, automated validation tests, ADMB template, and model outputs are maintained in the NamibianHake repository.