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Benchmark workshop on application of Stock Synthesis (SS3) on selected stocks (WKBSS3) is the first dedicated ICES benchmark workshop to stocks assessed using only Stock Synthesis models (SS). Four stocks were included in the ToRs (ank.27.8c9a; Black-bellied anglerfish (Lophius budegassa) in divisions 8.c and 9.a, Cantabrian Sea, Atlantic Iberian waters; mon.27.8c9a; White anglerfish (Lophius piscatorius) in divisions 8.c and 9.a, Cantabrian Sea and Atlantic Iberian waters, pol.27.67; Pollack (Pollachius pollachius) in subareas 6-7; Celtic Seas and the English Channel; sbr.27.9; Blackspot seabream (Pagellus bogaraveo) in Subarea 9; Atlantic Iberian waters. The stocks pertain to three ICES Assessment Working Groups (WGBIE, WGCSE, and WGDEEP) and were selected based on the availability of appropriate data and network capacity.Stock assessments using SS models were successful for all stocks and accepted by WKBSS3 as adequate to provide advice. Preliminary SS assessment runs were already presented and discussed during the data meeting and in a dedicated 1-day meeting on the 10th of February. Except pollack, all stocks were assessed using sex separated models including Blackspot seabream for which the model was also accounting for sex change (proterandric hermaphroditic). Several model configurations were tested for each stock based on a grid of uncertainty built on hypothesis testing. The different model configurations to be used to select the “BestCase” model for advice were compared using model diagnostics. The overarching strategy to select the “BestCase” model for advice was based on model diagnostics as described by ICES guidelines. The key model diagnostics used were runs test and RMSE for the analysis of the residuals, retrospective analysis and hindcasting cross validation. Once the “BestCase” model has been selected, additional model diagnostics as jittering and likelihood profiling were also used.Reference points (i.e. FMSY and MSY Btrigger) were estimated using ICES standard procedures with Eqsim and a full-feedback loop simulations tool for reference points estimation (FLRPE) developed in line with WKREFNEW recommendations. Eqsim derived FMSY was compared to alternative level of fishing mortality using FLRPE but maintaining both Blim and MSY Btrigger as in Eqsim. A very similar machinery has been already used for deriving reference points for Central Baltic herring (ICES 2023) and Northern shrimp (ICES 2022). FLRPE has the clear advantage compared to a flat simulation as implemented in Eqsim as it emulates an annual update of the benchmark assessment model by passing outcomes (SSB and F) from the ‘true’ age-structured dynamics from the operating model (OM) with assessment error to the harvest control rule (HCR) and catch implementation system. The feedback control loop between the implementation system and the OM allows accounting for the lag between the last of year data used in the assessment and the implementation year of catch advice. Moreover, it has the ability to retain the two-sex structure of the original assessment models, when present. The comparison between Eqsim and FLRPE highlighted that Eqsim FMSY is not precautionary or will result in loss of yields and therefore Eqsim should not be used for deriving reference points in the future or should be always tested against a full-feedback loop simulations tool for reference points estimation as FLRPE.For Black-bellied anglerfish in divisions 8.c and 9.a, Cantabrian Sea, White anglerfish in divisions 8.c and 9.a, Cantabrian Sea and Atlantic Iberian waters and Pollack in subareas 6-7; Celtic Seas and the English Channel, Eqsim estimated FMSY was not precautionary when tested using FLRPE and therefore it was rejected and FLRPE estimated FMSY was adopted. For Blackspot seabream (Pagellus bogaraveo) in Subarea 9; Atlantic Iberian waters, Eqsim estimated FMSY was precautionary when tested using FLRPE. However, Eqsim estimated FMSY was larger than FMSY estimated by the model and therefore FMSY was based on the value estimated internally by the Stock Synthesis model. Specifically, for White anglerfish, the selected Fadv is 0.75Fmsy.Btri.eq, corresponding to 0.355 (less than 5% risk, same catches than 0.775Fmsy.Btri.eq). For Black-bellied anglerfish, the selected Fadv is 0.95Fmsy.Btri.eq, corresponding to 0.173 (less than 5% risk). For pollack, the selected Fadv is 0.90Fmsy.Btri.eq, corresponding to 0.278 (less than 5% risk and less than 1% reduction in long-term catch compared to Fmsy.Btri.eq). For Blackspot seabream, the selected Fadv is 1Fmsy.Btri.eq, corresponding to 0.099 (less than 5% risk; same FMSY as estimated by Stock Synthesis and same catches as Fmsy.eq.Btri.eq). It is also important to note that for White anglerfish, a lower F down to 0.284 will result in a loss of 3% of the catches with almost 40% more SSB at equilibrium; For Black-bellied anglerfish, a lower F down to 0.118 will results in a loss of 5% of the catches with more than 50% SSB at equilibrium. For pollack, a lower F of 0.214 results in a loss of 4% the long-term catch with a 20% increase in long-term SSB under the full recruitment scenario. For Blackspot seabream, a lower F down to 0.056 will result in a loss of about 5% of the catches with more than 50% SSB.Finally, forecast settings to be used during the incoming update assessment during spring were presented and agreed.

Nyckelord

WGBIE; WGCSE; WGDEEP; black-bellied anglerfish; White Anglerfish; Pollack; Blackspot seabream

Publicerad i

ICES scientific reports
2025, nummer: 7:25
Utgivare: International Council for the Exploration of the Sea

SLU författare

UKÄ forskningsämne

Vilt- och fiskeförvaltning

Publikationens identifierare

  • DOI: https://doi.org/10.17895/ices.pub.28443992

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/141675