Stock assessment of NAFO divs. 2J3KL cod
Notice bibliographique
Résumé
The Newfoundland and Labrador climate experiences important fluctuations at decadal time scales, with potential impacts on ecosystem productivity. These large scale changes are linked to phases of the North Atlantic Oscillation (NAO) and patterns in large-scale ocean circulation (e.g., increased Labrador Current transport). The coldest period on record (late 1980s to early-1990s) coincided with the Northern cod stock collapse and has been linked to significant changes in the ecosystem. Warmer than average conditions have been observed over the last three years. Primary (phytoplankton) and secondary (zooplankton) productivity have improved to near or above average levels since around 2015, but with changes in zooplankton seasonality (lower spring, higher summer and fall biomass signals) and community structure (higher dominance of small-sized copepods). Ecosystem conditions in the Newfoundland Shelf and Northern Grand Bank (NAFO Divs. 2J3KL) remain indicative of overall limited fish community productivity, with low abundance of key forage species and total Research Vessel (RV) trawl survey biomass remaining well below pre-collapse levels. Diet composition of cod and other key predators indicate food limitation. Increases in groundfish observed from the mid-2000s to mid-2010s were associated with bottom-up processes, but have stalled as key forage species like Capelin and Shrimp have declined. Cod productivity has been linked to Capelin levels. Given the forecasted levels of Capelin for the next two years, the prospects for cod stock growth appear limited. The Newman Sound pre-recruit index suggests that cohorts from 2018 to 2020 will be weaker than those in the past ten years and the pre-recruit index is well below the mean of those in the 25-year time series. The stock is being assessed using an integrated model (Northern Cod Assessment Model, NCAM), which allows quantification of uncertainty in estimated and projected stock status. The estimate of Spawning Stock Biomass (SSB) in 2021 is 411 kt (95% CI = 307–549 kt). SSB currently remains in the critical zone, at 52% (95% CI = 39–69%) of the Limit Reference Point (LRP). The stock has remained at about the same level since 2017. Natural mortality rate (M) estimated from NCAM for ages 5+ for 2020 was 0.51 (95% CI = 0.30–0.89). The average M over the last 10 years was 0.39 (range = 0.29 to 0.63). The fishing mortality rate (F) estimated from NCAM for ages 5+ is currently low, and for 2020 was 0.018 (95% CI = 0.014–0.024). The average F over the last 10 years is 0.02 (range = 0.014 to 0.028). Recruitment (age 2) estimated from NCAM increased from the lowest estimated levels of 34 million fish in 1995 to an average of 314 million per year for cohorts from 2015 to 2019. This recent average is 25% of the pre-collapse period of the 1980s. A one year projection from NCAM with catch ranging from zero to 1.3 times (15,360 t) the model estimated catch for 2020 (11,816 t) indicated that the probability that SSB will reach the LRP by 2022 is <0.02. The probability of the stock being greater in 2022 than in 2021, across all catch scenarios examined ranged from 0.52 to 0.59. The calculation of the Harvest Decision Rule (HDR) for this stock in accordance with the Northern Cod Rebuilding Plan indicates removals for 2021 of 12,999 t for stewardship fishery catch. When accounting for the recreational fishery these removals are likely to fall at, or above, the upper range of catch scenarios examined. Consistency with the DFO decision-making framework incorporating the precautionary approach requires that removals from all sources must be kept at the lowest possible level until the stock clears the critical zone.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,002 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».