Estimating total mortality among fisheries affecting Porbeagle shark (Lamna nasus) in Atlantic Canadian waters
Notice bibliographique
Résumé
Porbeagle Sharks (Lamna nasus) in the northwest Atlantic are currently being considered for listing under the Canadian Species at Risk Act (SARA), and Fisheries and Oceans Canada (DFO) Science was asked to estimate total annual fishing mortality. This would come from landings, and at-vessel mortality (AVM) or post-release mortality (PRM) of discards from fisheries in the Maritimes (MAR), Gulf (GULF), Quebec (QC) and Newfoundland and Labrador (NL) Regions. This evaluation considers 2015 to 2021, representing a time period following the closure of the commercial Porbeagle fishery. Total landings remained low from Atlantic Canadian fisheries, dropping from 3.8 mt in 2015 to less than 200 kg in 2021. The vast majority of landings in 2015–2021 came from longline gear in MAR, primarily benthic longline in the Atlantic Halibut fishery with lower amounts from the pelagic longline fishery for Swordfish and Other Tunas. At-sea observer (ASO) coverage was variable among different fisheries and could not be estimated for fisheries in NL, GULF or QC. When coverage was low (< 5% annually), fisheries observed discards of Porbeagle substantially underestimated fishery-wide totals and needed to be scaled up to annual discard estimates. Also, several fisheries that would be expected to interact with Porbeagle had no ASO coverage and thus could not be considered in this assessment. A suite of statistical estimators was evaluated to model fishery-wide discards for pelagic longline in MAR. However, the data were not sufficient for quantitative models and thus these approaches were not applied. Simple scalars of either the proportion of observed trips (MAR) or proportion of observed target catch (NL) were used to approximate annual fishery wide bycatch from individual fisheries. Although estimates of total mortality were derived from scenarios assuming different AVM and PRM rates for various fisheries, they lacked precision and were predicated on numerous assumptions. Also, there were several factors that would have caused annual mortality to be underestimated but could not be corrected in advance of this assessment, so the magnitude of underestimation was unknown. Given demonstrated challenges and limitations of the available data, it is not possible to derive meaningful estimates of total annual fishing mortality of Porbeagle throughout Atlantic Canadian waters. Interpretation of the implications of observed increases or decreases in annual fishing mortality is not possible without information on underlying abundance and status of infrequently observed, discarded bycatch species (such as Porbeagle). This limits the utility of estimates of fishing mortality to address conservation or management goals and warrants consideration of an alternate framework to quantify threats to bycatch species from fisheries.
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 | 0,002 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,001 |
| Bibliométrie | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 ».