1. A state-space spatial survey-based stock assessment (SSURBA) model to inform spatial variation in relative stock trends
- Author
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Kumar, Rajeev, Cadigan, Noel G., Zheng, Nan, Varkey, Divya A., and Morgan, M. Joanne
- Subjects
Fishes -- Models -- Research ,Stocks -- Research -- Models ,Earth sciences - Abstract
An age-structured, spatial survey-based assessment model (SSURBA) is developed and applied to the Grand Banks stock (NAFO Divisions 3LNO) of American plaice (Hippoglossoides platessoides) in Newfoundland and Labrador. The state-space model is fit to annual spatial (i.e., three divisions) stock size-at-age research vessel (RV) survey indices that are assumed to be proportional to abundance. We model index catchability (q) as a logistic function of fish length, which varies with age, cohort, and the time of the survey; therefore, the model facilitates the estimation of q values that change spatially and temporally following changes in fish growth and survey gears. The SSURBA model produces division-level estimates of fishing mortality rates (F), stock productivity, and stock size relative to the logistic catchability assumption with q = 1 for fully selected ages. The spatial model allows us to include additional survey information compared with the space-aggregated assessment model (all of 3LNO) that is currently used to assess stock status. The model can provide estimates of relative catch, which we compare with reported catch trends to partially validate the model. Un modele devaluation base sur des releves spatiaux structures par age (SSURBA) est mis au point et utilise pour le stock des Grands Bancs (divisions 3LNO de l'OPANO) de plies canadiennes (Hippoglossoidesplatessoides) a Terre-Neuve-et- Labrador. Le modele d'espace d'etats est cale sur des indices de releves par navire de recherche (NR) de l'age selon la taille du stock qui sont presumes proportionnels a l'abondance. Nous modelisons la capturabilite indexee (q) en tant que fonction logistique de la longueur des poissons, qui varie selon l'age, la cohorte et le moment du releve; ainsi le modele facilite l'estimation de q qui varient dans l'espace et le temps a la suite de changements de la croissance des poissons et des engins utilises pour les releves. Le modele SSURBA produit des estimations au niveau de la division des taux de mortalite par peche (F), de la productivite du stock et de la taille du stock au vu de l'hypothese de capturabilite logistique pour q = 1 pour des ages entierement selectionnes. Le modele spatial nous permet d'inclure plus d'information tiree des releves que ce que permet le modele devaluation spatialement regroupe (ensemble des 3LNO) actuellement utilise pour evaluer l'etat du stock. Le modele peut fournir des estimations des prises relatives que nous comparons aux tendances des prises rapportees afin de valider partiellement le modele. [Traduit par la Redaction], Introduction Canadian fisheries management has a long history of conducting scientific surveys to monitor fish populations, with some of the earliest surveys dating back to the 1970s (Halliday and Fanning [...]
- Published
- 2020
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