Exploring the population dynamics of winter skate (Leucoraja ocellata) in the Georges Bank region using a statistical catch-at-age model incorporating length, migration, and recruitment process errors

نویسندگان

  • M. G. Frisk
  • K. Sosebee
چکیده

Winter skate (Leucoraja ocellata) of all length classes increased dramatically in abundance on Georges Bank in the 1980s following the decline of many groundfish species. We present a full population model of winter skate to better understand the population dynamics of the species and elucidate the mechanisms underlying their increase in abundance in the 1980s. Specifically, we developed four statistical catch-at-age models incorporating length-frequency data with the following model structures: (i) observation error only (base model R1); (ii) observation and recruitment process errors (model R2); (iii) adult migration modeled as a random walk in adult mortality (model R3); and (iv) observation and recruitment process errors and adult migration (model R4). Akaike’s information criterion values indicated that models R3 and R4, which both included adult migration, were the most parsimonious models. This finding strongly suggests that the winter skate population increase on Georges Bank in the 1980s was not solely a result of increases in recruitment but likely involved adult migration (i.e., it is an open population). Finally, recent predicted fishing mortalities exceeded FMSY for all models. Résumé : L’abondance des raies tachetées (Leucoraja ocellata) de toutes les classes de longueur s’est accrue de façon spectaculaire sur le banc George durant les années 1980 après le déclin de plusieurs espèces de poissons de fond. Nous présentons un modèle démographique complet de la raie tachetée afin de mieux comprendre la dynamique de population de l’espèce et de mettre en évidence les mécanismes sous-jacents de son augmentation en abondance dans les années 1980. En particulier, nous avons mis au point quatre modèles statistiques des captures en fonction de l’âge qui incorporent les données de fréquence des longueurs dans les structures de modèle suivantes : (i) avec seulement l’erreur d’observation (modèle de base R1), (ii) avec les erreurs de traitement des observations et du recrutement (modèle R2), (iii) avec la migration des adultes modélisée comme un cheminement aléatoire dans la mortalité adulte (modèle R3) et (iv) avec les erreurs de traitement des observations et du recrutement et la migration adulte (modèle R4). Les valeurs du coefficient d’information d’Akaike indiquent que les modèles R3 et R4, qui incluent tous les deux la migration des adultes, sont les plus parcimonieux. Cette constatation laisse fortement croire que l’accroissement de la population des raies tachetées sur le banc George dans les années 1980 n’est pas le résultat seulement d’augmentations du recrutement, mais qu’il implique vraisemblablement une migration des adultes (la population est donc ouverte). Enfin, les mortalités dues à la pêche prédites récemment dépassent FMSY dans tous les modèles. [Traduit par la Rédaction]

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تاریخ انتشار 2010