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The complex relationship between weight and length of Atlantic cod off the south coast of Newfoundland

Publication: Canadian Journal of Fisheries and Aquatic Sciences
3 October 2022

Abstract

The relationship between the length and weight of fish is used to assess their growth and condition. This relationship is often assumed to be the same spatially and temporally. However, variability in the weight–length relationship can occur, which provides important information about stock productivity. We developed a spatiotemporal model for the weight–length relationship that is useful for predictions in un-sampled areas. We applied the model to survey data for Atlantic cod off the southern coast of Newfoundland, Canada. We found that weight-at-length was higher inshore, oscillated over time, was below average in recent years, declined during late-January to early-June especially for intermediate sized cod, and that the temporal oscillations were correlated with several local environmental time series. Finally, the model estimated a decrease in the allometric coefficient for intermediate sized cod (40–80 cm), indicating that those cod may be experiencing additional feeding deficiencies. Spatiotemporal variation in the weight-at-length relationship should be accounted for in the stock assessment process when fishery catch numbers are derived from tonnes landed and when estimating stock and fishery weights-at-age.

Résumé

La relation entre la longueur et le poids des poissons est utilisée pour évaluer leur croissance et leur embonpoint. Il est souvent tenu pour acquis que cette relation demeure la même dans le temps et l’espace. Une variabilité de la relation poids–longueur est toutefois possible, qui fournit de l’information importante sur la productivité des stocks. Nous élaborons un modèle spatiotemporel pour la relation poids–longueur pouvant être utilisée pour établir des prédictions pour les régions non échantillonnées. Nous appliquons ce modèle à des données d’évaluation pour la morue au large de la côte sud de Terre-Neuve (Canada). Nous constatons que le poids selon la longueur est plus grand dans la zone côtière, oscille dans le temps, est inférieur à la moyenne ces dernières années, baisse de la fin janvier au début de juin, en particulier pour les morues de taille intermédiaire, et que les oscillations temporelles sont corrélées à plusieurs séries chronologiques de variables environnementales locales. Enfin, le modèle produit une baisse estimée du coefficient d’allométrie pour les morues de taille intermédiaire (40–80 cm) qui indique que d’autres déficiences alimentaires pourraient affecter ces morues. Les variations spatiotemporelles de la relation du poids selon la longueur devraient être prises en compte dans le processus d’évaluation de stocks quand les chiffres sur les prises des pêches sont dérivés des tonnes débarquées et pour l’estimation des poids selon l’âge dans des stocks et des pêches. [Traduit par la Rédaction]

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Information & Authors

Information

Published In

cover image Canadian Journal of Fisheries and Aquatic Sciences
Canadian Journal of Fisheries and Aquatic Sciences
Volume 79Number 11November 2022
Pages: 1798 - 1819

History

Received: 23 November 2021
Accepted: 31 May 2022
Accepted manuscript online: 9 June 2022
Version of record online: 3 October 2022

Data Availability Statement

The data that support the findings of this study are available from the authors upon reasonable request.

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Key Words

  1. spatiotemporal model
  2. condition
  3. cluster analysis
  4. productivity dynamics

Mots-clés

  1. modèle spatiotemporel
  2. embonpoint
  3. analyse typologique
  4. dynamique de la productivité

Authors

Affiliations

Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, P.O. Box 4920, St. John’s, NL A1C 5R3, Canada
Author Contributions: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, and Writing – review & editing.
Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, P.O. Box 4920, St. John’s, NL A1C 5R3, Canada
Author Contributions: Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing – original draft, and Writing – review & editing.
Kunasekaran Nirmalkanna
Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, P.O. Box 4920, St. John’s, NL A1C 5R3, Canada
Author Contributions: Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing – original draft, and Writing – review & editing.
Nan Zheng
Centre for Fisheries Ecosystems Research, Fisheries and Marine Institute of Memorial University of Newfoundland, P.O. Box 4920, St. John’s, NL A1C 5R3, Canada
Author Contributions: Conceptualization, Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing – original draft, and Writing – review & editing.

Author Contributions

NC conceptualization, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, supervision, validation, visualization, writing – original draft, writing – review & editing; MR formal analysis, investigation, methodology, software, validation, visualization, writing – original draft, writing – review & editing; KN formal analysis, investigation, methodology, software, validation, visualization, writing – original draft, writing – review & editing; NZ conceptualization, formal analysis, investigation, methodology, software, validation, visualization, writing – original draft, writing – review & editing.

Competing Interests

The authors declare there are no competing interests.

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