How reliable are the abundance indices derived from commercial catch–effort standardization?

Authors: Ye, Yimin; Dennis, Darren

Source: Canadian Journal of Fisheries and Aquatic Sciences, Volume 66, Number 7, July 2009 , pp. 1169-1178(10)

Publisher: NRC Research Press

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Abstract:

Commercial catch-per-unit-effort (CPUE) data are often standardized to construct indices of stock abundance. The value of such standardization lies in the improvement in the proportionality between the derived index and true abundance. Using the Torres Strait rock lobster (Panulirus ornatus) fishery in Australia as an example, we first standardized the commercial CPUE data using a generalized linear model (GLM) and then fitted observation error models to the resulting abundance indices and independent abundance data (as estimated by research diver surveys) to examine the proportionality. While the GLM standardization greatly improved proportionality in comparison with the nonstandardized commercial catch rates, it could produce biased results if the model did not explicitly incorporate variables that had caused changes in fishing efficiency. As most catch–effort standardizations do not model the fishing power component simultaneously, this result may serve as a warning to the potential bias in stock abundance indices extracted from GLMs that are underfitted.

On standardise souvent les captures commerciales par unité d’effort (CPUE) afin d’obtenir des indices d'abondance des stocks. L’intérêt d’une telle standardisation consiste en l’amélioration de la proportionnalité entre l’indice obtenu et la véritable abondance. En nous servant de l’exemple de la pêche commerciale de la langouste ornée (Panulirus ornatus) du détroit de Torres en Australie, nous avons d’abord standardisé les données de CPUE de la pêche commerciale à l’aide d’un modèle linéaire généralisé (GLM) et nous avons ensuite ajusté les modèles d’erreurs d’observation aux indices d’abondance obtenus ainsi qu’à des données d’abondance indépendantes (estimées par des inventaires de recherche par des plongeurs) afin d’évaluer la proportionnalité. Bien que la standardisation par GLM améliore considérablement la proportionnalité par rapport aux taux de capture commerciale non standardisés, elle peut produire des résultats erronés si le modèle n’incorpore pas de façon explicite les variables responsables des changements de l’efficacité de la pêche. Puisque la plupart des standardisations de la capture–effort ne modélisent pas en même temps la composante de la puissance de la pêche, nos résultats peuvent servir d’avertissement de l’existence d’une erreur potentielle dans les indices d’abondance des stocks obtenus par des GLM sous-ajustés.

Document Type: Research Article

Publication date: July 1, 2009

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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