The influence of stock structure and environmental conditions on the recruitment process of Baltic cod estimated using a generalized additive model

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Abstract:

The recruitment process and its underlying mechanisms are among the most studied phenomena in fisheries ecology. Traditional models estimate fish recruitment assuming a direct relationship with spawning stock size. However, highly variable environmental conditions, feeding conditions, and other factors can influence and complicate the results of a simple linear regression analysis between stock and recruitment. We used generalized additive models (GAMs) to investigate the influence of environmental conditions and stock structure on the recruitment processes of Baltic cod. The interaction between abiotic factors and old spawners (>5+ years) and eggs produced by old spawners were the most significant explanatory variables. Eggs produced by young spawners have a positive impact on cod recruitment only at high levels of reproductive volume, while old spawners' eggs have the highest positive effect at low levels of reproductive volume. Here we show: (i) that the number of Baltic cod recruits is strictly dependent on the age structure of the population; (ii) that interactions between biotic and abiotic factors are crucial in explaining recruitment variability; and (iii) that GAMs are a powerful technique for defining and quantifying the intricate multidimensional relationship between biotic and abiotic variables involved in recruitment processes.

Le recrutement et ses mécanismes sous-jacents sont parmi les phénomènes les plus étudiés en écologie des pêches. Les modèles traditionnels estiment le recrutement des poissons en supposant une relation directe avec le stock des reproducteurs. Cependant, les conditions très variables du milieu, les conditions alimentaires et d'autres facteurs peuvent intervenir et complexifier les résultats d'un simple analyse de régression linéaire entre le stock et le recrutement. Nous avons utilisé des modèles additifs généralisés (GAM) pour étudier les effets des conditions environnementales et de la structure du stock des reproducteurs sur le processus de recrutement chez la Morue franche de la Baltique. Les relations entre les facteurs abiotiques et les recruteurs âgés (>5+ ans) et les oeufs produits par ceux-ci se sont révélés les variables explicatives les plus significatives. Les oeufs produits par les jeunes reproducteurs n'ont d'impact positif sur le recrutement que lorsque le volume de reproduction est élevé; en revanche, les oeufs provenant des reproducteurs plus âgés ont une influence positive maximale lorsque le volume de reproduction est limité. Il est donc démontré (i) que le nombre de recrues dans cette population de morues dépend de la structure en âges de la population, (ii) que les interactions entre les facteurs biotiques et abiotiques jouent un rôle crucial dans la variation du recrutement et (iii) que les GAM sont une technique puissante pour définir et quantifier les relations complexes et multidimensionnelles entre les variables biotiques et abiotiques impliquées dans les processus de recrutement.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: December 1, 2000

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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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