Long-term trends of bloater (Coregonus hoyi) recruitment in Lake Michigan: evidence for the effect of sex ratio

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Abstract:

Long-term population trends are generally explained by factors extrinsic (e.g., climate, predation) rather than intrinsic (e.g., genetics, maternal effects) to the population. We sought to understand the long-term population dynamics of an important native Lake Michigan prey fish, the bloater Coregonus hoyi. Over a 38-year time series, three 10- to 15-year phases occurred (poor, excellent, and then poor recruitment) without high interannual variability within a particular phase. We used dynamic linear models to determine whether extrinsic (winter and spring temperature, alewife predator densities) or intrinsic factors (population egg production, adult condition, adult sex ratio) explained variation in recruitment. Models that included population egg production, sex ratio, winter and spring temperature, and adult bloater condition explained the most variation. Of these variables, sex ratio, which ranged from 47% to 97% female across the time series, consistently had the greatest effect: recruitment declined with female predominance. Including biomass of adult alewife predators in the models did not explain additional variation. Overall our results indicated that bloater recruitment is linked to its sex ratio, but understanding the underlying mechanisms will require additional efforts.

Les tendances démographiques à long terme s'expliquent généralement par des facteurs extrinsèques à la population, tels que le climat ou la prédation, plutôt que par des facteurs intrinsèques, comme la génétique ou les effets maternels. Nous avons tenté de comprendre la dynamique de population à long terme d'un poisson proie indigène d'importance au lac Michigan, le cisco de fumage, Coregonus hoyi. Dans une série chronologique de 38 ans, il s'est produit trois phases de 10–15 ans, de recrutement faible, excellent et de nouveau faible, sans grande variation entre les années durant une phase donnée. Des modèles dynamiques linéaires nous ont servi à déterminer si la variation du recrutement s'explique par des facteurs extrinsèques (températures de l'hiver et du printemps, densité des prédateurs) ou intrinsèques (production d'oeufs de la population, condition des adultes, sex-ratio des adultes). Les modèles qui incluent la production d'oeufs de la population, le sex-ratio, les températures d'hiver et de printemps et la condition des ciscos adultes expliquent le maximum de variation. De ces variables, le sex-ratio, qui va de 47 à 97 % dans la série chronologique, a régulièrement l'effet le plus prononcé : le recrutement diminue lorsque les femelles prédominent. L'addition de la biomasse des prédateurs, les gaspareaux adultes, dans le modèle n'explique pas de variation supplémentaire. Dans leur ensemble, nos résultats indiquent que le recrutement du cisco de fumage est relié au sex-ratio, mais il faudra faire des travaux additionnels pour comprendre les mécanismes sous-jacents.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: April 1, 2006

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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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