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Differences in juvenile phenotypes and survival between hatchery stocks and a natural population provide evidence for modified selection due to captive breeding

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Juvenile phenotypes and fitness as indicated by survival were compared for naturally produced steelhead (Oncorhynchus mykiss), a new local hatchery stock, and an old nonlocal hatchery stock on the Hood River, Oregon, U.S.A. Although the new hatchery stock and the naturally produced fish came from the same parent gene pool, they differed significantly at every phenotype measured except saltwater age. The characteristics of the new hatchery stock were similar to those of the old hatchery stock. Most of the phenotypic differences were probably environmentally caused. Although such character changes would not be inherited, they may influence the relative fitness of the hatchery and natural fish when they are in the same environment, as selection responds to phenotypic distributions. A difference in fitness between the new hatchery stock and naturally produced fish was indicated by significant survival differences. Acclimation of the new hatchery stock in a “seminatural” pond before release was associated with a further decrease in relative smolt-to-adult survival with little increase in phenotypic similarity between the natural and hatchery fish. These results suggest that modified selection begins immediately in the first generation of a new hatchery stock and may provide a mechanism for genetic change.

Les phénotypes des jeunes et leur survie (comme mesure de fitness) ont pu être comparés chez des truites arc-en-ciel anadromes (Oncorhynchus mykiss) nées en nature, des truites d'un nouveau stock local de pisciculture et des truites d'un ancien stock non local de pisciculture dans la rivière Hood, Oregon, É.-U. Bien que le nouveau stock de pisciculture et le stock naturel proviennent du même pool génétique parental, ils différent significativement par tous les caractères phénotypiques mesurés, sauf l'âge en eau salée. Les caractéristiques du nouveau stock de pisciculture ressemblent à celles de l'ancien stock de pisciculture. La plupart des différences phénotypiques sont probablement attribuables à l'environnement. Bien que de tels caractères ne soient pas transmis génétiquement, ils peuvent affecter le fitness relatif des poissons de pisciculture et des poissons sauvages quand ils cohabitent dans le même milieu, puisque la sélection réagit à la distribution des phénotypes. Il existe des différences significatives de survie, donc de fitness, entre le nouveau stock de pisciculture et le stock sauvage. L'acclimatation du nouveau stock de pisciculture dans un étang « semi-naturel » avant sa libération en nature entraîne une diminution additionnelle de la survie des saumoneaux jusqu'au stade adulte et augmente peu la ressemblance phénotypique entre les poissons de pisciculture et les poissons sauvages. Ces résultats indiquent que la sélection modifiée agit immédiatement dès la première génération dans un nouveau stock de pisciculture et qu'elle peut fournir un mécanisme pour le changement génétique.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: April 1, 2004

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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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