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Changes in run timing and natural smolt production in a naturally spawning coho salmon (Oncorhynchus kisutch) population after 60 years of intensive hatchery supplementation

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Supplementing natural fish populations with artificially propagated (hatchery) fish is a common practice. In evaluating supplementation, it is important to assess the relative fitness of both hatchery-produced and naturally produced fish when they spawn together in the wild and to evaluate how the absolute fitness of the natural population changes after many generations of supplementation. We evaluated the relative fitness of naturally produced and hatchery-produced coho salmon (Oncorhynchus kisutch) in Minter Creek, Washington, USA. We also evaluated long-term changes in natural smolt production in this stream after several decades of intensive hatchery supplementation. Total smolt production was estimated to be 14 660 and 19 415 in 2002 and 2003, respectively, compared with the average value of 28 425 from 1940 to 1955. We found no significant difference in relative fitness between hatchery and natural fish, probably because the natural population consists largely of fish produced from the hatchery a generation or two previously. There has been a long-term trend for adults to return to the stream earlier in the spawning season. We estimated standardized selection differentials on run timing, with results indicating stabilizing selection with an optimum run timing later than the mean contemporary run timing but earlier than the historical mean run timing.

On ajoute couramment des poissons élevés artificiellement en pisciculture aux populations naturelles de poissons. En évaluant ces ajouts, il est important de mesurer la fitness relative tant des poissons de pisciculture que des poissons élevés en nature lorsqu'ils fraient ensemble dans le milieu et de déterminer comment la fitness absolue de la population naturelle change après plusieurs générations de ces ajouts. Nous évaluons la fitness relative de saumons coho (Oncorhynchus kisutch) élevés en pisciculture et en nature à Minter Creek, Washington, É.-U. Nous déterminons aussi les changements à long terme de la production naturelle de saumoneaux dans ce cours d'eau après plusieurs décennies d'ajouts importants de poissons de pisciculture. Nous estimons la production totale de saumoneaux à respectivement 14 660 et 19 415 en 2002 et 2003, alors que le nombre moyen était de 28 425 de 1940 à 1955. Nous ne trouvons aucune différence significative de fitness relative entre les poissons de pisciculture et les poissons sauvages, probablement parce que la population naturelle est composée en grande partie de poissons produits en pisciculture il y a une ou deux générations. Il y a chez les poissons une tendance à long terme à retourner au cours d'eau plus tôt dans la saison de fraie. Nous estimons les différentiels standardisés de sélection dans le calendrier de la montaison qui indiquent l'existence d'une sélection stabilisante; la montaison optimale se situe plus tard que la montaison actuelle, mais plus tôt que la période moyenne de montaison dans le passé.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2006-10-01

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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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