Relationship between natural productivity and the frequency of wild fish in mixed spawning populations of wild and hatchery steelhead (Oncorhynchus mykiss)

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Abstract:

The proportion of wild fish in 12 mixed populations of hatchery and wild steelhead (Oncorhynchus mykiss) was evaluated for its relationship to mean and intrinsic measures of population productivity. The population mean of ln(recruits/spawner) was used to represent mean productivity. Intrinsic productivity was represented by values for the Ricker a parameter as estimated from fits of spawner and recruit data. Significant regressions (p < 0.001) were found between both measures of productivity and the proportion of wild fish in the spawning population (Pw). The slopes of the two regressions were not significantly different (p = 0.55) and defined a relationship suggesting that a spawning population comprised of equal numbers of hatchery and wild fish would produce 63% fewer recruits per spawner than one comprised entirely of wild fish. Study findings were not sensitive to likely levels of data error or confounded by extraneous habitat correlation with Pw. Population status assessments and conservation monitoring efforts should include Pw as a critical variable. For natural populations, removal rather than addition of hatchery fish may be the most effective strategy to improve productivity and resilience.

La proportion de poissons sauvages dans 12 populations mixtes de truites arc-en-ciel anadromes (Oncorhynchus mykiss) sauvages et de pisciculture a été mise en relation avec des mesures de productivité moyenne et intrinsèque de la population. La moyenne de ln(recrues–reproducteurs) dans la population représente la productivité moyenne et les valeurs du paramètre a de Ricker calculées à partir d'ajustements des données sur les recrues et les reproducteurs, la productivité intrinsèque. Il existe des régressions significatives (p < 0,001) entre chacune des deux mesures de productivité et la proportion de poissons sauvages dans la population des reproducteurs (Pw). Les pentes des deux régressions ne diffèrent pas significativement (p = 0,55); la relation obtenue indique qu'une population de reproducteurs composée d'un nombre égal de truites sauvages et de truites de pisciculture produirait 63 % moins de recrues par reproducteur qu'une population composée entièrement de poissons sauvages. Les résultats de l'étude ne sont pas affectés par les niveaux probables des erreurs de données, ni par les corrélations accessoires entre l'habitat et Pw. Les évaluations du statut des populations et les efforts de surveillance des activités de conservation devraient donc utiliser Pw comme variable critique. Le retrait, plutôt que l'addition, de poissons de pisciculture est peut-être la stratégie la plus efficace pour augmenter la productivité et la résilience des populations naturelles.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2003

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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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