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The influence of family-correlated survival on Nb/N for progeny from integrated multi- and single-generation hatchery stocks of coho salmon (Oncorhynchus kisutch)

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Abstract:

There exist surprisingly few data on the final variance and mean of family sizes for hatchery-born fish at the adult stage. Thus, it is difficult to predict, for a conservation hatchery operation that minimizes the variance in progeny number, how much lower the true effective population size (Ne) of a cohort of hatchery-born adults will be than Ne predicted simply by the number of parents that produced them. We used parentage analysis to estimate the survival and Ne for two integrated stocks of hatchery coho salmon (Oncorhynchus kisutch). One hatchery is a multigeneration stock obtained by spawning 70% hatchery with 30% naturally reproducing fish, whereas the second is a single-generation stock derived from naturally reproducing coho. There was no significant difference in average overall survival between stocks, but observed Ne was significantly less than expected for each stock. Family-correlated survival contributed to roughly a 20% reduction in Ne over the freshwater and marine life stages. This reduction is similar to previous estimates and suggests a value that can be used when estimating the effective number of hatchery parents in applications of the Ryman–Laikre formula (at least for programs such as ours that attempt to equalize sex ratios and family sizes).

Il existe étonnamment peu de données sur la variance et la moyenne finales des tailles des familles au stade adulte chez les poissons nés en pisciculture. Il est ainsi difficile, dans une pisciculture de conservation qui minimise la variance des nombres dans la progéniture, de prédire de combien inférieure sera la véritable taille effective de la population (Ne) d'une cohorte d'adultes nés en pisciculture par rapport au Ne prédit simplement par le nombre des parents qui les ont produits. Nous utilisons une analyse de parenté pour estimer la survie et le Ne chez deux stocks intégrés de saumons coho (Oncorhynchus kisutch) de pisciculture. Une des piscicultures utilise un stock de plusieurs générations obtenu en croisant 70 % de poissons de pisciculture avec 30 % de poissons à reproduction naturelle, alors que l'autre est formé d'un seul stock de saumons coho à reproduction naturelle. Il n'y a pas de différence de survie globale entre les stocks, mais le Ne observé est significativement inférieur à la valeur attendue pour chacun des stocks. La survie en fonction de la famille contribue grosso modo 20 % de la réduction de Ne au cours des stades du cycle en eau douce et en mer. Cette réduction est semblable à celle des estimations antérieures, ce qui fournit une valeur qui peut être utilisée pour calculer le nombre effectif de parents de pisciculture lors de l'application de la formule de Ryman–Laikre (au moins dans les programmes comme le nôtre qui cherchent à égaliser les rapports mâles–femelles et les tailles des familles).[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2007-09-01

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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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