Temporal variation in synchrony among chinook salmon (Oncorhynchus tshawytscha) redd counts from a wilderness area in central Idaho

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Abstract:

Metapopulation dynamics have emerged as a key consideration in conservation planning for salmonid fishes. Implicit to many models of spatially structured populations is a degree of synchrony, or correlation, among populations. We used a spatially and temporally extensive database of chinook salmon (Oncorhynchus tshawytscha) redd counts from a wilderness area in central Idaho to examine patterns in synchrony as these fish underwent a sixfold decrease in abundance. Our results suggested that populations became strongly synchronous as abundances decreased and that the range, or diversity of correlations, exhibited among populations also decreased. These changes indicate that the likelihood of simultaneous extirpations has increased, which could have long-term detrimental consequences for metapopulation persistence. Implications for management are that the resilience of many metapopulations to large-scale disturbance and anthropogenic suppression may not depend solely on attempts to maintain large and productive component populations, but also on efforts to desynchronize populations that have become strongly correlated. Such efforts could entail promoting the existence of a broad distribution and diversity of habitats that support a wide array of life-history forms and ensuring that some habitats are sufficiently spatially disjunct so that risks from catastrophic stochastic events are minimized.

La dynamique des métapopulations est devenue un élément primordial de la planification de la conservation des poissons salmonidés. Plusieurs des modèles de population à structure spatiale supposent l'existence d'un degré de synchronisation ou de corrélation entre les populations. Une importante banque de données, tant spatiales que temporelles, de dénombrements de saumons quinnat (Oncorhynchus tshawytscha) sur les frayères dans une région sauvage du centre de l'Idaho nous a permis d'examiner la synchronisation au moment où ces poissons subissaient un déclin de leur abondance par un facteur de 6. Nos résultats montrent que les populations se synchronisent fortement à mesure que leur abondance diminue et que l'étendue ou la diversité des corrélations entre les populations décroît aussi. Ces changements indiquent un accroissement de la vraisemblance d'une extirpation simultanée, ce qui pourrait avoir des conséquences néfastes sur la survie de la métapopulation. Il y a aussi des implications pour la gestion : la résilience de plusieurs métapopulations aux bouleversements à grande échelle et à l'extermination par l'activité humaine peut ne pas dépendre uniquement d'efforts pour maintenir des populations constitutives importantes et productives, mais aussi d'efforts pour désynchroniser les populations qui sont en forte corrélation. On pourrait penser au développement d'une large répartition et diversité d'habitats où prévaudrait une gamme étendue de types de cycles biologiques et à la précaution que certains habitats soient suffisant éloignés les uns des autres pour que les risques engendrés par des événements catastrophiques stochastiques soient minimisés.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: July 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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