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Physiology of individual late-run Fraser River sockeye salmon (Oncorhynchus nerka) sampled in the ocean correlates with fate during spawning migration

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Beginning in 1995, segments of the late-run sockeye salmon (Oncorhynchus nerka) stocks from the Fraser River, British Columbia, have initiated upriver spawning migration up to 6 weeks earlier than historical records; and those fish have experienced high rates of en route mortality. We examined the correlations between physiological and energetic status prior to river entry with subsequent migratory performance of individual salmon using telemetry and noninvasive biopsies for Adams–Thompson–Shuswap (Adams) and Weaver–Harrison (W–H) stocks. Salmon that failed to reach the river were characterized by a tendency to have elevated levels of chronic and acute stress indicators. For one stock of fish (i.e., Adams) that entered the river, those that died before reaching spawning grounds were individuals with low gross somatic energy. Furthermore, females tended to have elevated plasma estradiol levels. When contrasting fish with different behaviours and fates, fish that did not hold in the estuary and subsequently died tended to have less energy than fish that held and reached spawning areas. Females from the former group also had higher 11-ketotestosterone and estradiol levels relative to those from the later group. These data suggest that differences in physiological and energetic status may be associated with high en route mortality in late-run sockeye salmon.

Depuis 1995, des portions des stocks à migration tardive de saumons rouges (Oncorhynchus nerka) du Fraser, Colombie-Britannique, commencent leur migration de reproduction vers l'amont jusqu'à six semaines avant la période normale du passé et elles subissent de forts taux de mortalité durant le trajet. Nous examinons les corrélations entre les statuts physiologique et énergétique avant l'entrée en rivière et la performance subséquente de la migration chez des saumons individuels des stocks Adams–Thompson–Shuswap (Adams) et Weaver–Harrison (W–H) à l'aide de la télémétrie et de biopsies non invasives. Les saumons qui n'atteignent pas la rivière ont tendance à avoir des niveaux élevés d'indicateurs de stress chronique et aigu. Chez l'un des stocks (c.-à-d., Adams) qui a pénétré dans la rivière, les poissons qui sont morts avant d'atteindre les sites de fraye étaient des individus possédant une faible énergie somatique brute. De plus, les femelles avaient tendance à avoir des concentrations plasmatiques élevées d'oestradiol. En comparant des poissons ayant des comportements et des sorts différents, nous trouvons que les poissons qui ne se sont pas maintenus dans l'estuaire et qui sont morts subséquemment avaient tendance à avoir moins d'énergie que les poissons qui se sont maintenus et qui ont atteint les sites de fraye; les femelles du premier groupe avaient aussi des concentrations plus élevées de 11-céto-testostérone et d'oestradiol que celles du second groupe. Ces données indiquent que les statuts physiologique et énergétique peuvent être associés à une forte mortalité durant le trajet chez le saumon rouge.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: July 1, 2006

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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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