Late-season mortality during migration of radio-tagged adult sockeye salmon (Oncorhynchus nerka) in the Columbia River

Abstract

We radio-tagged 577 adult sockeye salmon (Oncorhynchus nerka) returning to the Columbia River in 1997 to determine how migration behaviors were related to migration success in an altered river system. The probability of successful migration declined dramatically for late-entry individuals, concomitant with declines in discharge and the onset of stressful temperatures. Long dam passage times were not related to unsuccessful migration at most dams. However, when migration histories were analyzed across multiple dams or reservoirs, relatively slow migration was significantly associated with unsuccessful migration, suggesting potential cumulative effects. Median passage times at dams were rapid (7.9-33.4 h), although 0.2%-8% of salmon took more than 5 days to pass. Reservoir passage was also rapid, averaging 36.8-61.3 km·day -1 , and appeared to compensate for slowed migration at dams. Rates observed in the unimpounded Hanford Reach suggest that total predam migration rates may have been similar to current rates. Overall, our results suggest that cumulative effects may be more important than negative effects of passage at single dams and that hydrosystem alteration of temperature regimes in the migration corridor may have an important indirect negative impact on adults.Résumé : Nous avons muni d'émetteurs radio 577 saumons rouges (Oncorhynchus nerka) qui retournaient dans le Columbia, afin de déterminer de quelle manière les comportements migrateurs sont reliés au succès de la migration dans un système hydrographique modifié. La probabilité d'une migration réussie diminue de façon spectaculaire chez les individus qui arrivent tard, au moment où le débit diminue et où les températures accablantes s'installent. Dans la plupart des barrages, la durée prolongée de traversée n'est pas reliée à l'insuccès de la migration. Cependant, lorsque le parcours de la migration au travers plusieurs barrages et réservoirs est analysé, il y a une relation significative entre une migration relativement lente et l'insuccès de la migration, ce qui indique la possibilité d'effets cumulatifs. La durée médiane du passage des barrages est courte (7,9-33,4 h), bien que 0,2-8 % des poissons mettent plus de 5 jours à les traverser. La traversée des réservoirs est aussi rapide, à une vitesse moyenne de 36,8-61,3 km·jour -1 , et semble compenser le ralentissement de la migration aux barrages. Les taux observés dans la section Hanford qui ne contient pas de réservoir indiquent que les taux de migration avant l'érection des barrages ont dû être semblables aux taux actuels. En gros, nos résultats indiquent que les effets cumulatifs peuvent être plus importants que les effets négatifs causés par le passage des barrages individuels et que la modification des régimes thermiques du système hydrographique dans le corridor de migration peut avoir un important impact négatif indirect sur les adultes.[Traduit par la Rédaction] Naughton et al. 47

Behavioral Thermoregulation and Slowed Migration by Adult Fall Chinook Salmon in Response to High Columbia River Water Temperatures

“…However, the fact that median dates have remained relatively unchanged suggests that, on average, this run has probably been exposed to increasingly warmer water temperatures over time. The implications of this for survival, energetic demands, and gamete development are unclear, though exposure to high temperatures during migration has been associated with elevated bioenergetic depletion and prespawn mortality (Gilhousen 1990;Cooke et al 2004;Naughton et al 2005;Richter and Kolmes 2005) and lowered fertility (Flett et al 1996;King et al 2003) in other salmon runs.…”

The impact of a small-scale riverine obstacle on the upstream migration of Atlantic Salmon

“…A number of studies have shown successful migrants (i.e. individuals which reached spawning grounds) had lower approach and passage times at obstacles when compared with unsuccessful individuals Naughton et al, 2005;Lundqvist et al, 2008;Makiguchi et al, 2011), suggesting potentially rapid obstacle passage reduces energetic costs in barrier passage resulting in greater success of reproduction.…”

A Comparison of the Physiological Condition, and Fishway Passage Time and Success of Migrant Adult Sockeye Salmon at Seton River Dam, British Columbia, under Three Operational Water Discharge Rates

“…Passage time at dams along the Columbia and Snake rivers have been strongly related to time of day as migrant salmon have been observed to overnight in the tailrace prior to passage (Naughton et al 2005;Caudill et al 2007). However, this did not appear to explain the difference in passage times we observed at Seton Dam as there was no difference in release times among the three discharge periods.…”

“…Because time of day can affect passage rates at dams (Naughton et al 2005), we compared release times of tagged fish among the discharge periods using a Wilcoxon-Kruskal-Wallis test, and conducted a Spearman's rank correlation analysis between release time of day and passage time. Passage times, which were normally distributed under each discharge period (Kolmogorov-Smirnov test; all P .…”

“…The spawning migrations of Pacific salmon are one of the most physically challenging stages of their lives , and many populations must pass dams en route to spawning grounds (up to nine separate dams in some cases; Naughton et al 2005). During dam passage events, fish exposed to high tailrace water velocities may accrue physiological stress if they are forced to swim with anaerobic efforts.…”