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Survival of migrating salmon smolts in large rivers with and without dams.

Welch DW, Rechisky EL, Melnychuk MC, Porter AD, Walters CJ, Clements S, Clemens BJ, McKinley RS, Schreck C - PLoS Biol. (2008)

Bottom Line: Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams.Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent.Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River.

View Article: PubMed Central - PubMed

Affiliation: Kintama Research, Nanaimo, British Columbia, Canada. david.welch@kintamaresearch.org

ABSTRACT
The mortality of salmon smolts during their migration out of freshwater and into the ocean has been difficult to measure. In the Columbia River, which has an extensive network of hydroelectric dams, the decline in abundance of adult salmon returning from the ocean since the late 1970s has been ascribed in large measure to the presence of the dams, although the completion of the hydropower system occurred at the same time as large-scale shifts in ocean climate, as measured by climate indices such as the Pacific Decadal Oscillation. We measured the survival of salmon smolts during their migration to sea using elements of the large-scale acoustic telemetry system, the Pacific Ocean Shelf Tracking (POST) array. Survival measurements using acoustic tags were comparable to those obtained independently using the Passive Integrated Transponder (PIT) tag system, which is operational at Columbia and Snake River dams. Because the technology underlying the POST array works in both freshwater and the ocean, it is therefore possible to extend the measurement of survival to large rivers lacking dams, such as the Fraser, and to also extend the measurement of survival to the lower Columbia River and estuary, where there are no dams. Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams. Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent. Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River.

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Annual Survival Estimates (%) for Thompson and Snake River Spring Chinook and Steelhead(A) Estimated survival.(B) Survival scaled per 100 kilometers traveled, S100/L.(C) Survival scaled per migration day, S1/T.For each species, the left panel shows the survival of different Thompson River stocks released to migrate down to the Fraser River mouth; the right panel shows the survival of Snake River stocks migrating down three sections of the Columbia River hydropower system: Impounded (upper river; eight dams), Unimpounded (lower river; undammed), and Entire river. The cross to the right of each group of individual survival estimates (open circles) shows the average survival and 95% confidence interval for the group, averaged across all available data (see Text S3 for details). For ease of comparison, the average Fraser River survival and 95% confidence limits are also drawn as a band across the Columbia River results. For Snake River stocks, impounded refers to survival measured using PIT tags from the Snake River trap to the last (Bonneville) dam (see Table 1). Unimpounded refers to survival measured from Bonneville Dam to near the river mouth (Astoria) using acoustic tags. The Chinook survival value for “Entire River” is based on the 2006 study using acoustically tagged Dworshak Hatchery smolts (tagged and released at Kooskia National Fish Hatchery) and whose survival was measured at an ocean listening line at Willapa Bay, 920 km distant.A single whole-river estimate is not available for steelhead, but a synthetic value can be obtained for 2002 and 2003 by multiplying up-river PIT tag survival by lower river acoustic tag survival, and scaling by total travel distance or time as appropriate. A similar combined estimate of survival for Chinook can be calculated from the 2004 data, and is also shown for comparison. In all comparisons of average river survival, Snake-Columbia River estimates were significantly different than Thompson-Fraser estimates at the 95% level unless indicated by “NS.”
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pbio-0060265-g003: Annual Survival Estimates (%) for Thompson and Snake River Spring Chinook and Steelhead(A) Estimated survival.(B) Survival scaled per 100 kilometers traveled, S100/L.(C) Survival scaled per migration day, S1/T.For each species, the left panel shows the survival of different Thompson River stocks released to migrate down to the Fraser River mouth; the right panel shows the survival of Snake River stocks migrating down three sections of the Columbia River hydropower system: Impounded (upper river; eight dams), Unimpounded (lower river; undammed), and Entire river. The cross to the right of each group of individual survival estimates (open circles) shows the average survival and 95% confidence interval for the group, averaged across all available data (see Text S3 for details). For ease of comparison, the average Fraser River survival and 95% confidence limits are also drawn as a band across the Columbia River results. For Snake River stocks, impounded refers to survival measured using PIT tags from the Snake River trap to the last (Bonneville) dam (see Table 1). Unimpounded refers to survival measured from Bonneville Dam to near the river mouth (Astoria) using acoustic tags. The Chinook survival value for “Entire River” is based on the 2006 study using acoustically tagged Dworshak Hatchery smolts (tagged and released at Kooskia National Fish Hatchery) and whose survival was measured at an ocean listening line at Willapa Bay, 920 km distant.A single whole-river estimate is not available for steelhead, but a synthetic value can be obtained for 2002 and 2003 by multiplying up-river PIT tag survival by lower river acoustic tag survival, and scaling by total travel distance or time as appropriate. A similar combined estimate of survival for Chinook can be calculated from the 2004 data, and is also shown for comparison. In all comparisons of average river survival, Snake-Columbia River estimates were significantly different than Thompson-Fraser estimates at the 95% level unless indicated by “NS.”

Mentions: Comparing survival between river systems, survival of smolts migrating the entire length of the river was either statistically indistinguishable (spring Chinook) between the undammed Thompson-Fraser River and the heavily impounded (eight dam) Snake-Columbia River system or slightly better in the Thompson-Fraser River (steelhead; Figure 3A). When considered separately by river section, survival of Snake River smolts through the eight dams comprising the impounded section of the river down to Bonneville Dam was higher (Chinook) or statistically indistinguishable (steelhead) from the survival for the entire Fraser River. For both species, survival in the free-flowing lower section of the Columbia River was higher than the entire-river estimate for the Fraser River.


Survival of migrating salmon smolts in large rivers with and without dams.

Welch DW, Rechisky EL, Melnychuk MC, Porter AD, Walters CJ, Clements S, Clemens BJ, McKinley RS, Schreck C - PLoS Biol. (2008)

Annual Survival Estimates (%) for Thompson and Snake River Spring Chinook and Steelhead(A) Estimated survival.(B) Survival scaled per 100 kilometers traveled, S100/L.(C) Survival scaled per migration day, S1/T.For each species, the left panel shows the survival of different Thompson River stocks released to migrate down to the Fraser River mouth; the right panel shows the survival of Snake River stocks migrating down three sections of the Columbia River hydropower system: Impounded (upper river; eight dams), Unimpounded (lower river; undammed), and Entire river. The cross to the right of each group of individual survival estimates (open circles) shows the average survival and 95% confidence interval for the group, averaged across all available data (see Text S3 for details). For ease of comparison, the average Fraser River survival and 95% confidence limits are also drawn as a band across the Columbia River results. For Snake River stocks, impounded refers to survival measured using PIT tags from the Snake River trap to the last (Bonneville) dam (see Table 1). Unimpounded refers to survival measured from Bonneville Dam to near the river mouth (Astoria) using acoustic tags. The Chinook survival value for “Entire River” is based on the 2006 study using acoustically tagged Dworshak Hatchery smolts (tagged and released at Kooskia National Fish Hatchery) and whose survival was measured at an ocean listening line at Willapa Bay, 920 km distant.A single whole-river estimate is not available for steelhead, but a synthetic value can be obtained for 2002 and 2003 by multiplying up-river PIT tag survival by lower river acoustic tag survival, and scaling by total travel distance or time as appropriate. A similar combined estimate of survival for Chinook can be calculated from the 2004 data, and is also shown for comparison. In all comparisons of average river survival, Snake-Columbia River estimates were significantly different than Thompson-Fraser estimates at the 95% level unless indicated by “NS.”
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2573937&req=5

pbio-0060265-g003: Annual Survival Estimates (%) for Thompson and Snake River Spring Chinook and Steelhead(A) Estimated survival.(B) Survival scaled per 100 kilometers traveled, S100/L.(C) Survival scaled per migration day, S1/T.For each species, the left panel shows the survival of different Thompson River stocks released to migrate down to the Fraser River mouth; the right panel shows the survival of Snake River stocks migrating down three sections of the Columbia River hydropower system: Impounded (upper river; eight dams), Unimpounded (lower river; undammed), and Entire river. The cross to the right of each group of individual survival estimates (open circles) shows the average survival and 95% confidence interval for the group, averaged across all available data (see Text S3 for details). For ease of comparison, the average Fraser River survival and 95% confidence limits are also drawn as a band across the Columbia River results. For Snake River stocks, impounded refers to survival measured using PIT tags from the Snake River trap to the last (Bonneville) dam (see Table 1). Unimpounded refers to survival measured from Bonneville Dam to near the river mouth (Astoria) using acoustic tags. The Chinook survival value for “Entire River” is based on the 2006 study using acoustically tagged Dworshak Hatchery smolts (tagged and released at Kooskia National Fish Hatchery) and whose survival was measured at an ocean listening line at Willapa Bay, 920 km distant.A single whole-river estimate is not available for steelhead, but a synthetic value can be obtained for 2002 and 2003 by multiplying up-river PIT tag survival by lower river acoustic tag survival, and scaling by total travel distance or time as appropriate. A similar combined estimate of survival for Chinook can be calculated from the 2004 data, and is also shown for comparison. In all comparisons of average river survival, Snake-Columbia River estimates were significantly different than Thompson-Fraser estimates at the 95% level unless indicated by “NS.”
Mentions: Comparing survival between river systems, survival of smolts migrating the entire length of the river was either statistically indistinguishable (spring Chinook) between the undammed Thompson-Fraser River and the heavily impounded (eight dam) Snake-Columbia River system or slightly better in the Thompson-Fraser River (steelhead; Figure 3A). When considered separately by river section, survival of Snake River smolts through the eight dams comprising the impounded section of the river down to Bonneville Dam was higher (Chinook) or statistically indistinguishable (steelhead) from the survival for the entire Fraser River. For both species, survival in the free-flowing lower section of the Columbia River was higher than the entire-river estimate for the Fraser River.

Bottom Line: Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams.Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent.Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River.

View Article: PubMed Central - PubMed

Affiliation: Kintama Research, Nanaimo, British Columbia, Canada. david.welch@kintamaresearch.org

ABSTRACT
The mortality of salmon smolts during their migration out of freshwater and into the ocean has been difficult to measure. In the Columbia River, which has an extensive network of hydroelectric dams, the decline in abundance of adult salmon returning from the ocean since the late 1970s has been ascribed in large measure to the presence of the dams, although the completion of the hydropower system occurred at the same time as large-scale shifts in ocean climate, as measured by climate indices such as the Pacific Decadal Oscillation. We measured the survival of salmon smolts during their migration to sea using elements of the large-scale acoustic telemetry system, the Pacific Ocean Shelf Tracking (POST) array. Survival measurements using acoustic tags were comparable to those obtained independently using the Passive Integrated Transponder (PIT) tag system, which is operational at Columbia and Snake River dams. Because the technology underlying the POST array works in both freshwater and the ocean, it is therefore possible to extend the measurement of survival to large rivers lacking dams, such as the Fraser, and to also extend the measurement of survival to the lower Columbia River and estuary, where there are no dams. Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams. Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent. Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River.

Show MeSH
Related in: MedlinePlus