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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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Comparison of 2006 Dworshak (Snake River) Spring Chinook Smolt Survival Estimates Using Acoustic Tags Measured with the POST Array with Published Data Using PIT tagsAccoustic array data are shown as means ± 1 standard error (SE). The PIT tag data are from Tables 19 and 41 of [21]. The last two PIT tag data points are an aggregate of all Snake River spring Chinook tagged in the Snake River Basin. Regression estimates of the decline in survival with distance are statistically indistinguishable for Dworshak Hatchery smolts tagged with either PIT tags (diamonds) or acoustic tags (triangles) (p > 0.05), and are consistent with a single constant mortality rate above and below the hydropower system.
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pbio-0060265-g002: Comparison of 2006 Dworshak (Snake River) Spring Chinook Smolt Survival Estimates Using Acoustic Tags Measured with the POST Array with Published Data Using PIT tagsAccoustic array data are shown as means ± 1 standard error (SE). The PIT tag data are from Tables 19 and 41 of [21]. The last two PIT tag data points are an aggregate of all Snake River spring Chinook tagged in the Snake River Basin. Regression estimates of the decline in survival with distance are statistically indistinguishable for Dworshak Hatchery smolts tagged with either PIT tags (diamonds) or acoustic tags (triangles) (p > 0.05), and are consistent with a single constant mortality rate above and below the hydropower system.

Mentions: We first compared survival of PIT and acoustically tagged smolts in the impounded section of the Snake and Columbia rivers to assess survival of animals implanted with these different-sized tags in 2006 (Figure 2; [21]). Survival of acoustically tagged Snake River spring Chinook smolts from the Dworshak Hatchery stock (tagged and released at Kooskia Hatchery) was statistically indistinguishable from the estimated survival of PIT-tagged Dworshak Hatchery Chinook in 2006 (p > 0.05), demonstrating that the PIT and acoustic tag methodologies provide similar survival estimates for freely migrating smolts in the impounded section of the river. Of note, the decline in smolt survival with distance, evident for the POST data, suggests that a simple model of a constant freshwater mortality rate in the Columbia may be appropriate, irrespective of location in the river. However, we can not rule out the possibility that the decline in survival with distance may be punctuated, rather than smooth, at finer spatial scales not resolved by the current POST array.


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)

Comparison of 2006 Dworshak (Snake River) Spring Chinook Smolt Survival Estimates Using Acoustic Tags Measured with the POST Array with Published Data Using PIT tagsAccoustic array data are shown as means ± 1 standard error (SE). The PIT tag data are from Tables 19 and 41 of [21]. The last two PIT tag data points are an aggregate of all Snake River spring Chinook tagged in the Snake River Basin. Regression estimates of the decline in survival with distance are statistically indistinguishable for Dworshak Hatchery smolts tagged with either PIT tags (diamonds) or acoustic tags (triangles) (p > 0.05), and are consistent with a single constant mortality rate above and below the hydropower system.
© Copyright Policy
Related In: Results  -  Collection

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

pbio-0060265-g002: Comparison of 2006 Dworshak (Snake River) Spring Chinook Smolt Survival Estimates Using Acoustic Tags Measured with the POST Array with Published Data Using PIT tagsAccoustic array data are shown as means ± 1 standard error (SE). The PIT tag data are from Tables 19 and 41 of [21]. The last two PIT tag data points are an aggregate of all Snake River spring Chinook tagged in the Snake River Basin. Regression estimates of the decline in survival with distance are statistically indistinguishable for Dworshak Hatchery smolts tagged with either PIT tags (diamonds) or acoustic tags (triangles) (p > 0.05), and are consistent with a single constant mortality rate above and below the hydropower system.
Mentions: We first compared survival of PIT and acoustically tagged smolts in the impounded section of the Snake and Columbia rivers to assess survival of animals implanted with these different-sized tags in 2006 (Figure 2; [21]). Survival of acoustically tagged Snake River spring Chinook smolts from the Dworshak Hatchery stock (tagged and released at Kooskia Hatchery) was statistically indistinguishable from the estimated survival of PIT-tagged Dworshak Hatchery Chinook in 2006 (p > 0.05), demonstrating that the PIT and acoustic tag methodologies provide similar survival estimates for freely migrating smolts in the impounded section of the river. Of note, the decline in smolt survival with distance, evident for the POST data, suggests that a simple model of a constant freshwater mortality rate in the Columbia may be appropriate, irrespective of location in the river. However, we can not rule out the possibility that the decline in survival with distance may be punctuated, rather than smooth, at finer spatial scales not resolved by the current POST array.

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