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Estimated Dam Passage Survival Parameter Values
Draft Biological Opinion, Appendix B
Data Reformatted from Tables B-1 through B-6

National Marine Fisheries Service, July 27, 2000

  Current Estimate Estimate of Future
Dam Spring/Summer
Steelhead Spring/Summer
Lower Granite Turbine 93% 90% 93% 93% 90% 93%
Little Goose Turbine 92% 90% 92% 92% 90% 93%
Lower Monumental Turbine 92% 90% 93% 92% 90% 93%
Ice Harbor Turbine 90% 90% 90% 90% 90% 90%
McNary Turbine 90% 90% 90% 90% 90% 90%
John Day Turbine 90% 90% 90% 90% 90% 90%
The Dalles Turbine 90% 90% 90% 92% 92% 92%
Bonneville I Turbine 90% 90% 90% 92% 92% 92%
Bonneville II Turbine 90% 94% 90% 90% 94% 90%
Lower Granite Spillway 98% 98% 98% 98% 98% 98%
Little Goose Spillway 100% 98% 100% 100% 98% 100%
Lower Monumental Spillway 97% 98% 97% 98% 98% 99%
Ice Harbor Spillway 98% 98% 98% 98% 98% 98%
McNary Spillway 98% 98% 98% 98% 98% 98%
John Day Spillway 98% 98% 98% 98% 98% 98%
The Dalles Spillway 90% 88% 90% 98% 98% 98%
Bonneville Spillway 98% 98% 98% 98% 98% 98%
Lower Granite Bypass 98% 98%1 98% 99% 99% 99%
Little Goose Bypass 99% 98%1 95% 99% 98% 98%
Lower Monumental Bypass 95% 98%1 93% 99% 98% 99%
Ice Harbor Bypass 98% 98%1 98% 98% 98% 98%
McNary Bypass 98% 97%1 98% 99% 99% 99%
John Day Bypass 98% 98%1 98% 98% 98% 98%
The Dalles SBC or Sluice 96% 89% 96% 98% 96% 98%
Bonneville I Bypass 90% 82% 90% 98% 98% 98%
Bonneville II Bypass 98% 98%1 98% 98% 98% 98%
Lower Granite Pool 94.2% 59.9% 90.9%  
Little Goose Pool 92.8% 80.4% 93.4%  
Lower Monumental Pool 95.4% 85.5% 95.8%  
Ice Harbor Pool 93.6% 85.1% 92.7%  
McNary Pool 92.9% 80.4% 91.8%  
John Day Pool 85.0% 64.3% 86.9%  
The Dalles Pool 96.0% 88.7% 95.9%  
Bonneville Pool 78.9% 92.4% 90.5%  
FCRPS System Survival 39.2% 7.9% 37.1% Eight Dams & Pools
Dam Spring/Summer
Steelhead Spring/Summer
  Current Estimate Estimate of Future

Bold indicates an expected improvement from "Recommended and Prudent Alternatives"
Bold in blue indicates an expected improvement greater than 1%

See also this data in another format at Survival of Downstream Migration

In 1997 and 1998, Caspian terns nesting on Rice Island consumed between 6 million and 25 million, and 7 million and 15 million smolts (6-25 percent and 8-16 percent, respectively, of the estimated number of salmonid smolts to reach the estuary). Among those fish are 12 salmon and steelhead stocks listed under the Endangered Species Act.

Idaho Fish & Game estimates about 15 of 100 spring/summer chinook entering estuary are eaten by Caspian terns but adds that many of these are the weaker fish that are likely to die before returning to spawn as adults.

See Researchers Tally Tern Relocation Impacts on Salmon

A 1992 study calclulated that during the 100 days when adult Snake River spring chinook were migrating, 2,100 seals in the Columbia River consumed 15,700 salmon, of which 3,000 were Snake River chinook. A 1993 study estimated that harbor seals took 22,558 salmon of which 4,500 were assumed to be Snake River chinook.

Scarring (tooth marks and claw rakes) is considered another indicator of pinniped predation pressure on salmonids. Studies conducted in 1990 at the Lower Granite Dam with 19% of examined Snake River spring chinook showing scarring,k 1990 to 1993 showed 7.8% of the steelhead with scars and 16.4% of the spring/summer chinook. 1994 Bonneville Dam and several hatcheries on the Columbia and Snake Rivers found 24% of the steelhead with scarring and 16% of the spring chinook. Research suggests that pinniped-induced stress from scarring and injuries may also result in lowered spawning success and that considerable salmonid mortality, bot direct and indirect, may result from confrontations with, and injuries from pinnipeds.

Current harvest rates of Snake River spring/summer chinook range from 6-9% in lower river fisheries and less than 2% in ocean fisheries.

Current harvest rates remain high for listed Snake River fall chinook in downriver and ocean non-tribal and tribal fisheries. This is a signficant conservation concern. Harvest rates in ocean and lower river fisheries are approximately 40%-60% each.

These high rates, relative to spring/summer chinook, occur because listed fall chinook are intermingled with more abundant unlisted fall chinook stocks targeted by fisheries. These mixed-stock fisheries have been slow to embrace opportunities for selective fishing techniques, which would target the abundant stocks while allowing higher escapement of listed fish.

Following the listing of Snake River steelhead in 1998, NMFS established a 17% ceiling on harvest of listed B-run steelhead in mainstem Columbia River fisheries (15% tribal; 2% non-tribal). This rate is significantly higher than the harvest rate of listed spring/summer chinook, and represents an opportunity for additional conservation benefits. Current harvest rate of listed A-run steelhead in lower river fisheries is approximately 7-8%. Snake River steelhead are rarely taken in ocean fisheries.

Harvest rates for commercial fisheries on wild fish remain excessive. The Plan states that last year's harvest rate on Snake River fall chinook was about 31 percent. However, this accounts only for fisheries within the Columbia River. When ocean fisheries are added, the cumulative harvest rate rises to roughly 50 percent.

See Idaho Response to Draft 2000 FCRPS BiOp

1Survival estimates for Fall Chinook at "Medium Flows" are shown here although estimates for "High and Low Flows" are given in Table B-2.

2No Data is available for mortality/survivability before dams were built but it was certainly much less than the current mortality.

Best professional judgement was used to develop some of the passage parameters, e.g., in some cases, fish passage data gathered at one dam during a single passage season was applied to several other similar hydrosystem projects.

Reach survival data is limited to NMFS PIT tag data collected during 1994-99. These years represent a range in flow and environmental conditions. In several years, reach survival data were extrapolated from some of the upper projects in the Snake River (on a per-mile basis) to the entire system. The reach survival estimates are point estimates roughly classified by the volume of runoff during the year in which the data were collected.

Although there may be uncertainty about the accuracy of the resulting pool and dam survival estimates, the BET and NMFS found that the model output for the years 1994-99 was reasonable and produced reach survival estimates similar to the empirical estimates. Once the model was calibrated to data for the current operation, the BET and NMFS considered it had a reasonable base case from which to make comparisons of additional model studies over a range of water conditions represented by water years 1994-99 of potential future juvenile fish passage actions.

Caveats of methodology:

Related Links:
Columbia Basin Salmon Recovery Strategy

National Marine Fisheries Service (NMFS)
Survival of Downstream Migration, Compiled from Tables B-1 through B-6, Appendix B
Draft Biological Opinion, July 27, 2000

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