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River Ops Review 2017: Overall Hydrosystem Survival for
Chinook/Steelhead Smolts Below Average

by Staff
Columbia Basin Bulletin, December 22, 2017

Estimated Survival Probability for Snake River Chinook and Steelhead. For the third straight year, overall hydrosystem survival -- Lower Granite Dam on the lower Snake River to Bonneville Dam on the lower Columbia River -- for yearling chinook smolts during spring 2017 was below average (this year about 6 percent below average), with an overall survival rate of 44 percent, according to a preliminary report.

And the deficit is in the lower Columbia River, said Steve Smith of NOAA Fisheries, as he described preliminary data for smolt survival, travel time down through the dams and the percentage of smolts transported by barges at the Technical Management Team's Year End Review, Dec. 12, in Portland.

TMT is made up of fisheries and hydro/reservoir managers from state, federal and tribal agencies. Every December the group looks back at actions taken during spring and summer in managing Columbia and Snake river federal hydro/fish operations. Smith's presentation was among nine reviewed in the day-long session. Go to to see all presentations.

With spring's higher flows and more spill, yearling chinook were swept down river and the median amount of time it took for the fish to complete their initial migration journey -- Lower Granite to Bonneville -- was faster than in all years since 2001, although still very similar to 2016's travel time. In early April travel time was about 17 days, but by May it took the fish only about 10 days to make the journey and in early June the timing of the journey dropped to about 7 days.

Travel time during 2015's low flows was a good four to five days slower, Smith said.

Steelhead move much faster than chinook and "for most of 2017 these were the fastest moving steelhead that we've seen," he said. The steelhead journey over most the study time -- early April through mid-June -- was under 10 days, dropping to a low of 7 days June 4.

Reach by reach survival varied: survival of yearling chinook from Snake and Clearwater river hatcheries to Lower Granite Dam was 65 percent, which is near the mean of 64.8 days. Survival from upper Columbia River hatcheries to McNary Dam was slightly above average at 58.2 percent (the mean since 1999 is 56.5 percent).

Upper Columbia River steelhead survival to McNary Dam this year was 43.7 percent, slightly higher than the mean since 1999 of 41.9 percent.

All reaches (dam to dam) had above average survival with the exceptions of McNary Dam to John Day Dam where survival for yearling chinook was just 72 percent (mean survival is 87.2 percent), Little Goose Dam to Lower Monumental Dam where survival was 90.8 percent (mean survival is 94 percent) and Lower Granite to Little Goose where survival was 91.6 percent (mean is 93.3 percent).

Overall survival of Snake River yearling chinook from Lower Granite to McNary in 2017 was 74.3 percent, slightly lower than the mean of 75.5 percent.

Overall survival from McNary to Bonneville was 64.3 percent, far lower than the mean of 71.6 percent.

Survival for upper Columbia yearling chinook was vastly different with a survival of fish from McNary to Bonneville of 94.4 percent. The mean is 82.5 percent.

Snake River steelhead survival was below the mean at lower Columbia dams. The Dalles Dam to Bonneville survival this year was 80.2 percent (mean survival is 89.1 percent). John Day to Bonneville survival was 64.3 percent (mean is 80 percent). However, McNary to John Day survival was 94.1 percent, higher than the mean of 85.7 percent.

Survival for steelhead in Snake River reaches was higher than the mean at all four dams. Lower Granite to McNary survival was 75.9 percent, higher than the mean of 67.4 percent.

However, McNary to Bonneville survival for steelhead was 60.5 percent, far lower than the mean of 70.8 percent.

As with yearling chinook, survival of steelhead from the upper Columbia was much better than average. Survival this year was 96.4 percent, whereas the mean is 74.7 percent.

The entire journey -- the Snake River trap upstream of Lower Granite Dam to Bonneville -- for yearling chinook this year was below the mean survival with 44.4 percent survival compared to the mean of 50.5 percent.

For steelhead for the same long stretch of Snake and Columbia rivers, survival was 42.9 percent while the mean is 48.9 percent.

Survival of Springfield Hatchery Snake River sockeye from the Redfish Lake Trap to Lower Granite Dam was a dismal 16.2 percent. The mean is 46 percent. Snake River sockeye are listed as endangered under the federal Endangered Species Act.

For the sockeye that made it to Lower Granite, survival was a bit better during the remainder of their journey. Lower Granite to McNary survival was 54.4 percent, but still much lower than the mean at 66.4 percent. McNary to Bonneville survival was just 32.4 percent, while the mean since 1997 is nearly twice as high at 61.2 percent.

Overall survival of sockeye -- Lower Granite to Bonneville -- was a nearly record low of 17.6 percent. The mean since 1997 is 44.2 percent.

The number of smolts transported this year was low, continuing a trend of fewer and fewer Snake River fish traveling by barge to Bonneville Dam.

Just 19.7 percent of yearling chinook were transported from one of the three dams on the Snake River that collect and transport fish. 2016 was about the same, whereas transportation during the low flow year of 2015 was only about 12 percent. For the years 2007 through 2017 the mean transportation percentage is 29.7. For the years 1996 through 2005, the mean is 80.7 percent of the fish transported.

Likewise, steelhead transportation was low this year. Some 22.1 percent of the fish were transported. A slightly higher percentage of steelhead were transported in 2016 and 2015 was about 12 percent. The mean -- 2007 to 2017 -- is 33.5 percent. The mean -- 1996 to 2005 -- is 87.4 percent.

Related Sites:
2017 Juvenile Salmon/Steelhead Survival In Snake/Columbia: Fish Take Hit In McNary To John Day Reach by Staff, Columbia Basin Bulletin 10/6/17
Year-End Assessment Matches 2016 Water Supply, Stream Flow, Fish Conditions With Juvenile Migration by Staff, Columbia Basin Bulletin 10/22/16
Report Details 2016 Juvenile Salmon/Steelhead Survival In Snake/Columbia; Snake Sockeye Take A Hit by Staff, Columbia Basin Bulletin 10/7/16

River Ops Review 2017: Overall Hydrosystem Survival for Chinook/Steelhead Smolts Below Average
Columbia Basin Bulletin, December 22, 2017

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