time it took juvenile salmon and steelhead to travel in-river through the four
lower Snake River dams in the spring of 2018 was among the shortest recorded,
with travel times similar to the those experienced in 2017, a year when both
spill and flows were also high.
median travel time for yearling chinook traveling in-river the 461 kilometers
(286 miles) passing Lower Granite in mid-May and traveling to Bonneville was
about 10 days, slightly quicker than in 2017, and faster than the mean of about
12 days. Travel time in mid-May 2001, a low flow year, was about 20 days.
about 7 days, steelhead leaving Lower Granite Dam May 21 traveled even faster
through the eight dams in May than they did in 2017.
in 2018 spring flow and spill at the dams was higher than average (31 percent
higher for flow and slightly higher spill) and fish transportation began
earlier (some 45 percent of juveniles found their way downstream by barge), but
not all species of salmonids that were left in river survived at the same
rates, according to a presentation by Steve Smith, Fish Ecology Division,
Northwest Fisheries Science Center, NOAA Fisheries, at the Technical Management
Team’s Year End Review last month.
chinook, starting from a trap on the Snake River upstream of Lower Granite Dam
(the upstream dam of the four lower Snake River dams), survived to Bonneville Dam
at a 38.1 percent rate, far below the mean since 1997 of 49.7 percent.
Steelhead did better, with a 52.3 percent survival (mean is 49.1 percent).
River sockeye salmon, listed as endangered under the federal Endangered Species
Act, had a relatively good year in 2018, with 64.3 percent survival from Lower
Granite to Bonneville. The mean is 45.7 percent survival. However, sockeye out
of the upper Columbia had a poor year, with survival from Rock Island Dam to
Bonneville of just 34.4 percent (the mean is 47.1 percent).
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
presentation was among nine reviewed in the day-long session (see http://pweb.crohms.org/tmt/agendas/2018/1219_Smith_Smolt_Survival%20and%20Transportation%20-%202018%20TMT%20Year-End.pdf).
for yearling chinook from the trap upstream of Lower Granite Dam was about
average through the Snake River, but when the four lower Columbia River dams
are added into the mix, overall survival from the trap to Bonneville Dam was at
just 38 percent, Smith said.
juveniles survived the trip much better, with an overall survival from the trap
to Bonneville of 52 percent. Sockeye salmon juveniles also fared better with
survival through both rivers of 64 percent.
at Lower Granite Dam began to rise in late April and continued to increase
through May. The 2017 flow was somewhat higher, but declined in mid-May to
below 2018 levels before rebounding one week later. The extremely high flows of
1997 exceeded both years.
with court-ordered spill to state total dissolved gas limits, spill at Lower
Granite was just slightly higher than the mean using data that began in 2001.
additional spill to state TDG limits, known as gas caps, was mandated at lower
Columbia and Snake river dams by an April 2017 order from Judge Michael H.
Simon of the U.S. District Court of Oregon. Simon had ordered 24-hour spring
spill for one year only in 2018 beginning April 3 at lower Snake River projects
and April 10 at lower Columbia River projects, and ending June 20 on the Snake
River and June 15 on the Columbia River.
in 2018 in the Lower Granite tailrace was somewhat above the mean, but less
than 2017 and not to the levels seen in 1997.
for yearling chinook from seven Snake River hatcheries was 64.8 percent, normal
survival for the years 1994 – 2018, whereas survival for upper Columbia River
yearling chinook from hatcheries was an above normal 60.8 percent (the median
is 56.8 percent).
for upper Columbia River steelhead from hatcheries was a near normal 41.6
percent (median survival is 41.9 percent).
evaluating survival through the eight dams, the devil is in the details. Reach
survival between Snake River dams for yearling chinook was nearly normal: from
the trap to Lower Granite, survival in 2018 was 88 percent, while the mean is
93.2 percent; survival from Lower Granite to Little Goose Dam was 94.2 percent
(mean is 93.4 percent); from Little Goose to Lower Monumental, survival was
91.7 percent and the mean is 93.9 percent.
yearling chinook traverse Columbia River dams, survival as compared to the mean
drops. While the reach from Lower Monumental on the Snake to McNary Dam on the
Columbia, a reach that includes Ice Harbor Dam on the Snake, was near normal at
87.7 percent (mean is 87.3 percent), the reach from McNary to John Day Dam at
77 percent survival was far below the mean of 86.6 percent.
reach from John Day to Bonneville (which includes The Dalles Dam) was 74.3
percent (the mean is 82.2 percent). Survival in the reach from The Dalles pool
to the Bonneville pool was 86.2 percent and the mean is 90.5 percent.
survival for steelhead out of the Snake River was higher than the mean between
reaches, and maintained the level of survival through the Columbia River dams.
The reach survival of 94.8 percent from John Day to Bonneville was far above
the mean of 81 percent.
from Lower Granite to McNary for both steelhead and yearling chinook was 73.3
percent. For chinook, the mean is 75.4 percent and 67.7 percent for steelhead.
McNary to Bonneville, survival for yearling chinook was 59 percent and the mean
is 70.9 percent. For steelhead through the same reach, survival in 2018 was
72.7 percent and the mean is 70.9 percent.
chinook from the upper Columbia fared better, surviving at a 74.9 percent rate.
Still, that’s below the mean of 82 percent.
River sockeye survival from the Redfish Lake trap to Lower Granite Dam was 59.5
percent, higher than the mean of 46 percent and much higher than last year’s
survival of Springfield Hatchery fish of about 20 percent. Lower Granite to
McNary survival was 68.4 percent (mean 66.5 percent), McNary to Bonneville was
94 percent (mean 63.6 percent) and Lower Granite to Bonneville survival was
64.3 percent (mean 45.7 percent).
River sockeye from Rock Island to McNary had high survival at 92.7 percent
(mean 72.9 percent), but survival moving downstream was much lower than normal.
McNary to Bonneville survival was 56 percent (mean 64.7 percent) and survival
through the system from Rock Island to Bonneville was 34.4 percent (mean 47.1
44.8 percent (mean 31 percent) of yearling chinook were transported from one of
the collection stations at the upper three of the lower Snake River dams. In
2017, just 20 percent of yearling chinook traveled downriver by barge and in
the low flow year of 2015 about 12 percent were transported.
steelhead, 47.6 percent were transported (mean 34.6 percent). In 2017 about 22
percent were transported and about 12 percent in 2015.
Snake River sockeye, 56.1 percent (mean 43.4 percent) were transported. Last
year some 22 percent were transported and about 41 percent were transported in