more than 300 threatened chum salmon still hanging out in spawning areas
downstream of Bonneville Dam, the interagency Technical Management Team this
week put off a decision on whether to transition from the chum spawning
operations that began early last month to incubation flows.
most recent surveys by Washington Department of Fish and Wildlife biologists of
Bonneville spawning areas found 322 of the fish near Ives/Pierce island complex
on Dec. 4, and 61 chum at Horsetail, 5 at Marker 85, 120 at Multnomah Falls and
5 at St. Cloud, all on Nov. 28. Some 126 chum have passed over Bonneville Dam
as of Dec. 11.
maps of chum spawning areas at http://pweb.crohms.org/tmt/agendas/2018/0117_Ives_Island_Spawning_Areas_2017.pdf)
chum, listed as threatened under the federal Endangered Species Act, arrived
early this year and chum operations to protect the fish and their redds (nests)
began Nov. 2, about a week earlier than normal. Operations for the chum go on
for about five months, but generally transitions in late-December from spawning
to chum incubation flows.
this week of December we think about ending (spawning) chum flows,” said Tony
Norris of the Bonneville Power Administration during the TMT meeting Wednesday,
Dec. 12. “But we’re still seeing about 300 live chum and some ‘green’ fish in
TMT could decide next week as early as Tuesday whether it’s time to transition
to incubation flows, which are designed to protect the redds through
incubation. Last year that operation called for an 11.8 foot minimum tailwater
elevation at the dam at all hours for as long as up to April 10, 2018, or
flows will end automatically Dec. 31 if TMT doesn’t purposely make the
transition earlier, said BPA’s Scott Bettin.
chum operations ensure that enough water will flow over chum redds to protect
the redds and fertilized eggs until they emerge in spring. Initial spawning
operations seek flows high enough to protect chum as they build their redds,
but not so high that chum would have been encouraged to spawn in areas that
could be dewatered when flows drop.
operations maintain the dam’s tailwater elevation at a minimum 11.3 feet so
that the fish can move into spawning areas near Hamilton Creek and Ives Island.
a special operation was adopted by the U.S. Army Corps of Engineers, with the
approval of WDFW, Dec. 7 when down power at the Columbia Generation
Station required the Corps to move an additional amount of water through the
system, according to a memo from the Corps’ Doug Baus.
to generally dry conditions we are making a small adjustment to the chum
operation to minimize the risk of chum spawning at higher elevations while this
water moves through the system,” the memo says.
do that, the Corps narrowed the daytime tailwater elevation from 11.3 to 13.0
feet down to 11.3 to 12.0 feet in order to keep the daytime tailwater below
elevation 12.0 feet and move any additional water at night.
situation eased by Tuesday, Dec. 11, and chum operations returned to a 24-hour
tailwater elevation of 11.3 to 13 feet, Baus said.
said that precipitation in the basin has generally been below normal: 81
percent of normal in the Snake and Clearwater river basins and 78 percent of
normal above The Dalles Dam.
rainfall has been skimpy in the Columbia River basin, water flow will remain
sufficient to maintain the chum operations, at least for the next 10 days. The
short-term weather (5-day) forecast includes some but not a lot of
precipitation, the longer 10-day forecast looks better. “The good news,” Baus
said, “is that we’re finally getting some precipitation to the basin.”
at Bonneville are currently at about 128,000 cubic feet per second and that is
expected to change slightly with a 10-day flow forecast of 128 kcfs to 140 kcfs
(see NOAA’s River Forecast Center at https://www.nwrfc.noaa.gov/river/station/flowplot/flowplot.cgi?id=BONO3).
CBB, November 2, 2018, “ESA-Listed Chum Salmon Arrive Early Below Bonneville
Dam; Flow Operations Begin To Protect Spawning,”
January 19, 2018, “Agencies Identify Spawning Areas For Chum, Confirm Safe
Water Levels Over Redds,” http://www.cbbulletin.com/440103.aspx.