The JC Boyle Dam in Klamath County, Ore., is one
of four slated to be removed from the Klamath River under a
Memorandum of Understanding between the Klamath County
Commission and the Klamath River Renewal Corp.
report from the Bureau of Reclamation over flushing out C.
shasta spores in the Klamath River does not look promising,
but it is also early in the data analysis, experts say.
Megan Skinner, Klamath River Manager for Reclamation, the
number of spores actually spiked three or four weeks after
the river flushing was completed earlier this spring.
the preliminary results to the Klamath Irrigation District
board members last week. Board members were taken by
surprise, as were the scientists on the ground who are
studying the river.
However, it is
not that the flushing flows are not working.
preliminary hypothesis is that adult salmon were infected
last year when they migrated up the river to spawn,” Skinner
told the KID board.
“When they died
after spawning, they released spores that were taken up by
polychaete worms (infection rates in polychaetes prior the
flushing flow were notably high this year). Polychaetes that
survived the flushing flow then released spores this spring
that infected juvenile salmon. The spores can and do result
in salmon mortality.”
In the most
recent sample, 83 percent of sampled fish were infected with
C. Shasta, Skinner said. Of that 83 percent, 13 percent had
an infection that could likely lead to mortality.
As one may
recall, Reclamation was under court order in 2017 to flush
the river with a ballpark of 50,000 acre feet of water to
dislodge the worms that host the spores. (The spores in turn
then infect juvenile salmon, especially the ones being
release from the Iron Gate hatchery.)
Now, there is a
new 2019 Biological Opinion in effect as of April 1 that
guides the Bureau of Reclamation on its water allocation, so
the court order is moot.
Sascha Hallett, microbiology senior research associate at
Oregon State University, the purpose of the flushing flows
is to mobilize sediment and reduce polychaete worm
(invertebrate host of Ceratonova shasta) populations,
thereby reducing the numbers of hosts available to produce
the infectious stage for salmonids (salmon and trout).
sampling by Julie Alexander of OSU — before and after spring
flows — indicate a reduction in worm numbers following the
increased flow. However, the determination of whether the
number of infected worms also decreased is still in progress
(sample processing is underway). Reductions in both infected
and overall populations have been observed in previous years
following high spring flows,” Hallett told the Herald and
levels have been observed in previous years characterized by
low precipitation (low flows) and warm temperatures.
Therefore, this year because of the high precipitation, flow
events, cool winter water temperature and decrease in
polychaetes, we were anticipating a low parasite year, and
if temperature remained low, a low disease year, she said.
in the river usually increase with increasing water
temperature in spring.
is what we observed this year — waterborne parasite was not
detected until mid-spring, which is typical of a
low-moderate disease year. However, once levels began to
increase they did so surprisingly quickly — by more than an
order of magnitude from one week to the next,” Hallett said.
waterborne parasite levels are unexpectedly high post-flow
this year, and of concern, these levels might have been even
higher had the flows not occurred, Hallett noted.
“So it is too
early to know whether the flows achieved all components of
their goal,” Hallett said.
It is important
to be mindful that high parasite abundance alone does not
necessarily translate to disease and population-level
impacts on salmon – river water temperature and length of
exposure (i.e. total parasite dose) are also contributing
From Reclamation’s perspective
flow last month was done under the 2019 Biological
Opinions,” said Laura Williams, public relations for
amount of water used specifically for the flow is not
important under the new BiOp. For this flow especially, the
total water used is not important since it was done as part
of flood control operations. The water would have gone down
river because it was necessary to release it to keep the
levies surrounding Upper Klamath Lake from breaching” she
flushing flow numbers required are 6,030 cubic feet per
second for 72 hours. However, because it all happened as a
result of required flood control operations, much higher
flows happened to keep people safe, Williams noted.
In accordance with Title 17 U.S.C.
section 107, any copyrighted material
herein is distributed without profit or
payment to those who have expressed a
prior interest in receiving this
information for non-profit research and
educational purposes only. For more
information go to: