Wednesday, December 1, 2004 1:43 PM
Reference Code: PR-19714
December 1 -
— Researchers at Oregon State University have
developed a molecular method to detect and
measure a salmon and trout parasite thought
partially responsible for controversial salmon
die-offs in the Klamath River.
As many as 30 to 40 percent of fish captured
in the lower Klamath River are infected with
one particular myxozoan species, Ceratomyxa
shasta, explained Jerri Bartholomew, a
researcher in OSU's Department of Microbiology
and the Center for Fish Disease Research.
Until now, researchers had no quick, easy way
to test for the parasite in water samples.
Using the organism's own DNA, this newly
developed assay can detect even 1/1000th of a
parasite spore in a water sample.
To detect Ceratomyxa shasta prior to this
breakthrough, scientists had to maintain fish
in cages along areas of the river suspected to
be infectious, then return them to the
laboratory and wait for months to see if
clinical signs appeared. There was no way to
quantify the number of infectious spores
moving through the water.
"This is a huge jump in what we're able to
do," said Bartholomew. "We wanted to offer a
tool that would be useful if managers were to
test management options like altering flows at
certain times of year, so that effects could
be determined immediately."
Natural resource managers welcome the new
"Jerri's doing cutting-edge research that
provides us with an accurate tool to assess
spore levels quickly," said Scott Foott, a
U.S. Fish and Wildlife Service pathologist.
"Without advances like this, all we can do is
limp along and quantify dead fish, which
doesn't allow us to do any innovative
Bartholomew and her colleagues have discovered
that Ceratomyxa shasta is not evenly
distributed throughout the Klamath. "The
parasite's life cycle is only established in
the main stem of the Klamath, not the
tributaries," said Bartholomew.
The OSU researchers also have found that the
dams on the Klamath appear to act as a partial
barrier to Ceratomyxa shasta.
"Above the dams, the parasite is still
present, but the severity of infection drops
off," she explained.
The research group is using information from
the new method to determine the unusual
distribution pattern. An additional clue to
its distribution may come from Ceratomyxa
shasta's unique ecology. It has two hosts –
salmonid fish and a type of aquatic worm.
"We think the distribution is determined by
habitat requirements of the worm host,"
So far, the scientists do not know how the
various tributary salmon populations are
affected by disease problems in the main stem
Klamath River. They say that knowing the
distribution pattern of the salmon parasite is
critical for future management.
Bartholomew and her colleagues are planning on
investigating why the infection is localized
in the main stem. They are also interested in
testing management actions that might reduce
One example might include a large-scale flow
experiment, not unlike the flushing flow water
releases researchers conducted from the Glen
Canyon dam on the Colorado River a few years
ago. This would allow them to better
understand how the normal hydrology of the
river system controls the number of worm
Salmon from the tributaries of the Klamath
River are distinct salmon populations and are
important to maintain each species' genetic
diversity, explained Foott. Unfortunately, the
survival rate for Ceratomyxa shasta-infected
salmonids is not good.
"If it's infected in the main stem Klamath
River," Foott said, "it's probably dead."
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