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| Under
a microscope, this is Manayunkia speciosa ,
the Klamath River worm that seems to be
passing fish-killing parasites in the Klamath
River. - Courtesy of Jerri Bartholomew, Oregon
State University |
|
Is
worm the link in Klamath fish ailment?
Researchers
trace infections to pair
Tam Moore
Capital Press Staff Writer
November 24, 2006
REDDING,
CALIF. - A tiny aquatic worm and nutrient-rich water heading
down the Klamath River in late spring may explain high
disease rates among young salmon, steelhead and trout
starting out below Iron Gate Dam.
The river management goal should be to reduce the level of
infection, Scott Foott told a panel of scientists at the
recent Klamath Conference.
"There's not one single thing we can do to change"
infection rates that sometimes hit nearly half the young
fish before they reach Seiad Valley, about 60 river miles
below the dam, Foott said.
He's a U.S. Fish and Wildlife Service fish pathologist who
heads a fishery diagnostic laboratory at Anderson, Calif.
Foott's lab chases fish disease in Oregon, California and
Nevada.
From 30 to 60 percent of salmon smolts get infected with
Certatomyxa Shasta, a parasite that lives in the little worm
known as Manayunkia speciosa. In the past three years up to
90 percent have contracted another parasite disease known as
Parvicapsula minibicornis.
"The dual infections are extremely lethal to
fish," Foott said.
And for a river where the natural fall chinook salmon
returns were so low this year that there was next-to-no
offshore commercial salmon season, and coho salmon are
already protected under the Endangered Species Act, lethal
isn't what fishermen and upstream farmers and ranchers want.
Jerri Bartholomew, an Oregon State University microbiologist
who specializes in fish disease, has chased M. speciosa in
Klamath waters the past three years. She said in a telephone
interview that the worm attaches itself to the skin of fish.
Then the tiny parasites causing C. Shasta and parvicapsula
somehow transfer to the fish.
The pursuit is a work in progress. Some pools don't show any
of the little worm in water samples taken to Bartholomew's
laboratory. Others are crawling with M. speciosa.
In laboratory tests, it has taken up to 14 weeks before the
parasite turns up in kidney tissue of young chinook salmon.
C. Shasta is found primarily in the Klamath. Parvicapsula
isn't an exclusive species to the Klamath system. It's been
recovered from farmed coho in Washington state, from
Atlantic salmon and cutthroat trout.
So little is known about some of the pathogens in the
Klamath disease cycle that scientists are still working on
basic research to establish the life cycle. Earlier this
year, Bartholomew validated the life cycle of the worm that
may cause it all. But in a paper published earlier this
year, Bartholomew notes that the worm may not be the only
host of the two fish-killing parasites.
Matt St. John, who heads the Klamath River water quality
team of the North Coast Water Pollution Control Board, said
there's a significant gap in knowledge of how M. speciosa
fits with water quality.
Headwaters to Upper Klamath Lake are rich in natural
phosphorus, which contributes to downstream algae growth.
The combination is thought to contribute to heavy nutrient
loads downstream that turn the river below Iron Gate into a
haven for the aquatic worm.
St. John said with talk of possible removal of four
downstream hydroelectric dams, there's a large knowledge
gap.
"We need models to know what would happen with dam
removal," St. John told the science panel. "And we
need a water quality model that can predict current water
quality and then look at the effect going downstream."
- Tam Moore
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