[env-trinity] CBB: PARASITE-DRIVEN DISEASE HITTING KLAMATH SALMON HARD ALSO FOUND TO LESSER DEGREE IN COLUMBIA BASIN

Mon Aug 25 10:50:10 PDT 2014

http://www.cbbulletin.com/431827.aspx

Parasite-Driven Disease Hitting Klamath Salmon Hard Also Found To Lesser
Degree In Columbia Basin 
Posted on Friday, August 22, 2014 (PST) 

Some spring chinook salmon adults returning to the Willamette and Deschutes
river basins have been found to be infected by Ceratomyxa shasta (c.
shasta), a parasite-driven disease that is contracted by the fish while in
the river and that can kill adults before they spawn.

While it's not unusual for the parasite to reside in rivers of the Columbia
River basin-- such as the Lewis, Cowlitz, Willamette and Deschutes rivers
and up through the Snake River basin --this year with warmer water and lower
flows, the damage to spring chinook is more severe.

Since 2002, c. shasta has devastated salmon in the Klamath River in southern
Oregon and Northern California, where this year, due to extremely low flows
and warm water, the parasite has invaded more than three quarters of
juvenile out-migrants. 

While the severity does not match that of the Klamath River, researchers are
still finding infected adult fish in at least two Columbia River basin
streams, according to Craig Banner, senior fish health specialist, Fish
Health Services, Department of Microbiology, Oregon Department of Fish and
Wildlife.

Banner said that fewer spring chinook salmon than expected have returned
this year to Warm Springs and Round Butte fish hatcheries on the Deschutes
River in Central Oregon and that some that did return had signs that c.
shasta was taking its toll. He was hesitant to point to the parasite as the
cause of the overall poor return of fish on the Deschutes River. Many of the
fish, he said, had rough gills as a result of another pathogen. "The bottom
line is that not as many fish came back this year," he said.

However, Willamette River spring chinook salmon are showing signs of harsher
physical damage.

"c. shasta is always present and we always find it in a portion of the adult
fish," Banner said. "However, this year, in a portion of our adult fish, the
parasite seems to be causing more dramatic pathogenic damage."

The parasite usually settles in the intestines of fish, both juvenile and
adult fish that have been exposed. This year, he said, biologists studying
adult spring chinook salmon in the Willamette River are also seeing more of
the parasite in livers, spleens and kidneys of the fish, even though chinook
salmon are "somewhat resistant" to the effects of the parasite.

"Resistance, however, is related to how much the fish is exposed to the
parasite," he said. "Unusually high exposure leaves them less resistant to
the disease." 

He is not sure why there would be a higher exposure of the parasite to
salmon this year, but pointed to stream conditions, warmer water and lower
flows, as having the potential to increase the presence of c. shasta. 

"These are bad conditions for fish, but good conditions for the parasite,"
he said.

For adult salmon, there is little visual indication to the lay person that
c. shasta parasites reside within the fish, nor is there any particular
damage to the flesh of the fish, and eating the fish is not harmful to
humans, Banner said. 

Once the salmon picks up c. shasta from the water, incubation to
full-fledged parasite takes 14 to 40 days before a salmon could die. The
fish could have picked up the parasite anywhere along their journey to
spawning after they arrive in the fresh water of the Columbia River. Or,
they may have been exposed in the Willamette River or the Deschutes River,
where warmer water and lower flows are more conducive to the parasite's
presence.

ODFW has not completed field studies to determine the full impact this year
of the parasite on adult or juvenile salmon populations in the Willamette
River. However, it is collecting pathology samples from the intestines,
liver, spleen and kidneys of fish in the river. 

In addition, one of the leading authorities on c. Shasta is collecting water
samples in the Willamette River, looking at the presence of c. shasta in the
water. Professor Jerri Bartholomew, director of the John L. Fryer Salmon
Disease Laboratory at Oregon State University, did graduate work on the
parasite in the late 1980s. For more than a decade she has been especially
busy leading research of c. shasta in the Klamath River Basin, where the
parasite is far more prevalent and damaging to fish runs.

Bartholomew confirmed that temperature and flow has a lot to do with the
severity of the infection, pointing to conditions in the Klamath River,
where extreme low flows and high water temperatures caused by an
exceptionally poor snow pack this winter, are devastating salmon. 

Nick Hetrick, supervisory fish biologist (Fisheries Program Lead), at the
U.S. Fish& Wildlife Service's Arcata, Calif. office, said the snow pack in
the upper Klamath River was as low as 15 percent of normal this year, but
the Trinity River's snowpack, which flows into the Klamath River further
downstream, was near zero. 

A survey this summer of juvenile fall chinook out-migrants in the Klamath
River found that c. shasta was present in 76.5 percent of chinook salmon
juveniles and that another parasite, Parvicapsula minibicornis, was detected
in 86 percent of juveniles (
<http://www.fws.gov/Arcata/fisheries/projectUpdates/FishHealthMonitoring/Kla
math%20Juvenile%20Salmonid%20Health%20Update%20July%2028%202014.pdf>
http://www.fws.gov/Arcata/fisheries/projectUpdates/FishHealthMonitoring/Klam
ath%20Juvenile%20Salmonid%20Health%20Update%20July%2028%202014.pdf). Last
year, c. shasta was present in just 5 percent of fish. The impact of the
parasite on juveniles is more visually apparent than in adult fish, as they
develop soft flesh and distended stomachs since the parasite inhabits the
intestines of fish.

Neither Hetrick nor Bartholomew would predict the impact of the infection in
juvenile fish on actual adult returns, but both said it could be
significant.

Bartholomew also has conducted water surveys in the Klamath River, similar
to the surveys she is conducting in the Willamette River. In 2013, her crew
of researchers found c. shasta in the water six out of the 12 weeks of the
survey. This year they found the parasite in each of the 12 weeks. On the
Klamath River, when parasite abundance is greater than 10 parasites for
every liter of river water, it triggers a pulse of water from upstream dams
to cool the river and reduce what are ideal conditions for the parasite.
That occurred this year in May, but it was a small pulse of water and the
basin has very little water to continue these pulses, she said.

c. shasta has long been a presence in the Columbia River watershed (see
"Geographic distribution of Ceratomyxa shasta in the Columbia River basin
and susceptibility of salmonid stocks" by Bartholomew at
<https://ir.library.oregonstate.edu/xmlui/handle/1957/21962>
https://ir.library.oregonstate.edu/xmlui/handle/1957/21962

However, this is the first time that researchers have collected water
samples in the Willamette River and there isn't any river in the Columbia
River basin in which c. shasta abundance would automatically trigger a pulse
of water to cool the river as in the Klamath River.

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