[env-trinity] Eureka Times Standard 3 25 09

[Byron Leydecker]

What's ailing the Klamath's salmon?

John Driscoll/The Times-Standard

Posted: 03/25/2009 01:24:16 AM PDT

 

FORTUNA -- Researchers struggling to understand an epidemic of parasites
infecting the Klamath River's salmon raised questions and offered some
answers at a gathering of biologists Tuesday. 

Among the findings were that significantly more young salmon died faster
from the parasite called Ceratomyxa shasta during tests in the river's
disease hot spots in 2008 than the year before. 

Rich Holt with Oregon State University told a conference that chinook and
coho salmon exposed to the parasite in the most infested areas below Iron
Gate Dam to the Scott River, then taken to a lab, died faster than even
rainbow trout with no immunity. A higher proportion of salmon died, too,
nearly twice that of 2007, Holt said. 

C. shasta targets the intestines of salmon and trout. Adult fish release the
parasite's spores when they die, and the spores then move into an interim
host, a tiny polychaete worm. The worm then releases spores that are taken
in by young salmon, which often die from the parasite. 

The worm is especially prevalent just below Iron Gate Dam, and the
percentage of polychaete worms infected by C. shasta are also highest in the
reach around Beaver Creek and the Seiad Valley. Exactly why the stretch is
so rife with the parasite isn't known, said OSU researcher Jerri
Bartholomew, but it's possible that the large number of adult fish that
spawn just below the dam spread huge amounts of spores. 

"We have a situation whether the host-parasite balance is out of synch,"
Bartholomew said. 

The Klamath's salmon fishery has struggled in recent years, but last year
saw a strong run of chinook and this year's expected run is expected to be a
boom. C. shasta exists in a number of large western rivers, but in few
smaller coastal streams, but is particularly pervasive in the Klamath. 

In many cases, the work done in recent years has posed more questions than
it has answered. California-Nevada Fish Health Center researcher Scott Foott
and others in 2007 released 121 young chinook salmon implanted with radio
tags into the river below Iron Gate Dam. 

The salmon moved quickly downriver, covering the 196 miles from the dam to
Blake's Riffle near the mouth of the Klamath in just 10 days. Only 7.4
percent survived the trip. 

Considering another study by colleague Kimberly True that found exposure of
fish to C. shasta at the hot spot could be expected to kill them within
about 20 days, Foott's work suggested that the tagged fish were killed by
something else. 

But there are a number of complicating factors. In order to be able to
perform the tag surgery on the salmon, they had to be grown to a size larger
than thousands of other hatchery fish released around the same time. That
may have given them a better survival rate, especially when considering
their potential as food for predators like trout. It also remains to be seen
whether fish that travel quickly through an infested area may avoid getting
seriously ill, compared to those that linger. 

Rapid migration, lower polychaete worm density and lower water temperatures,
True found, could improve survival. 

Much more information -- even simple fisheries information -- is needed on
the river, Foott said. 

"There's so little basic fisheries survival data in the basin," Foott said. 

A recent federal spending bill earmarked some $640,000 for the National
Marine Fisheries Service to study fish diseases in the Klamath, which should
give that effort a boost.

 

Byron Leydecker, JcT

Chair, Friends of Trinity River

PO Box 2327

Mill Valley, CA 94942-2327

415 383 4810 land

415 519 4810 cell

 <mailto:bwl3 at comcast.net> bwl3 at comcast.net

 <mailto:bleydecker at stanfordalumni.org> bleydecker at stanfordalumni.org
(secondary)

 <http://fotr.org/> http://www.fotr.org 

 

 

 

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