short stories / By Heidi Walters

About a Worm

Researchers hone in on parasite-ridden Klamath River hotspots

(Feb. 8, 2007)  A mid last week’s news that the fed-eral government has mandated in-stallation of fish ladders as a condition of the government’s relicensing of PacifiCorp’s Klamath dams, some of the region’s top fisheries scientists gathered in Fortuna to talk about a worm.

They met for two days to swap information about a tiny, translucent, squid-shaped class of worm known as a “polychaete” - specifically, Manayunkia speciosa, which studies have found to play a key role in the ongoing mass die-offs of juvenile Chinook salmon on the Klamath River. (These juvenile deaths are not to be confused with the 2002 adult fish die-off that grabbed everyone’s attention, which involved a different set of problems.)

The scientists noted in passing the federal fish prescriptions for dam relicensing, but they were more excited by breakthrough studies that have been conducted by Oregon State University researchers out of Corvallis on the juvenile fish deaths. The OSU folks have been focusing on the Klamath’s outmigrating juvenile Chinook, who’ve been dying in high numbers each spring from infection by a parasite called Ceratomyxa shasta - 40 to 90 percent of the juveniles die before they can reach the ocean. And the buzz during the cocktail hour after Wednesday’s presentations was particularly infused with praise for what that young Rick Stocking of OSU had found while scraping about underwater in the Klamath looking for the worm that is the intermediary host to C. shasta.

Scientists have known for a couple decades that C. shasta causes ceratomyxosis, a fatal disease, in Pacific Northwest trout and salmon. Tribal fisheries biologists on the Klamath first noticed the juvenile deaths from C. shasta infection in the early 1990s. Scientists have also known, for years, about the presence of the polychaete worm.

But it wasn’t until 1997 that microbiologist Jerri Bartholomew, of OSU’s Center for Fish Disease Research, and her team of researchers discovered that C. shasta requires the polychaete worm, in addition to the salmon, to complete its life cycle. Her lab has also used cutting-edge DNA techniques to pinpoint occurrences of C. shasta‘s spores in the Klamath River - they found spores throughout the river, with some locations containing an especially high quantity. But still nobody knew much about the worm. Which is where Stocking came in.

“In 2003, [Bartholomew] posted a position for a graduate student to investigate where the polychaete is in the river, and what habitat it lives in,” said Stocking, after the conference. “And I was interested in host-parasite ecology in an environment and, if that environment changes, how does it interfere with the host-parasite interaction? The Klamath was the perfect setting, because the Klamath River is a nutrient-rich system that has been modified.”

Stocking said he knew that parasites had become a huge issue in fish farms. “I was curious, because fish seemed to be doing pretty well out in the environment - at least before we started mucking around with rivers. Whereas in the hatchery systems, they battle with [the parasites] every year. There’s crowding and a lot of opportunities for pathogens to move from fish to fish, and the fish are stressed out.”

So what exactly was going on in the Klamath?

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