GRANS PASS, Ore. (AP) — A deadly salmon parasite is thriving in the drought, infecting nearly all the juvenile chinook in the Klamath River in Northern California as they prepare to migrate to the ocean.
The Klamath Fish Healthy Advisory Team, made up of state and federal agencies and Indian tribes, warns a major fish kill is likely, and the Yurok Tribe and NOAA Fisheries Service have asked for extra water releases to flush out worms that carry the parasite, known as C shasta.
But the U.S. Bureau of Reclamation says after four years of drought, it has no water to spare for chinook salmon.
Bureau spokeswoman Erin Curtis said Wednesday the water stored in Klamath Basin reservoirs is already committed to endangered sucker fish and threatened coho salmon, and releasing water now means less for any crisis that erupts this summer.
Water for farmers on a federal irrigation project has also been cut to less than half of full deliveries as mountain snowpacks that supply reservoirs have dwindled to zero.
“We made the decision after consulting fish health experts and reviewing records that releasing a pulse flow at this time was not an advisable use of a very limited water supply,” Curtis said. “We are having to take the long view. We know we have got to get through the whole spring and summer. There are going to be a lot of decisions to make, and this is one of them.”
Demand for water will increase again when adult salmon return to spawn in late summer and face infection from a different disease that rots their gills.
The parasite, whose full name is Ceratomyxa shasta, occurs naturally in the Klamath, but the worm that serves as a host thrives when water gets warm and flows are reduced, which is the case during drought, said Jerri Bartholomew, professor of microbiology at Oregon State University. She said sampling shows nearly 100 percent of juvenile chinook are infected, though not all of them will die. Coho salmon, which are infected by a different strain of the parasite, have so far been spared.
“This is turning out to be as bad as the worst year since we have been monitoring, which is 2004,” Bartholomew said. “The only year parasite levels approached what we are seeing this year was 2008, and that year they didn’t get this high until June.”
Water samples show C Shasta spores reached lethal levels in April and since then have gotten worse, she said.
The C Shasta outbreak has only affected young chinook, and has not affected young coho, which are infected by a different strain, Bartholomew added.
Meanwhile, the Iron Gate fish hatchery is waiting to release some 6 million juvenile chinook in hopes conditions may improve, said NOAA Fisheries Service spokesman Michael Milstein.