The Yurok Tribe says a decision by the U.S. Bureau of Reclamation not to implement a surface flushing flow on the Klamath River due to drought this year led to an outbreak of a deadly pathogen that likely killed large numbers of juvenile Chinook salmon, impacting runs for years to come.

The Yurok Fisheries Department monitors the river for a parasite known as Ceratonova shasta, and in recent weeks, monitoring crews found that more than 70 percent of the salmon caught in their rotary screw traps were dead.

"Available scientific information leads to the conclusion that these fish died from C. shasta," a news release from the tribe said.

The primary cause is a lack of water due to a historic drought, the tribe says. But previous water allocation decisions could have prevented the outbreak with a flow increase.

After developing a temporary operations plan for the Klamath Project due to drought conditions, BuRec announced May 12 that continuing extreme drought prompted a closure of the project's A Canal, which supplies irrigation to more than 130,000 acres of farmland, and that the surface flushing flow to help migrating salmon would not be implemented (CU No. 2004 [6]).

"While historic drought is the primary cause of the lack of water, previous [BuRec] water allocation decisions led to the widespread fish kill, which could have been prevented with a flow increase," the tribe's news release says.

The drought is also expected to cause problems for adult Chinook and coho salmon trying to return to the Shasta and Scott rivers—tributaries of the Klamath River. "In the Scott River, unless groundwater extraction is moderated, it is a virtual certainty that Chinook and Coho salmon will not be able to reach their spawning grounds due to insufficient flows for migration," the release said.

BuRec said it continues to seek input on this year's Klamath Project operation.

"The worsening forecast has revealed that anticipated water supplies may be insufficient to meet the year's remaining operational requirements for threatened and endangered species, including Upper Klamath Lake elevations for suckers and minimum flows below Iron Gate Dam for salmon," the agency said.

It is collaborating with the U.S. Fish and Wildlife Service and NOAA Fisheries, and is in consultation with the tribes to adjust the temporary plan when necessary.

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K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.