Poor River Conditions Lead to Gill Rot in Chinook Salmon on Lower Klamath

Information from the Yurok Tribe Facebook page:

[Photo by Jamie Holt/Yurok Fisheries Department]

Over the weekend, the Yurok Tribe’s Fisheries Department received reports of dead and dying adult Chinook salmon on the Lower Klamath River. The Department immediately mobilized monitoring crews, which observed approximately 35 dead adult salmon on a 40-mile river stretch from Blakes Riffle to Weitchpec.

According to the Fisheries Department’s preliminary analysis, the pathogen Flavobacterium columnare is the primary cause of fish mortality. Known locally as Columnaris or Gill Rot, the pathogenic bacteria rots fish’s gills until suffocation. This disease can also cause lesions on the exterior of salmon. (See photo)

[Photo by Jason Hartwick/Swiftwater Films]

“The number of dead fish is alarming but not surprising given the poor river conditions,” said Yurok Fisheries Department Director Barry McCovey Jr. “We are keeping a close eye on the river and will continue to monitor for disease and deceased fish until the conclusion of the fall run. We will be working closely with the Karuk and Hoopa Valley Tribes and our federal and state partners to assess fish health and to strategize on any necessary response.”

[Photo by Jason Hartwick/Swiftwater Films]

The current quantity of dead fish does not yet constitute a major fish kill event. The Tribe’s team of fisheries experts expect more fish to die, but it is too early to tell if there will be a catastrophic disease outbreak.

Yurok Fisheries Department biologists have also encountered numerous salmon with minor Ichthyophthirius multifiliis or Ich infections. At present, the infections are not severe enough to kill these fish. Ich is the primary pathogen responsible for killing more than 60,000 adult salmon on the Klamath in September of 2002. The 20th anniversary of the historic fish kill is in less than a month.

[Photo by Shane Anderson/Swiftwater Films]

This year’s fall run of salmon arrived early to an extremely warm and low-flowing river, which caused hundreds of fish to congregate at creek mouths where the water is cooler. When salmon stack up in this manner, disease can quickly transmit from one fish to the next. Compounding the problem, salmon are exponentially more susceptible to disease when water temperatures are high. The prognosis for the fish that amassed at the stream confluences is not good.

Earlier this month, the Yurok Fisheries Department’s monitoring crew observed salmon with sub-lethal levels of Columnaris and Ich. Concerned about a potential fish kill, the Yurok Tribe successfully advocated for additional water to be released from the Lewiston Reservoir to improve river conditions. On August 28, the additional flows arrived in the Lower Klamath River. The river rose to 2,800 cfs, where it will remain until September 21. The intent of the augmented flows is to cool the river, encourage salmon to disperse throughout the system and hopefully prevent a fish kill.

Water supplies are extraordinarily limited a result of the record drought. All summer, the Klamath was low and water temperatures reached as high was 80 degrees. Even with the infusion from Lewiston, the conditions are far from optimal. As the Klamath’s salmon run progresses up the river, we will provide regular updates on this page.

[Photo by Shane Anderson/Swiftwater Films]