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Department of the Interior

U.S. Fish & Wildlife Service

California/Nevada Operations Office

2800 Cottage Way, Room W-2606

Sacramento, California 95825

Press Release  


For Immediate Release

November 18, 2003


 For more information, visit our Web site at http://sacramento.fws.gov


New U.S. Fish and Wildlife Service study says “combination of factors”

caused salmon die-off in Klamath River in 2002


            An unusual combination of factors -- including a high density of congregating fish, low flows, warm temperatures and a delayed upstream migration -- sparked a disease epidemic that led to the loss of more than 34,000 salmon and other fish in the Klamath River in 2002, according to a study released today by the U.S. Fish and Wildlife Service.


The study attributes the direct cause of death for most of the fish to an outbreak of two freshwater pathogens, Ich and columnaris. Both pathogens are commonly found in the Klamath River, so additional factors combined to stress the fish and increase their susceptibility to the pathogens. The report says those factors included:


·        The large size of the fall run of Chinook salmon returning to the Klamath River from the Pacific Ocean. The run was the eighth largest for the period from 1978 to 2002.

·        High densities of fish in the lower river, which allowed the pathogen outbreaks to spread quickly. Large numbers of fish congregated in the lower river one to two weeks earlier than normal, but a lack of rainfall or freshwater pulses left the fish with no cues to begin their upstream migration.

·        Relatively low flow in the lower Klamath River. Average monthly flow in 2002 was the fifth lowest in the period from 1978 to 2002.

·        Hot weather, which left water temperatures higher than optimum for salmon.


Fish and Wildlife Service Director Steve Williams praised the scientists who prepared the report, which took more than a year to complete and was the subject of a rigorous internal peer review.


“Our team of scientists conducted an exhaustive, multi-faceted study of this loss of Klamath River fish,” Williams said. “Its findings, which are based on the best available scientific data, are consistent with those of the recent National Research Council report. Both reports conclude that the river’s troubles are due to a multitude of factors, and improving the river will require a watershed effort by Federal and State agencies, the Tribes, and other stakeholders.” 


The die-off, which occurred from late September to early October 2002, was the largest loss of pre-spawning adult salmon ever recorded in the Klamath River and one of the largest on the West Coast. The river originates in Oregon’s Upper Klamath Lake, flowing more than 250 miles through southern Oregon and northern California before entering the Pacific Ocean.


Most of the dead fish – about 97 percent – were fall-run Chinook salmon. About 2 percent were steelhead and 1 percent were coho salmon. The lost fall-run Chinooks represented about 19 percent of the total run of nearly 170,000 fish in the Klamath River and its largest tributary, the Trinity River. A related Fish and Wildlife Service report, which provides an estimate of the total number of fish lost at just over 34,000, is also being released today.


Both reports can be viewed or downloaded at the Sacramento Fish and Wildlife Office’s Web site at http://sacramento.fws.gov/




The U.S. Fish and Wildlife Service is the principal Federal agency responsible for conserving, protecting and enhancing fish, wildlife and plants and their habitats for the continuing benefit of the American people. The Service manages the 95-million-acre National Wildlife Refuge System which encompasses 542 national wildlife refuges, thousands of small wetlands and other special management areas. It also operates 69 national fish hatcheries, 64 fishery resource offices and 81 ecological services field stations. The agency enforces Federal wildlife laws, administers the Endangered Species Act, manages migratory bird populations, restores nationally significant fisheries, conserves and restores wildlife habitat such as wetlands, and helps foreign governments with their conservation efforts. It also oversees the Federal Aid program that distributes hundreds of millions of dollars in excise taxes on fishing and hunting equipment to state fish and wildlife agencies.





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