Klamath River Fish Die-off, September 2002, Mortality Report, FWS, Arcata, CA Summary of Findings This report provides an estimate of the fish mortality that occurred during the September 2002 Klamath River die-off. The intent of this report is to provide natural resource agencies and trustees with information describing the magnitude of this event for their consideration in near-term decisions regarding the affected fisheries resources and related assets under their authority. The Fish and Wildlife Service (Service), in cooperation with other federal and state agencies and Tribes, will continue to collaborate and evaluate information collected during the die-off. This report describes a conservative assessment, which probably underestimates the total number of fish that died during this event. Findings described in this report include the following: 22 The most accurate estimate of the total number of observable fish that died during the incident is 34,056. 22 Approximately 98.4 percent of the dead fish observed were adult anadromous salmonids 22 Out of 33,527 anadromous salmonids estimated to have succumbed during this event, 97.1 percent (32,533) were fall-run Chinook salmon, Oncorhynchus tshawytscha, 1.8 percent (629) were steelhead, O. mykiss, and 1.0 percent (344) were coho salmon, O. kisutch. Only one coastal cutthroat, O. clarki clarki was found dead during the investigation. 22 Approximately 91.5 percent of the coho salmon, and 38.7 percent of the steelhead observed had marks indicating that they were of hatchery origin. All hatchery coho originated from the Trinity River Hatchery. After accounting for variable tagging and shed rates, the Klamath River Technical Advisory Team (KRTAT) estimated that 7,060 (21.7 percent) Chinook were of hatchery origin. A total of 2,921 (9 percent) Chinook were of Iron Gate (Klamath River) Hatchery origin. A total of 4,139 (12.7 percent) Chinook were of Trinity River Hatchery origin. 22 The KRTAT also estimated that dead Chinook salmon represented 19.2 percent of the total (169,,297) in-river Klamath-Trinity River run. 22 Other dead fish observed during the investigation included sculpins, Cottus spp. (87 fish), speckled dace, Rhinichthys osculus (9 fish), Klamath smallscale sucker, Catostomus rimiculus (311 fish), one American shad, Alosa sapidissima, and one green sturgeon, Acipencer medirostris. ii Klamath River Fish Die-off, September 2002, Mortality Report, FWS, Arcata, CA 22 Throughout the investigation, live adult and juvenile fish of affected and unaffected species were observed in the river. In addition, some species (e.g. American shad, speckled dace, and green sturgeon) did not appear to experience extensive mortality. Almost all (greater than 99 percent) of the dead fish observed were adults or larger species offish. 22 The majority of the recently dead fish examined exhibited one or more outward gross signs of disease including gill necrosis, bacterial growth, sores, bloody vents, and ulcerations. Pathological examinations confirmed that white spot disease and columnaris were the principle immediate causes of death. Additional information collected by the Service and cooperating agencies included a suite of water quality parameters collected during the summer and fall of 2001 and 2002, fish pathology analyses, and related hydrologic information. The Service will provide reports on this additional information after it has received quality assurance review. A more comprehensive report addressing contributing factors associated with causes of the fish die-off will follow. in
"November 7, 2003."; Printed from the Internet, April 20, 2004; Includes bibliographical references (p. 43-53)