Archived, Siskiyou

The Klamath River September 2002 Fish Die-off : Older Fish from Trinity River Hatchery Affected ​

Report on Estimate of Mortality
Report Number AFWO-01-03

In September 2002, a devastating fish die-off occurred in the lower Klamath River, prompting an investigation by the U.S. ​ Fish and Wildlife Service (USFWS) and other agencies. ​ This article aims to provide an overview of the die-off and highlight the significant presence of older fish from the Trinity River Hatchery among the casualties. ​

Summary of Findings: The USFWS report on the estimate of mortality revealed that a total of 34,056 observable fish died during the incident. ​ The majority of the dead fish, approximately 98.4 percent, were adult anadromous salmonids. ​ Out of the estimated 33,527 anadromous salmonids that succumbed, 97.1 percent were fall-run Chinook salmon, 1.8 percent were steelhead, and 1.0 percent were coho salmon. ​ Only one coastal cutthroat was found dead during the investigation. ​

Significance of Trinity River Hatchery: ​ The report highlighted that a significant proportion of the dead Chinook salmon were of hatchery origin, specifically from the Trinity River Hatchery. ​ Approximately 12.7 percent of the Chinook salmon deaths were attributed to fish from this hatchery. ​ After accounting for variable tagging and shed rates, the Klamath River Technical Advisory Team (KRTAT) estimated that 7,060 Chinook salmon (21.7 percent) were of hatchery origin. ​

Older Fish Affected: ​ One notable finding was that the fish affected by the die-off were predominantly older fish. ​ The report mentioned that almost all (greater than 99 percent) of the dead fish observed were adults or larger species of fish. ​ This indicates that the mortality primarily impacted mature fish populations in the Klamath River. ​

Causes of Mortality: The investigation revealed that the majority of the recently dead fish exhibited outward signs of disease, including gill necrosis, bacterial growth, sores, bloody vents, and ulcerations. ​ Pathological examinations confirmed that white spot disease and columnaris were the principal immediate causes of death. ​

Collaboration and Acknowledgments: The investigation and report were a collaborative effort involving the U.S. Fish and Wildlife Service, California Department of Fish and Game, Yurok Tribe, Hoopa Valley Tribe, and the Klamath River Technical Advisory Team. ​ The report acknowledged the contributions and reviews provided by these organizations in the investigation and drafting of the report.

Conclusion: The fish die-off in the lower Klamath River in September 2002 had a significant impact on the adult anadromous salmonid population, particularly fall-run Chinook salmon. ​ The presence of older fish from the Trinity River Hatchery among the casualties highlights the vulnerability of hatchery-origin fish during such events. ​ The findings of this report will aid trustees in making informed decisions regarding the affected fisheries resources and related assets under their authority. ​

Note: The information in this article is sourced from the provided document.

Leave a Comment

Your email address will not be published. Required fields are marked *