Evaluation of Ceratomyxa shasta and Parvicapsula minibicornis infection in returning adult chinook salmon (Oncorhnychus tshawytscha) throughout the Klamath River Basin

I examined incidence and density of Ceratomyxa shasta and Parvicapsula minibicornis infection in adult Chinook salmon (Oncorhynchus tshawytscha) returning to spawn in the Klamath River Basin. From August 2007 through December 2007, 506 adult salmon were sampled at various locations throughout the basin. Trophozoite and myxospore life stages of the myxozoan parasites C. shasta and P. minibicornis were identified and quantified using wet mount, histology, and polymerase chain reaction. Chi-square tests were used to correlate any temporal or geographical patterns with incidence and density. Incidence and density for both pathogens peaked on October 25 in samples collected from Iron Gate Hatchery. No clear trends were seen in samples collected from Trinity River Hatchery. Chinook salmon carcasses collected from Bogus Creek, Shasta River, and the mainstem Klamath River were found to have significantly more C. shasta myxospores than Chinook salmon artificially spawned at Iron Gate and Trinity River Hatcheries. Further research should focus exclusively on naturally-spawned salmon carcasses to gain a better understanding of the timing and frequency of the myxospore load in the Klamath River Basin.