Ecology of Ceratomyxosis in the Klamath River

The myxozoan parasite Ceratomyxa shasta causes losses among both wild and hatchery-reared juvenile salmonids in the Pacific Northwest. It is a significant pathogen in the Klamath River, where it has been identified as a key factor limiting salmon recovery. In this river, we hypothesize that a highly regulated water flow regime and warm water temperatures, combined with limited locations for adult spawning, have resulted in an ideal habitat for this parasite. Monitoring studies involving sentinel fish exposures, polychaete sampling and water analysis have increased our understanding of the temporal and spatial distribution of the parasite and moved us closer to reaching management goals of reducing mortality in native stocks. Water sampling in particular, has proven to be a simple, high resolution tool for mapping total parasite density in river water. Water samples collected using automated sampling devices are filtered, the captured DNA extracted and C. shasta quantified by a TaqMan qPCR, providing a measure of parasite spores per liter of water. The resulting data has allowed us to define an area of the river of high risk for infection of juvenile salmon.  Combined, these data sets are allowing us to examine relationships between fish mortality, parasite density, parasite genotype, water temperature and flow. Additionally, monitoring opportunities such as a planned pulsed flow event have allowed us to test hypotheses about the critical habitat for the parasite’s invertebrate host, the polychaete Manayunkia speciosa, and to begin to develop a hydrologic model that will ultimately provide information on the timing and magnitude of flow events necessary to disturb this habitat and decrease abundance of this host.