Polychaete Laboratory Work
June 2008 - May 2011
- Yurok Tribal Fisheries Program
Fish diseases are widespread in the mainstream Klamath River and strong evidence suggests that disease levels are adversely affecting the freshwater production of salmonid fishes. In recent years, researchers have documented large numbers of emigrating juvenile Chinook salmon and coho salmon infected by one or both myxosporen parasites - Ceratomxya shasta and Parvicapsula minibicornis. The high infectivity rates observed in native salmonid species in the Klamath River suggests a parasite-host imbalance where environmental conditions have favored these parasites. Lifecycles of C. shasta and P. minibicornis are complex, but both parasites are dependent on the freshwater polychaete worm Manayunkia speciosa, and on salmonid fishes as alternate hosts to perpetuate their life cycle. Potential management strategies to reduce disease prevalence have centered on identifying factors that may interrupt some segment of the parasite lifecycles in order to bring the parasite-host equilibrium back into balance. Whereas several studies have examined factors affecting fish infectivity within the Klamath River basin, studies on the ecology, distribution, abundance, and infection prevalence of the polychaete host are in their infancy. Polychaete colonies exhibit a patchy distribution within the Klamath River and occur in low velocity areas comprised of sand-silt embedded with fine organic matter. The polychaete also often occurs in association with mats of filamentous algae, particularly Cladophora, and beds of vascular plants. In addition to further study of polychaete life history and factors limiting their distribution, there is a critical need to more accurately and further document the infection prevalence of polychaete populations throughout the Klamath River mainstem before proceeding to develop or implement management strategies.