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Modeling Myxozoan Disease in Pacific Salmon: Establishing Watershed Models for Predicting Effects of Climate Change (2012-14)
Disease caused by the myxozoan parasite Ceratomyxa shasta has been shown to reduce survival of fall-run Chinook salmon in the Klamath River basin. Dr. Jerri Bartholomew’s research has demonstrated how temperature influences almost every aspect of the parasite’s life cycle. Increasing temperatures increase mortality in salmon and cause the increase the replication rates of the parasite in the polychaete host - yet higher temperatures also decrease survival of the parasite in the environment.
Dr. Bartholomew’s research has shown that river habitats, like coldwater refugia, may play a role in buffering juvenile salmon against infection. This suggests these coldwater pockets would be critical habitats for future protection. But the effects of climate change reach beyond increased water temperatures, encompassing changes in the amount and timing of spring run-off events and resulting alterations in stream flow. Incorporating all of these variables is critical to making accurate assessments on how disease dynamics will change.
This project will attempt to predict how environmental variables associated with climate change will affect the distribution and severity of ceratomyxosis in the Klamath and Willamette Rivers, so that scientists and resource managers can understand and mitigate the effects on wild salmon populations and aquaculture programs that rely on surface water. The models Dr. Bartholmew and her team are developing will have broad application in the fish health field, and could be used to examine the potential impacts of another myxozoan, Parvicapsula minibicornis, which is present in this region but currently problematic only in the northern portion of its range. The model could also help measure the potential impacts of emerging pathogens, such as viral hemorrhagic septicemia virus (VHSV), under climate change.