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WILLAMETTE RIVER BASIN RESEARCH
The Bartholomew Lab is involved in several fish pathogen studies in the Willamette Basin.
Distribution of Ceratomyxa shasta
Parasites and diet of non-native fishes
Disease risks associated with hatcheries in the Willamette River Basin
Ceratomyxa shasta is a myxozoan parasite that causes intestinal hemorhaging and necrosis in salmon and trout. It is found only in the Pacific Northwest of North America. In the Willamette River, it has been a problem in different years, especially when temperatures are high and water flows are low. It has been associated with mortality in outmigrating juveniles and in returning adult fishes. Salmonids in this basin include anadromous Spring Chinook (endangered) and winter steelhead (listed) and resident cutthroat trout and rainbow trout. Previous studies have found the fish-infectious stage as far upstream as Mary's River, Corvallis. We are further defining where the parasite is found in this system and identifying areas of high abundance by measuring its density in river water samples.
River water is simultaneously collected using automatic samplers at four river sites each week. The samplers collect 1L every 2 hours for 24 hours from which 4 1L replicates are then manually taken. The water is filtered, any DNA present extracted and tested for Ceratomyxa shasta. The molecular assay, a probe-based qPCR, indicates how much of the target pathogen is present in each sample.
Once a year, the entire Bartholomew Lab is involved in an intensive manual spatial sampling of the river, from its mainstem origin near Eugene, down to the confluence with the Columbia River. These data provide information on the spatial and temporal occurence of the parasite in this basin.
Researchers: Luciano Chiaramonte & Jerri Bartholomew
Research funded by: Oregon Sea Grant.
The Bartholomew Lab also monitors this parasite in the Klamath River Basin.
In coordination with a long-term OSU Fisheries and Wildlife landscape-scale study of the Willamette River Basin (PI = Stan Gregory), we are examining non-native warm-water fish species.
We want to answer two primary questions:
1. What myxozoan parasites are in the non-native fishes?
2: Are the larger non-native fish eating juvenile salmonids?
We want to determine if the non-native fishes have the same parasites as the local fishes, or do they have unique species that may have been co-introduced with their hosts? We are focusing on myxozoan parasites, and have found that these parasites are specific to their hosts, and were probably co-introduced with the fish. The parasites do not appear to infect native fishes. Table of 2011 results.
We examine the stomach contents of all of the larger fish (primarily bass) and frequently find that they have eaten smaller fish, crustaceans and molluscs. It is often difficult to identify the type of fish that has been eaten (due to the effects of digestion) and we are looking at using DNA-based methods to identify the prey species.
Myxozoan parasites found in Willamette River non-native fishes
host yellow perch
gut contents of a bass
Researchers: Stephen Atkinson & Jerri Bartholomew
Hatcheries and fish released from hatcheries are assumed to serve as sources of pathogens responsible for declines in naturally reared fish populations. On the other hand, hatcheries serve as good indicators of what pathogens are present in natural populations residing in hatchery water supplies. The aim of the proposed research is to evaluate pathogen transmission between hatchery and naturally reproducing populations, and the degree of pathogen amplification that occurs in hatcheries. A variety of pathogens have been associated with disease outbreaks in hatcheries in the Willamette River system. All of these hatcheries use surface water that adult salmon migrate through. Water treatment is limited to Leaburg Hatchery, where inflow to the hatch house undergoes ultraviolet irradiation (UV), and Willamette Hatchery, which has the potential for limited use of UV treatment of effluent from the egg incubation/isolation facility.
This study will inform hatchery operations by determining if disease risks support the use of water disinfection of hatchery influent or effluent. In addition, it would address information gaps that would further our understanding of disease interactions between hatchery and wild fish. We propose to use an approach that will combine use of sensitive molecular methods for detection of specific pathogens in water with increased surveillance of naturally reproducing/wild fish stocks and sentinel fish to provide information on the types and levels of pathogens released from hatcheries. Disease risk is also a function of temperature, and water temperatures will be simultaneously monitored at each location. Findings of this study will be developed as a risk assessment for each hatchery, evaluating the evidence for transmission from hatchery fish to wild fish, wild fish to hatchery fish and the potential for population impacts.
1. Document pathogens in naturally reproducing/wild fish present above and below hatchery water supplies.
2. Determine if there is a difference in transmission of selected fish pathogens to naive sentinel fish above and below facilities.
3. Determine the presence and relative abundance of selected fish pathogens above, in, and below the hatchery by screening water samples.
4. Compare parasites and pathogens found in naturally reproducing/wild populations, sentinel fish and water with those present in the hatcheries on those systems using ODFW fish health monitoring information.
5. Evaluate the evidence for transmission from hatchery fish to wild fish, wild fish to hatchery fish and the potential for population impacts.
6. Develop risk assessments for Willamette River Hatcheries.
Researchers: Michelle Jakaitis, Sean Roon, Sascha Hallett, Gerri Buckles, Rich Holt & Jerri Bartholomew
Research funded by: US Army Corp of Engineers and the Oregon Department of Fish and Wildlife