Deschutes River
Ceratonova shasta monitoring studies in the Deschutes River Basin
Ceratonova shasta is a freshwater, myxozoan parasite that is native to the Pacific North West of North America. It causes enteronecrosis in salmonids which, in the Deschutes River Basin, has resulted in high mortality in cultured juvenile salmon at the Pelton Facility and in adult salmon returning to both the Round Butte and Warm Springs hatcheries. Transmission occurs through waterborne stages: actinospores released from polychaete worms infect salmonid fishes and develop into myxospores which then infect polychaetes (see life cycle on left). The parasite proliferates in each host (not in water).
“By understanding the relationships between the parasite, its hosts, and the natural habitats and conditions that are favorable or unfavorable for infection, strategies can be developed to limit the exposure of fish to areas where the risk of infection of C. shasta may be higher, or develop management strategies based upon predicted water and climate conditions to improve the survival and viability of wild and hatchery salmonids.” Cyndi Baker, PhD, CTWSRO.
Through collaboration with the Confederated Tribes of the Warm Springs Reservation of Oregon (CTWSRO), USFWS, and ODFW we have developed a parasite monitoring program which contributes to our understanding of the role of pathogens (such as Ceratonova shasta) in juvenile and pre-spawn mortalities of adult Spring Chinook salmon of the Deschutes River Basin. Monitoring is primarily through quantification of waterborne stages of the parasite.
Water samples
We conduct two types of water sampling to provide high resolution data on the spatial and temporal abundance of Ceratonova shasta – regular monitoring as well as spatially intensive sporadic longitudinal sampling. Collection of river water samples for regular monitoring occurs at two index sites established in 2015; once a week all year round at Oak Springs and every other week from April through October at Pelton Dam (sites marked in red on map above). Beginning in 2017, monitoring will occur at a further 8 sites that span from the town of Bend to Heritage Landing at the mouth of the Deschutes River (see map above). Longitudinal sampling occurs approximately twice a year (in spring and summer) at 16-24 sites.
At the established index sites, solar-powered automatic samplers (ISCOs) collect 1L of water every 2 hours for 24 hours, from which 4 1L samples are manually taken, whereas samples are collected manually at the remaining index and longitudinal sites. Regardless of collection method, each 1L sample is filtered through a 5-micron nitrocellulose membrane using a vacuum pump, and any captured DNA in 3 of the replicate samples is extracted using a kit. A quantitative PCR (qPCR) specific for C. shasta is used to detect and quantify any parasite DNA present (Hallett & Bartholomew 2006). Cq values generated by the qPCR are converted to numbers of parasite spores per liter of water using reference samples with known quantities of spores. The Warm Springs tribal biologists and members of ODFW are integral to the collection and filtration of the ISCO water samples.
Temporal water sample monitoring at Oak Springs (first) and Pelton Trap (second)
Water sample monitoring on the Warm Springs River
Longitudinal Water Sampling Schedule
- August 17th, 2015
- June 7th and August 30th, 2016
- June 6th and August 30th, 2017
- May 2nd, June 5th, July 10th and August 29th, 2018
- June 13th and August 30th, 2019
Genotyping
There are multiple genetic types of C. shasta simultaneously present in the Deschutes River Basin (Stinson & Bartholomew 2012). While genotype I infects our target species (Chinook salmon) most commonly, we will be analyzing samples for all genotypes of C. shasta. We do this by amplifying the variable ITS1 region using a PCR assay and then we sequence that amplicon (Atkinson & Bartholomew 2010). From the sequencing chromatogram, we can determine the proportion of each genotype present in a sample. We use the total spore density to then determine the number of spores of each genotype in a sample.
Thus, in addition to determining the abundance of total C. shasta in the river, we will also determine the relative proportions of the various genotypes and their spatial and temporal distributions. These data will be aligned with salmonid migration (juveniles and adults) to investigate whether parasite genotype abundance corresponds with the life history of its salmonid host.
Predicted genotypes
Our hypotheses were that C. shasta genotype abundance and corresponding salmonid host abundance would be correlated. We also explored the hypotheses from Stinson and Bartholomew (2012) that there would be a correlation between the spatiotemporal distribution of genotypes and salmonid hosts with type I in the upper basin (between the Round Butte Dam and DBF) with the reintroduction of Chinook salmon. Using fish passage data provided by PGE in combination with genotyped fish tissue data from Stinson and Bartholomew (2012), the expected results of these hypotheses are displayed graphically below. This figure does not account for resident trout populations (which carry type O and II) as they have not been quantified in the Deschutes River.
Invertebrate host studies
In 2019, polychaetes were collected concurrent with the second longitudinal water sampling at a subset of water sites to capture expected variation in polychaete abundance, C. shasta infection prevalence, C. shasta density and geomorphology. Based on the information about spatial distribution of waterborne C. shasta in the Deschutes River in 2015-2019, we targeted three sites from each of three categories: low, moderate, and high C. shasta, stratified throughout the basin. Sampling occurred at 9 different sites along the Deschutes River on August 27th (refer Table 3). Three samples were collected at each site using Hess. Sorting of the samples in the laboratory is underway.
References
Atkinson and Bartholomew (2010) Disparate infection patterns of Ceratomyxa shasta (Myxozoa) in rainbow trout Oncorhynchus mykiss and Chinook salmon Oncorhynchus tshawytscha correlate with ITS1 sequence variation in the parasite. International Journal for Parasitology 40:599604
Hallett SL, Bartholomew JL (2006) Application of a real-time PCR assay to detect and quantify the myxozoan parasite Ceratomyxa shasta in river water samples. Diseases of Aquatic Organisms 71:109-118.
Hallett SL, Ray RA, Hurst CN, et al. (2012) Density of the waterborne parasite Ceratomyxa shasta and its biological effects on salmon. Applied and Environmental Microbiology 78:3724–3731.
Stinson MET and Bartholomew JL (2012) Predicted Redistribution of Ceratomyxa shasta Genotypes with Salmonid Passage in the Deschutes River, Oregon. Journal of Aquatic Animal Health 24:274-280.
These research efforts are possible through contribution (funding and efforts) provided by: CTWSRO, CRITFC-PCSRF (research and graduate support 2017-2018), ODFW (Graduate Fellowship 2015-2016 & 2017-2018), LCRFHC-USFWS
For an overview of Deschutes River studies (sentinel fish exposures and water sampling) conducted in 2015 and 2016, please click on the following link: “ODFW Fellowship Report 2015-2016”
For further details about the research conducted in 2017 and 2018, please refer to Kalyn Hubbard's MS thesis: Spatiotemporal Distribution of Ceratonova shasta and its Genotypes in the Deschutes River Basin
2019 Annual report
2017-2018 Final Report
Data shared here are preliminary and subject to modification.
Image credits: Kalyn Hubbard, Stephen Atkinson.