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.

 

Map of the Deschutes River showing Warm Springs water collection sites
Deschutes River, a tributary of the Columbia River, in central Oregon. Study sites are shown as yellow diamonds. Red circles represent sites at which ISCO water sampling and sentinel fish exposures were conducted. Warm Springs water collection sites in the lower Deschutes River basin.

 

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.

 

Collecting water samples
on the Deschutes River
Filtering a water sample
using a vacuum pump
Folding the filter paper
with captured material

 

Water Sample Monitoring at Oak Springs

Density of Ceratonova shasta in water samples and water temperature Density of Ceratonova shasta in water samples at monitoring index site Pelton Trap and Oak Springs 2018

  Water Sample Monitoring at Pelton Dam

 Density of Ceratonova shasta in water samples and water temperature Density of Ceratonova shasta in water samples and water flow

 

Water Sample Monitoring Along Warm Springs River

Index sites along the Warm Springs River were established in 2017 and based on those findings, modified in 2018.