Deschutes River Ceratanova Shasta Presence Evaluation II

This project was an extension of the 15-Warm-04 project, which investigated the presence, abundance, and sources of Ceratonova shasta (C. shasta), a myxosporean parasite that infects salmonids in the Pacific Northwest through water samples. This next phase (16-Warm-05) investigated more directly into C. shasta infections in juvenile and adult spring Chinook. Climate variables, such as water temperature and streamflow, were correlated with the C. shasta results to determine the connections and recommend conservation measures for declining spring Chinook redds in Reservation streams.

Ceratonova shasta is the most serious pathogen threat for spring Chinook in the Deschutes River. Recent results from USFWS/OSU (2016) indicated high C. Shasta spore concentrations in the lower Deschutes River and that outmigrating juvenile spring Chinook from Warm Springs River (WSR) are susceptible to exposure. In an experiment that exposed juvenile spring Chinook to C. shasta and monitored prevalence of infection in mortalities and survivors, Warm Springs spring Chinook had low resistance to mortality once exposed. C. shasta has been known to cause high rates of mortality in spring Chinook at Warm Springs National Fish Hatchery (WSNFH) as returning adults, likely infected with C. shasta as smolts, hold in tanks with warm water temperatures. C. shasta becomes infective at temperatures around 10oC but increases in virulence as temperatures increase (CDWR 1988). With low redd counts of spring Chinook in Warm Springs River relative to escapement past WSNFH, it is suspected that pre-spawning mortality of Chinook is occurring during adult holding period where they remain in deep pools in the canyon reach of WSR from May through August. In this holding area, temperatures reach 10oC by April and often exceed 20oC.

Phase I was funded as project 15-Warm-04.

Phase II (this proposal) accomplished the following: 1) Inspect juvenile spring Chinook in rotary screw traps in WSR and request separation by code at Bonneville Dam for inspection after migration through Deschutes River (hypothesis to be tested is spring Chinook smolts have no infection in WSR but will have infection at Bonneville Dam suggesting that they became infected in lower Deschutes River); 2) Survey in the Warm Springs Canyon to observe adult spring Chinook holding and recover any carcasses to test for presence of C. shasta (hypothesis to be tested is that adults that may have been infected as smolts hold in the canyon from May –August prior to spawning, water temperatures become warm activating C. shasta); 3) Target areas of potential C. shasta infection to sample polychaete worms in the substrate, on rocks, and in filamentous green algae to test if they are infected with C. shasta; 4) Determine which genotype of C. shasta is present in the Deschutes Basin; and 5) Validate a model developed by OSU/USFWS that predicts degree-days to mortality using parasite density, streamflow, and which C. shasta genotype (genotype I, high mortality in Chinook; genotype II, high mortality in coho) is present. This level of funding is likely not going to answer all the questions about C. shasta in the Deschutes River and Reservation streams but it will contribute greatly to development of study design for future studies given the lack of information presently.

Phase II PCSRF funds were used to subcontract with OSU Dept. of Microbiology for performing qPCR assays of juvenile spring Chinook (Objective 1), adult carcasses (Objective 2), polychaetes (Objective 3), genotyping C. shasta spores on filters from water samples (Objective 4), taking data from Phase I and II of this effort, combined with past and on-going efforts of OSU/USFWS in the Deschutes River and validating parasite risk assessment models for spring Chinook (Objective 5), and to provide recommendations for how management may reduce mortality in spring Chinook given risk of infection with respect to water tempera

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.

In addition to the fish host, C. shasta infects a freshwater polychaete worm. Actinospores are released from the worm, and infect fish, on contact, in the water column. Neither horizontal (fish to fish), nor vertical (fish to egg) transmissions have been documented under laboratory conditions, suggesting that the worm host is necessary for completion of the life cycle.
Research indicates that the potential for infection is enhanced when water temperatures are high, water flow is low, or numbers of infectious C. shasta are relatively high in the water column. Infection rates appear to be higher in or below still water environments than riverine ones. C. shasta can infect salmonids in a variety of ways, both internally and externally, and its effects on individual fish may range from mildly debilitating to fatal.

Salmonids may be infected by the parasite at any developmental stage and at multiple locations. The natural resistance to C. shasta varies among stocks of fish and may even vary among family groups. Riverine conditions (e.g. temperatures, flow, and dissolved oxygen) affect a fish’s ability to resist infection. The degree and severity of infection may be linked to how far and how long an organism has been outside optimal conditions.

Dr. Hallett and her colleagues have been involved extensive studies of C. shasta in the Klamath River, where they established a monitoring program over a decade ago. They are applying those methods/approaches to other systems to better understand host/parasite dynamics with an aim to inform management options and reduce salmonid population-level impacts of the parasite. etermine if there are any correlations. A model has been developed but has yet to be validated, which will be part of this proposal.

The OSU/USFWS study demonstrated high C. shasta spore concentrations in the Deschutes River in May 2016 report. The CTWSRO believes we have a problem with pre-spawn mortality in spring Chinook holding in the WSR canyon but have not confirmed yet. Redd numbers are very low compared to WSNFH escapement of wild spring Chinook (e.g., 5.7 fish/redd pre-2010 to 18 fish per redd 2010-2016, Figure 2). It is likely that spring Chinook from WSR are becoming exposed to C. shasta in the Deschutes River as juveniles and/or adults, returning to WSR, holding in warm stream temperatures (Figure 3), dying prior to spawning from C. shasta and/or egg survival is reduced for females exposed to high stream temperatures (McCullough 1999).

Dr. Hallett has been in collaboration with another of our colleagues, Ken Lujan, microbiologist with the USFWS Lower Columbia River Fish Health Center, and Terry Schrader at Oregon Dept. of Fish and Wildlife (ODFW). They completed a two-year study that combined sentinel fish exposures and water sampling in the Deschutes and Willamette rivers in 2015 and 2016. This is an important contribution as it has provided pilot-level results for spring Chinook in control and treatment groups for spring Chinook exposed to C. shasta, BKD, and fungi and quantified C. shasta spores at a number of sites longitudinally in the Deschutes River. The proposed work for 16-Warm-05 will build on this study and provide insight to likely pre-spawn mortality of spring Chinook in WSR. The CTWSRO (or K. Lujan at Bonneville Dam) will be collecting samples and sending them to Dr. Hallet for analysis. Results will be provided to Dr. Baker as available to assist with interpretation of other data being collected at Warm Springs, and a fin