Deschutes River Ceratonova Shasta Presence Evaluation I

This project investigated the presence, abundance, and sources of Ceratonova shasta (C. shasta), a myxosporean parasite that infects salmonids in the Pacific Northwest through water samples. The next phase (16-Warm-05) will continue the investigation to indicate inter-annual variation and enhance our ability to evaluate climate variables, such as water temperature and streamflow. These will be 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. In a pilot study, the USFWS/OSU (2016) found low concentrations (<2 spores/liter) of C. shasta spores in the Deschutes River downsteam of Warm Springs River (rkm 135), Trout Creek (rkm 141), Bakeoven Creek (rkm 82), and Buckhollow Creek (rkm 69). They found higher concentrations in the Deschutes River downstream of Pelton Re-regulating Dam (rkm 161, 13.8 spores per liter), Oak Springs (rkm 76, 4.5 – 41 spores/liter), and at Heritage Landing (mouth, 3.8 – 131.8 spores/liter); 10 spores/liter is considered high.

The approach of this study is to monitor C. shasta spore densities and determine the genotype of C. shasta in two index sites in the Deschutes River and perform two longitudinal studies per year in 2017 (15-Warm-04) and 2018 (16-Warm-05). Included in this study (16-Warm-05) were two longitudinal water-sampling events (spring and summer) at ten sites in the Deschutes River in 2017 and weekly or bi-weekly sampling at two sites from March through September 2017.

It is important to know which genotype of C. shasta is present in the Deschutes Basin as Chinook are more susceptible to genotype I and coho are sensitive to genotype II. Knowing the genotype of C. shasta present will be useful in developing risk assessment for migrating juvenile and adult spring Chinook. This will be accomplished by performing PCR analysis on filters (from water samples).

Water sampling:

Water samples were collected at ten sites from the town of Bend to Heritage Landing at the mouth of the Deschutes River. Many of the sites are named for the stream for which is converging with the Deschutes River but all nine samples were collected within the Deschutes River. Two of the ten sites were index sites with weekly or biweekly samples collected but also collected at the same time as longitudinal samples. These include Oak Springs, which was sampled weekly, and Pelton, which was sampled bi-weekly. In addition, during longitudinal sampling, water samples will be collected upstream and downstream of the mouth of the Deschutes for reference. All sites making up the longitudinal profile of C. shasta in the Deschutes River, plus reference sites outside the mouth, were sampled once in the spring and once in the summer 2017. At each sampling location, quadruplicate samples were collected and the spores of C. shasta per liter reported as an average for the site. For each sample site and subsample, one-third were genotyped. The method for which water samples are collected, C. shasta spores were quantified and genotyped are as follows:

At a given site, four one-liter water samples are collected in knee-deep water. Water temperature, day, time is recorded. Water samples are kept on ice until filtered at the office. Samples are filtered by vacuum pump (400 psi) using Millipore MF filters (5.0¿m). Filters will be folded using forceps and inserted into 2.0ml microfuge tubes, which will be frozen until analyzed. Filters will be analyzed by quantitative polymerase chain reaction (PCRq) for C. shasta spore densities. For every one out of three samples DNA will be extracted, amplified and genotyped by PCR assay.

) Because of declining trends of spring Chinook in the Deschutes Subbasin and risk of infection to C. shasta, this study is important for documenting seasonal and annual C. shasta sprore densities and genotype presence. Results indicated higher levels of C. shasta spores during spring when juveniles are outmigrating and adults are returning. This could lead to infection and become virulent during summer when adults hold in tributaries prior to spawning in fall. The genotype of C. shasta present and most common is type 1, which affects Chinook. Spring Chinook are more vulnerable to the infection than fall Chinook due to river temperatures when fish are migrating, holding, and spawning. Results from longitudinal samples collected between 2016 and 2018 indicated seasonal and annual variation in C. shasta spore densities and genotype present. Low densities of C. shasta spores from water samples in Warm Springs River in 2017 and 2018 indicated that spring Chinook were becoming infected in the Deschutes River. As climate change progresses towards ever-warmer summers when spring Chinook hold, this information will be helpful in assessing risk in management decisions and restoration actions.