It’s Springer Season, But Not on the Deschutes

Photo by Brian O’Keefe

Dwindling Kings

Spring Chinook are in trouble everywhere, but they’re in a special kind of trouble on the Deschutes River. For spring kings, reintroduction above the three dams that comprise the Pelton Round Butte Complex has been a dismal failure. According to Portland General Electric’s website, since 2012, spring Chinook returns attributed to the reintroduction project have averaged just 36 fish per year. In 2023, only 13 came back. In 2018, just five. 

Unlike spring Chinook up and down the west coast, where a combination of hatchery practices, overfishing, habitat loss, and climate chaos has placed springers in general peril, these fish on the Deschutes have a specific, identifiable threat: a parasite that kills them.

Deadly Parasite in the Deschutes  

For several years now, the DRA has been monitoring the occurrence  of Ceratonova shasta, a parasite that causes mortality to spring Chinook.  Sampling done prior to the 2010 start of Selective Water Withdrawal Tower operations found no evidence of the presence of C.shasta. The change in flow regime, from cool, clean water released from the depths of Lake Billy Chinook through the outlet works at Round Butte Dam, to warmer, nutrient-rich and  polluted water from the surface of the reservoir, is the likely culprit. 

C. shasta is a microscopic Myxozoan parasite that relies on a host polychaete worm for part of its complex life cycle. The worm carries C. shasta, which sheds spores into the water. The spore, in turn, rides the river’s current, and infects fish that it encounters, eventually attaching itself to tissue in the fish’s gastrointestinal tract. Infection is presumed at spore densities of 10 per liter. A 2015 study by ODFW and Oregon State University measured over 300 spores per liter at a site near Oak Springs, not far from the city of Maupin. Juvenile spring Chinook exposed to Deschutes water at this site had a very high mortality rate due to C. shasta infection.

The overall effect increases in C. shasta could well be having on overall spring Chinook numbers in the Deschutes is alarming. The vast majority of spring Chinook in the Deschutes basin return to the Warm Springs River and are counted with precision at Warm Springs National Fish Hatchery. 

Follow the Science

Prior to the advent of Tower operations, from 1975 to 2009, annual wild spring Chinook returns counted in the Warm Springs River averaged 1,279. From 2012 to 2021, the average dropped to 415. Worse, the number of spring Chinook required to make a redd—the spawning nest that a female salmon makes in the riverbed—in the Warm Springs River rose from an average of 4 as counted from 1977 to 2009, to over 13 from 2009 to 2016 and has been measured as high as 22 adults per redd. This metric indicates a deeply concerning rise in pre-spawning mortality that could very well be attributable to increased C. shasta infection.    

On its website PGE claims, “we continuously collect data and keep up with the latest science in order to review our successes and setbacks. All of this helps ensure that we are on the path to restoring a healthy Deschutes basin—a goal and long-term vision we share with our partners.”

The Tower Doesn’t Work

A truly honest review of fish re-introduction would deem it an utter and complete failure.  Not only is re-introduction above the dams not working, this failure is coming with an increasingly large and negative impact to the fish and ecology of the lower Deschutes.