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FY 2016 Program Highlights


Scientists first notice declines in one of Central Oregon's most culturally and economically important salmon runs, then take colletive action identify and solve the problem.
Using the Power of Collaboration to Combat a Dangerous Fish Parasite
by Sean Connolly and Ben McLean, Fish and Aquatic Conservation Program

In 2014, Service staff from the Warm Springs National Fish Hatchery and Lower Columbia River Fish Health Center noticed that adult spring Chinook salmon were returning to the hatchery with potentially lethal infestations of Ceratonova shasta, a microscopic fish parasite. While C. shasta is native to the Pacific Northwest, historically it’s been more of a problem in southern Oregon rivers. The discovery of elevated levels of the parasite in the Deschutes River Basin was worrisome, especially since it was impacting a salmon run culturally important to tribal fish harvests and valued by recreational anglers.

Further reviews of salmon monitoring data revealed that hatchery salmon -- both juveniles and adults -- were dying in large numbers as they migrated to and from the hatchery through the Deschutes system. Service scientists found that less than half of all juveniles released from Warm Springs NFH in spring were passing over Bonneville Dam, and adult losses prior to spawning were higher than expected. The results were startling, and added an extra challenge to the hatchery’s goal to protect nearby wild salmon runs by providing a sustainable hatchery program.

Warm Springs National Fish Hatchery raises and releases spring Chinook salmon anually to support tribal harvests and provide recreational angling opportunities. In 2014, Service staff noticed increased numbers of returning adults infected by the C. shasta parasite.
Credit: USFWS

Service scientists began to suspect that Deschutes River Chinook were facing a new double-whammy of climate change-induced increases in river temperatures that in turn were amplifying the spread of the C. shasta parasite, which can cause severe --even lethal -- organ damage to infected fish. But they needed proof first.

Studying -- and ultimately controlling -- pathogen outbreakson basinwide scale is an immensely complex task, requiring a coalition of researchers, fisheries managers, and water managers to work together. The Service took a leadership role in the key first step: organizing the study that would verify C. shasta as one of the primary culprits contributing to the recent increases in spring Chinook losses.

Ceratonova shasta is a microscipic parasite tha infects the intestines of juvenile and adult salmon and trout, sometimes with lethal results. Credit:

But the agency couldn’t -- and didn’t want to -- do all of the sampling and analysis work alone. Instead, it rallied a group of stakeholders to help with research and monitoring: the Confederated Tribes of the Warm Springs Reservation, ODFW, Pacific Gas and Electric, which owns and operates the Pelton/Round Butte Hydroelectric Complex, and Oregon State University. Each partner not only had a stake in the game, but also brought expertise and experience that enhanced the Service’s investigation.

The three-year study recently concluded in 2016. But already the data collected and analyzed by the partners has shown that C. shasta numbers in the waters of the basin greatly exceed levels that are known to be lethal to salmon. More importantly, the work has shown that parasite numbers are driven by water temperatures and suggests that man made and climate driven temperature changes  in the lower Deschutes are indeed the likely cause for the severe increase in, and the severity of, C. shasta infections.

Minimizing the effects of C. shasta on Deschutes River spring Chinook will increase survival of both juvenile and adults, good news for non-tribal and tribal anglers (shown here)

Study results also provide insight into the seasons and locations where levels of the parasite are likely to be high. The data are already informing discussions and key decisions about how to better time fish releases, find strategic locations for fish releases, and manage river water to help contain the parasite and balance the needs of both fish and the local communities that depend on the Pelton/Round Butte Complex’s hydropower.

So while C. shasta, like other native parasites, may be impossible to fully eradicate, the Tribe, fish managers and hydropower operators in the Lower Deschutes River now have two new weapons for controlling its spread in the future. The first is the science needed to guide effective management decisions, for water and fish. The second is equally powerful: a model of collaboration that can make those decisions happen. That’s not only good news for the fish, but for tribal and sport fish anglers that count on healthy Chinook returns in one of the Northwest’s most iconic rivers.


Last Updated: May 25, 2017
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