A3-inch fish that has slowly infiltrated the Deschutes Basin over the past few decades could prove key to understanding the impact of pollution in Central Oregon’s waterways.

“They’re beloved, they’re widespread, they’re easy to relate to and they can tell us a lot about water quality,” said Ann Petersen, a biology instructor at Oregon State University-Cascades.

Building off work that began during her time at the University of Oregon, Petersen spearheaded The Stickleback Project, a lab focusing on a common species of fish known as threespine stickleback, after arriving in Bend in 2015. Because the fish are well-studied by researchers and have comparatively similar organ structures and reproductive cycles to humans, stickleback are often used by researchers as a “sentinel species,” an organism that can be used to model potential risks to humans.

Because the fish exist in large numbers throughout the Upper Deschutes, Petersen and her students are studying stickleback populations at seven different locations along the river, as a way to determine whether the fish are impacted by pollutants in the river that could also affect humans.

“The Deschutes River is just chock-full of stickleback,” Petersen said. “It’s kind of a living lab.”

If the hypothesis is proved correct, researchers looking at stickleback could detect high levels of pollutants in the river with significantly less cost and effort than by constantly measuring water quality.

On Tuesday, Petersen will lead a sold-out presentation for the public on the lab’s work on stickleback, and how the research can be extended to the rest of Oregon’s waterways.

“Can we use the stickleback in the Deschutes as a canary in a coal mine?” Petersen said.

Not only does Petersen’s lab provide information about the environmental health of the river, but it also gives undergraduate students at OSU-Cascades experience with graduate-level work that can give them a leg up when applying to other programs.

“It’s given me the opportunity to learn a lot more than I would in a classroom,” said Anthony Brande, a junior at OSU-Cascades who is taking the lab.

Threespine stickleback are found across the Northern Hemisphere, from Japan to Alaska. Petersen said the species is popular in England, in part because of the elaborate mating dances that males use to attract females to their nests.

Stickleback are found off the Oregon coast, and in the Willamette and Mackenzie rivers, but hadn’t been spotted in the Deschutes Basin prior to the 1990s. Twenty years ago, an Oregon Department of Fish and Wildlife biologist described the small fish as taking over Crane Prairie Reservoir in the upper Deschutes, possibly brought there by an angler, according to The Bulletin’s archives.

While Petersen said a disease lowered the population in the reservoir since then, the species has proliferated in other parts of the upper and middle segments of the Deschutes River.

While they’ve spread throughout the river system over the course of decades, Petersen said individual fish most likely stay in the same basic stretch of river, which would mean that they reflect the effects of chemicals and pollutants in a particular portion of a river.

According to a 2016 report from the Oregon Department of Environmental Quality, 18 individual pollutants were found in the watershed two years prior, including herbicides and pesticides associated with agriculture.

Petersen said additional pollutants found in the river come from plastic liners, and the confluence of the Little Deschutes River and the Deschutes River has been a source of pollutants in the past.

She said that several of the pollutants found in the water are known to affect the endocrine system, which includes the thyroid and the pancreas, and utilizes the liver, kidney and gonads. The pollutants, Petersen said, could cause liver disease and other ailments.

“They may be part of, truly, an emerging health crisis around the world,” she added.

To study the fish, the team will place baited minnow traps at seven locations along the upper and middle Deschutes, along with a control population in Tumalo Creek. Once the fish swim into the trap, they’re anesthetized and brought into the lab, where they’re dyed and examined under a microscope.

While Petersen cautioned that the lab’s work remains based on a hypothesis, the differences between a tissue sample from a fish that lived in a polluted area of the river compared to the control population are visible even to the untrained eye. The liver of a fish in an area with known pollutants had significantly more white fat cells, suggesting the possibility of liver disease. Petersen said other impacts to fish include changes to thyroids, reproductive abnormalities and occasional tumors.

For students, the lab provides an opportunity to work on a project that might otherwise be reserved for graduate students. Deidre Heil, a senior taking part in the lab, said she anticipates that having this type of lab experience will give her a leg up when applying for a Ph.D. program.

“It gave me a background, and the skills that I needed to apply for that program,” Heil said.

Ideally, the lab will expand its research to examine stickleback populations in other rivers in Central and Eastern Oregon. Peterson said a small handful of the fish have been found in the John Day River.

Additionally, Heil recently received a fellowship from the nonprofit Central Oregon Flyfishers to determine if stickleback living in the Crooked River are affected. Heil will try to trap and study 50 stickleback from four sites along the river.

“I’m basically doing a masters program in an undergraduate program,” Heil said.

— Reporter: 541-617-7818, shamway@bendbulletin.com

Editor’s note: This article has been corrected. The original version misstated Ann Petersen’s title. The Bulletin regrets the error.