Walking by the riverside, Jerri Bartholomew passes hovering stoneflies and stalking herons, keeping her eyes on the water. Bartholomew is a research scientist—studying salmon and the parasites that infect them. She’s also an artist—casting glass into forms inspired by her river work.
Bartholomew came to Oregon State University after completing an undergraduate degree in biology at Penn State. She thought that Corvallis was a good place to be, but it was a fish disease class taught by distinguished professor John L. Fryer that reeled her in. Soon she embarked on a Ph.D., under Fryer’s direction.
“Oregon is a long way from Pennsylvania,” said Bartholomew, but “here is where I could do the research I wanted to do, and this place became home.”
Thirty years later, the watery world of salmon continues to suffuse her work, her art, and her awareness. Bartholomew is now the director of OSU’s John L. Fryer Salmon Disease Laboratory.
The fish lab, unassuming yet innovative, is one of the preeminent facilities in the world to study fish pathogens, and it is here that Bartholomew seeks clues to why salmon populations get sick and how she might help bring them back to health.
Salmonids (salmon and trout) have had a difficult run of it here in the Pacific Northwest. In the Klamath River Basin system, weak salmon returns coincide with severe parasite infections. Most of Bartholomew’s current work focuses on the microscopic parasite Ceratomyxa shasta, which infects salmonids from northern California to Alaska.
These parasites have a complex life cycle involving two hosts that never actually come in contact with one another: tiny segmented worms that live at the bottom of rivers, and the fish swimming above. The worms, quietly waving among dark, slippery rocks, release puffs of spores into the river. These tiny spores drift in dilute clouds, infecting salmon on contact. When the sick fish die, billows of an altogether different form of spore emanate from their bloated bellies, settling down onto uninfected worms and reinitiating the cycle.
To get a clearer idea about the dynamics of this interaction, Bartholomew and her team visit sites in the Klamath, taking water, fish, and worm samples. It’s clear from the data they’ve collected so far that when water temperatures are high, water flow is low, or parasite spore levels are high, salmon have a harder time resisting infection. Also, some fish stocks are more resistant to the parasite than others, and some strains of the parasite are more virulent.
“It’s exciting to look at the molecular basis of immune function and parasite evolution,” said Bartholomew, “but I don’t want to spend all my time studying the infection; I want to do something about it.” The fish are ever more susceptible to infection due to rising water temperatures and changes in seasonal flows.
Bartholomew is looking for ways to reign in parasite dispersion and foster salmon survival. She works closely with biologists from the Oregon Department of Fish and Wildlife (who assist with studies on Oregon’s Klamath River tributaries), the U.S. Fish and Wildlife Service (who track infection rates in wild salmonid populations), and the Yurok and Karuk tribes (who collect Klamath water and worm samples), pulling together their data sets and her own.
The results will be part of an environmental review by the U.S. Department of the Interior and for Congressional consideration to remove four dams and begin large-scale restoration of the Klamath River. “We are being asked what might make a difference for the fish,” said Bartholomew. She’s watching the water to learn the answer.
~ Megan McKenzie