Wednesday June 17, 2026
Herald and News —
Dead juvenile Chinook salmon have been found on sections of the lower Klamath River and near the Oregon-California border. Scientists believe the deaths are caused by parasites that are proliferating because of the low winter snowpack and warm spring temperatures.
“We’re seeing dead and dying fish,” Sascha Hallett, a fish parasitologist and associate professor at Oregon State University’s Department of Microbiology, said in a telephone interview. “Everybody wants to understand what is occurring and how we can prevent it.”
Hallett said studies indicate the die-offs are being caused by a parasite, Ceratonova shasta. She said OSU researchers, in cooperation with state and federal agencies, tribes, and other agencies, believe the low winter snowpack and warmer than average spring temperatures accelerated the proliferation of the parasites, which thrive in warm, slow-moving water and attack the intestinal lining of young salmon.
Hallett said searchers are conducting sentinel, or surveillance, fish exposure studies by placing juvenile fall Chinook and rainbow trout in river cages for 72 hours and monitoring them for disease. She said tests done in May showed low immediate mortality, but emphasized that infection progression takes weeks.