ROSEBURG, Ore. — Historically, spring chinook have returned to the South Umpqua River by the thousands, spending time in deep, cool pools in the summer before spawning in the fall.
Greg Huchko with the Oregon Department of Fish and Wildlife said his department has been doing snorkel counts of the species for the past 40 years.
This year they counted 28 fish that had returned to their natal pools — the second lowest since the department started recording the numbers.
“Obviously it’s been a red flag for us,” Huchko said.
Loss of spawning habitat, warming river temperatures, predation and ocean acidification are all contributing to their decline.
Huchko said ODFW would like to see the population around 600, although the species has been hovering around 170 on average.
He said if there are successive years of abysmally low numbers going into the future, it could be catastrophic.
“If that were to perpetuate, then the likelihood of extinction is there and is real,” Huchko said.
Jeff Dose, a retired fish biologist with the Umpqua National Forest, said one year’s return doesn’t necessarily mean there’s going to be 28 again next year.
“There could be 300 next year,” Dose said. “We don’t know what’s going to happen next year. There may be none next year; we don’t know.”
He said the numbers suggest that the species may hang on for a while at low numbers.
Dose said the accounts that point to thousands of fish once being in the South Umpqua in the early 1900s are estimates based on harvest records.
Spring chinook salmon return to their spawning grounds from the ocean in February and March. As temperatures rise, the fish start looking for pools to stay in during the summer before they spawn in September and October.
Unlike their spring counterparts, fall chinook start entering the rivers in September and spawn shortly after.
A study released by the University of California Davis last year was confirmation of what many already knew — these fish are unique.
Stan Petrowski, president of Umpqua Watersheds, said the fundamental assumption was that spring and summer chinook were all one species, but DNA testing proved otherwise.
Through a DNA analysis, the authors of the study found that early-migrating fish like spring chinook and summer steelhead depend on a single gene that makes them head inland sooner than their fall and winter counterparts. It also found that the gene evolved once in each species, meaning that if they go extinct, they’re not likely to re-evolve.
The findings could have implications for future management of spring chinook, which aren’t currently considered distinct from fall chinook — a species that is doing relatively well in the North Umpqua River with thousands returning each year.
Petrowski said Umpqua Watersheds is working with the Forest Service to improve habitat.