GOLD HILL — State fish biologists are trying to artificially recreate a long-lost portion of the Rogue River's famed spring chinook salmon run — one fish-stocking truck at a time.
The Oregon Department of Fish and Wildlife released 50,000 yearling spring chinook Wednesday that were raised at Cole Rivers Hatchery so they can head to sea as smolts a half-year later than normal Rogue spring chinook.
These fish were raised to emulate the wild chinook that once spawned in the far upper Rogue Basin streams whose access was forever blocked in the 1970s by the building of Lost Creek Dam.
The hope is these fish will live longer in the ocean, grow larger and return to the upper Rogue earlier in the spring than fish released from the hatchery each August through October.
Biologists believe that the very cold waters of the far-upper Rogue and its tributaries such as the South Fork Rogue retarded the growth of wild spring chinook to where it took a year or more for them to get to the 5- to 8-inch size that triggered their migration to the ocean as smolts.
"We want our hatchery run to reflect as closely as possible the life history of the fish that it is supposed to replace — the wild fish that used to spawn well up into the South and Middle forks of the Rogue," says Dan VanDyke, ODFW's Rogue District fish biologist.
"This change in the hatchery release adds some of that life history back," he says.
The young chinook, which sport clipped adipose fins like all hatchery spring chinook, were trucked to Gold Hill and released there to reduce their potential impact on infant wild chinook now in the upper Rogue, VanDyke says.
ODFW used to release some of its Rogue hatchery spring chinook smolts in March, but that program was discontinued in 1983 amid concerns over negative impacts to wild spring chinook fry hatching in the upper Rogue, VanDyke says.
VanDyke was able to rekindle the program last year when the agency cut back on the number of hatchery coho salmon it releases, freeing up production room for about 1.7 million spring chinook.
The fish are released in an attempt to mitigate the loss of upper Rogue spawning grounds caused by the dam's placement, which cut off about 30 percent of wild spring chinook spawning grounds.
Some of the fish released Wednesday had coded wire tags imbedded in their snouts so they can be tracked as adults to ensure they don't overly stray onto wild fish spawning grounds if they're not caught by anglers or return to the hatchery, VanDyke says.
When hatchery workers raised the spring-released chinook in the late 1970s and early '80s, some of those fish died from disease outbreaks. But this year's crop has been easy to raise, hatchery Manager David Pease says.
"We just hold onto them a little longer," Pease says. "The only concern is disease, and so far there's been no problem."
VanDyke says he expects at least five years' worth of spring releases to evaluate whether it's a success.
"I'd like to see this continue well into the future," he says.