Spring chinook loss tops 1 million
TRAIL — Cole Rivers Hatchery workers are pulling out all the stops to coddle the remaining Rogue River spring chinook salmon fry that have survived an algae outbreak that so far has killed more than 1 million infant chinook.
Hatchery workers this week finished disinfecting the hatch house’s entire water system and abandoned portions of the hatch house where the algae outbreak, discovered Dec. 7, set off a litany of fish deaths whose numbers still inch up daily at the 46-year-old hatchery on the Rogue River near Trail.
Also, the 1.25 million spring chinook fry now in two outside, open-air ponds are getting light dosings of salt to their water as a way of soothing the stressed fish.
“We’re doing everything we can to baby these guys, treat them with velvet gloves,” hatchery Manager David Pease said.
They have also stepped away from the stacked trays for raising the first 60,000 Rogue coho sac fry, instead putting them in two large glass jars with about four times the water flow to keep the brown algae, called diatoms, from choking off water flow and attacking the tiny fish.
Clogged trays were responsible for killing about 460,000 chinook Dec. 7, and the tiny chinook dying in the ensuing days have run the losses up to about 1.1 million of the 3.3 million eggs spawned last fall.
Cole Rivers now has on hand less than 75 percent of its target of 1.7 million spring chinook smolts released annually as mitigation for lost wild spring chinook spawning habitat by the building of Lost Creek dam in 1977.
Already ODFW plans to keep as many of these chinook alive as possible by ponding them in lighter densities to reduce stress. Plans are to grow these fingerling to larger-than-normal smolt sizes in hopes of boosting their survival rate when released — some in October and the rest in March 2020.
“We’re trying to maximize survival and minimize impacts on future angling,” said ODFW Rogue District fish biologist Dan Van Dyke.
A traditional August release has been scrapped, as were plans to stock excess spring chinook fry in Fish Lake and elsewhere.
About 30 percent of this year’s surviving brood are expected to return to the Rogue in 2021, with about 60 percent in 2022. The rest will return either earlier as jack salmon or later as larger, 5-year-old chinook prized by anglers for their size and taste.
Hatchery returns are key to the Rogue because anglers can keep only fin-clipped hatchery spring chinook during the bulk of the run. Compounding the issue is that hatchery returns have ebbed over the years, and their poor showing in catches have caused angler ire over the years.
But the shortfall of hatchery chinook fry doesn’t necessarily mean poor hatchery returns in future years, Van Dyke said. Good ocean survival rates can lead to good future returns even if hatchery releases come up short of their targets, he said.
Meanwhile, the Army Corps of Engineers plans to assemble a multi-disciplinary team later this month to do an overall assessment of the entire Cole Rivers facility, including the water system, said Tom Conning, a Corps public affairs specialist in Portland.
The Corps considers the investigation into the die-off open, and they have reviewed ODFW data about the circumstances surrounding the incident, Conning said.
“We’re working with ODFW to assess the facility and work on a solution together,” Conning said.
In late December, Corps officials said they had requested money in the agency’s 2019 fiscal budget to address work at Cole Rivers, but they have declined to reveal how much money is in that request until the 2019 federal budget is signed by President Donald Trump.
Cole River technicians still spend about 45 minutes each morning culling dead fry from the ponds, with Friday’s count down to 2,339 dead salmon, Pease said.
The so-called “picking morts” takes about 45 minutes; three weeks ago it took most of the day.
Pease said the pall that had descended over the hatchery grounds the past month seemed to have lifted a bit with the disinfecting of the water system.
“Everyone was a little more upbeat, I’d say,” Pease said. “It was like they were battling the beast.”