Oh, what a difference a tui chub makes.

The discovery of a single tui chub in Diamond Lake in October — nine years after a $5.6 million eradication effort — has state fish managers going all in on an effort to keep history from repeating itself.

The Oregon Department of Fish and Wildlife plans to stock as many as 25,000 fish-eating tiger trout in the eastern Douglas County lake this spring, and it will follow up with a crew literally working day and night next summer to search for more of these unwanted invaders.

"I'm hoping it was the only tui chub, but I'm operating on the assumption that it wasn't," says Greg Huchko, ODFW's Umpqua District fish biologist heading the effort. "I'm hoping, in a year or two, this becomes a non-issue."

The last time tui chub were discovered in the lake was 1991, and before agency biologists could get a coordinated and funded plan in place, the population hit 30 million.

It wasn't until 2006, when 90 million tui chub had altered the lake's ecosystem so dramatically that a toxic blue-green algae bloom had the lake glowing like an underwater aurora borealis, that chemical poisoning of the lake became a reality.

That was the equivalent of letting an alcoholic hit rock bottom before drying him out. This time, the patient is hitting rehab after his first beer.

"The playing field's a little different now because we were able to catch it early," Huchko says. "This isn't ideal, but we want to be as proactive as we can."

When not under tui chub attack, Diamond Lake is the crown jewel of south Cascades trout lakes, historically drawing more than 100,000 angler-days for its stocked rainbows that grow fast and large thanks to the lake's bountiful insect population.

In 1954 and again in the early 1990s, some nitwit illegally used chubs as live trout bait, and escaped chubs spawned and exploded. The plankton eaters eventually out-competed stocked trout for food and space, and eventually they tipped the scales in favor of toxic blue-green algae blooms.

That ultimately led to a state, federal and private partnership that studied and funded the use of rotenone to kill off everything in the lake in 2006, then restart from scratch in 2007.

That lengthy effort last time, Huchko says, laid the groundwork to react quickly after October's capture of a single 7 1/2-inch, 4-year-old tui chub.

While it is too young to have been a rotenone survivor, the origin of the chub remains a mystery.

But what isn't a mystery is that history has proven Diamond Lake could easily again turn into a troutless, toxic, cubic zirconium version of itself without fast action.  

"It's not just a fishing issue," Huchko says. "It's a huge water-quality issue, as well."

The agency plans to stock 18,000 to 25,000 tiger trout — a sterile brown trout/brook trout hybrid known to prey on smaller fish. They've been stocked since 2012 in Fish Lake, and they've shown success at eating chub, but they are not going to eat that lake chub-free.

Likewise, land-locked spring chinook salmon and other so-called "pisciverous" strains of rainbow trout — even a hybrid bred just for Diamond Lake — failed to keep the chub population from exploding.

"We've tried a lot of different options in the past and never really had great success with the rainbow varieties we've tried," Huchko says. "I'm just hopeful this time that we can keep things at bay for a while."

Huchko hopes to double-down on tiger trout by adding two seasonal employees this summer to undertake myriad duties to keep track of tiger trout and snuff out chub.

They'll run a smolt trap at the lake's outlet at Lake Creek to look for chub and see whether tigers are migrating out. They'll do beach seining and trap netting for chub and even do nighttime electro-shocking of the lake's shallows in search of more invaders.

The tiger trout will be purchased from a private hatchery in Utah for about a buck apiece, Huchko says. The trapping and electro-shocking, as well as helping out on creel surveys for tiger trout, will run about $35,000.

Huchko hopes to pay about three-fourths of the cost with state and federal grants. The Umpqua Fisheries Enhancement Derby will also help raise money by holding a “fish frenzy” at its annual derby banquet and auction Jan. 29.

If this seems like overkill for one tui chub, Huchko has to look no farther than his desktop for evidence otherwise.

On it sits a copy of the federal environmental study that led to the last rotenone treatment. On its cover is an aerial photo of the neon-green glow from one of Diamond Lake's toxic algae blooms of the mid-2000s.

"That," he says, "is the doom and gloom."

Reach reporter Mark Freeman at 541-776-4470 or mfreeman@mailtribune.com. Follow him at www.twitter.com/MTwriterFreeman.